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Chinese cabbage, belonging to Brassica rapa species, is an important vegetable in Eastern Asia. It is well known that Chinese cabbage is quite recalcitrant to genetic transformation and the transgenic frequency is generally low. The lack of an efficient and stable genetic transformation system for Chinese cabbage has largely limited related gene functional studies. In this study, we firstly developed a regeneration system for Chinese cabbage by optimizing numerous factors, with 93.50% regeneration rate on average. Based on this, a simple and efficient Agrobacterium-mediated genetic transformation method was established, without pre-culture procedure and concentration adjustment of hormone and AgNO3 in co-cultivation and selection media. Using this system, transformants could be obtained within 3.5 to 4.0 months. Average transformation frequency is up to 10.83%. The establishment of this simple and efficient genetic transformation method paved the way for further gene editing and functional studies in Chinese cabbage.

Cytochrome P450 genes are involved in the catalysis of various reactions, including growth, development and secondary metabolite biosynthetic pathways. However, little is known about the characteristics and functions of the P450 gene family in Chinese cabbage (Brassica rapa L. ssp. pekinensis). In this study, we identified 258 non-redundant members of the cytochrome P450 gene superfamily in Brassica. rapa from Brassica database (http://www.brassicadb.cn). We also did transcriptomic data mining derived from abiotic/biotic stresses and developmental related RNA-seq in Chinese cabbage. These differentially expressed genes (DEGs) were involved in cadmium (Cd) detoxification, salinity tolerance, calcium signaling transduction and homeostasis, pathogen triggered immunity and leafy head formation in Chinese cabbage. These P450 genes are essential candidates for a better understanding of the mechanism of P450 genes, which help Chinese cabbage adapt to environmental changes.

Since Chinese cabbage is consumed fresh, its wholesale price varies with the total amount supplied on the market. However, in these days, climate variability presents a large threat to sustainable Chinese cabbage production in South Korea. To manage Chinese cabbage production well under unexpected weather conditions, it is important to study the impacts of climate variability on Chinese cabbage economic yields in South Korea. In this study, 2-year field trials were conducted in multiple locations across seven provinces in South Korea. The collected morphological data from 24 different varieties were used to develop a yield prediction model using a machine learning technique. Three Chinese cabbage groups were carried out through the clustering analysis, and a yield model was developed for each cluster group. The developed model was used to predict the cabbage economic yields under different combinations of climate change and cropping management plans. According to simulation results, Group 1 had the shortest growing degree days and produced higher yields than the other two groups. However, the overproduction of Group 1 led to a price reduction in the market of (USD(0.04–0.08) per kg), which suggested that producing Group 2 of (USD(0.31–0.96) per kg) is more beneficial to farmers. Based on the production results of the groups, their revenue varied by location and cropping management. The results of this study provide farmers with a better understanding of the relationship between production and economic benefits in future climate change scenarios.

Clubroot disease is a soil-borne disease caused by Plasmodiophora brassicae that leads to a serious yield reduction in cruciferous plants. In this study, ergothioneine (EGT) was used to culture P. brassicae resting spores, the germination of which was significantly inhibited. Further exogenous application of EGT and P. brassicae inoculation in Chinese cabbage showed that EGT promoted root growth and significantly reduced the incidence rate and disease index. To further explore the mechanism by which EGT improves the resistance of Chinese cabbage to clubroot, a Chinese cabbage inbred line BJN3-2 susceptible to clubroot treated with EGT was inoculated, and a transcriptome analysis was conducted. The transcriptome sequencing analysis showed that the differentially expressed genes induced by EGT were significantly enriched in the phenylpropanoid biosynthetic pathway, and the genes encoding related enzymes involved in lignin synthesis were upregulated. qRT-PCR, peroxidase activity, lignin and flavonoid content determination showed that EGT promoted the lignin and flavonoid synthesis of Chinese cabbage and improved its resistance to clubroot. This study provides a new insight for the comprehensive prevention and control of cruciferous clubroot and for further study of the effects of EGT on clubroot disease.

The accurate spraying of herbicides and intelligent mechanical weeding operations are the main ways to reduce the use of chemical pesticides in fields and achieve sustainable agricultural development, and an important prerequisite for achieving these is to identify field crops and weeds accurately and quickly. To this end, a semantic segmentation model based on an improved U-Net is proposed in this paper to address the issue of efficient and accurate identification of vegetable crops and weeds. First, the simplified visual group geometry 16 (VGG16) network is used as the coding network of the improved model, and then, the input images are continuously and naturally down-sampled using the average pooling layer to create feature maps of various sizes, and these feature maps are laterally integrated from the network into the coding network of the improved model. Then, the number of convolutional layers of the decoding network of the model is cut and the efficient channel attention (ECA) is introduced before the feature fusion of the decoding network, so that the feature maps from the jump connection in the encoding network and the up-sampled feature maps in the decoding network pass through the ECA module together before feature fusion. Finally, the study uses the obtained Chinese cabbage and weed images as a dataset to compare the improved model with the original U-Net model and the current commonly used semantic segmentation models PSPNet and DeepLab V3+. The results show that the mean intersection over union and mean pixel accuracy of the improved model increased in comparison to the original U-Net model by 1.41 and 0.72 percentage points, respectively, to 88.96% and 93.05%, and the processing time of a single image increased by 9.36 percentage points to 64.85 ms. In addition, the improved model in this paper has a more accurate segmentation effect on weeds that are close to and overlap with crops compared to the other three comparison models, which is a necessary condition for accurate spraying and accurate weeding. As a result, the improved model in this paper can offer strong technical support for the development of intelligent spraying robots and intelligent weeding robots.

Leaf flattening plays a vital role in the establishment of plant architecture, which is closely related to plant photosynthesis and, thus, influences the product yield and quality of Chinese cabbage. In this study, we used the doubled haploid line ‘FT’ of Chinese cabbage as the wild type for ethyl methanesulfonate (EMS) mutagenesis and obtained a mutant cwm with stably inherited compact and wrinkled leaves. Genetic analysis revealed that the mutated trait was controlled by a single recessive nuclear gene, Brcwm. Brcwm was preliminarily mapped to chromosome A07 based on bulked segregant RNA sequencing (BSR-seq) and fine-mapped to a 205.66 kb region containing 39 genes between Indel12 and Indel21 using SSR and Indel analysis. According to the whole-genome re-sequencing results, we found that there was only one nonsynonymous single nucleotide polymorphism (SNP) (C to T) within the target interval on exon 4 of BraA07g021970.3C, which resulted in a proline to serine amino acid substitution. The mutated trait co-segregated with the SNP. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) revealed that BraA07g021970.3C expression was dramatically higher in ‘FT’ leaves than that in cwm leaves. BraA07g021970.3C is homologous to AT3G55000 encoding a protein related to cortical microtubule organization. A similar phenotype of dwarfism and wrinkled leaves was observed in the recessive homozygous mutant cwm-f1 of AT3G55000, and its T3 transgenic lines were restored to the Arabidopsis wild-type phenotype through ectopic overexpression of BraA07g021970.3C. These results verified that BraA07g021970.3C was the target gene essential for leaf flattening in Chinese cabbage.

Purple heading Chinese cabbage has become popular in recent years due to its attractive color and health benefits. However, purple varieties remain rare, and the regulation mechanism of anthocyanin accumulation in Chinese cabbage is still largely unknown. By introducing the purple color trait from Brassica juncea, a new purple heading Chinese cabbage cultivar (18M-245) was generated with deep purple leaves at both the seedling and adult stages. Anthocyanin accumulation in 18M-245 increased when grown at low temperatures. FISH and genotyping results showed that the purple trait was caused by an alien chromosome addition line derived from the Brassica B genome. The LDOX coding gene BjuB014115 from the addition line was highly expressed in 18M-245, consistent with the results of anthocyanin accumulation. Meanwhile, several MYB and bHLH transcriptional factors from the Brassica A genome were found to directly bind to the promoter of BjuB014115, suggesting that interactions between the Brassica A and B genomes are involved in the regulatory network of anthocyanin biosynthesis in Chinese cabbage. Our results provide new insights into the regulation mechanism of anthocyanin biosynthesis in purple heading Chinese cabbage.

Simple Summary Biological control is an important direction for pest control in the future, and chemical ecology is an indispensable part of biological control. Therefore, we tested the selection of Spodoptera litura and parasitic wasps on the volatiles of different treatments of cabbage and collected and analyzed the volatiles of different treatments of cabbage. This study found that cabbage was fed by Spodoptera litura to produce volatiles to avoid Spodoptera litura while also attracting Microplitis similis. As a result, some compounds were found to be related to the behavior of Spodoptera litura and Microplitis similis. These results provide a theoretical basis for searching for biological control resources and chemical control. Abstract Plants respond to herbivorous insect attacks by releasing volatiles that directly harm the herbivore or that indirectly harm the herbivore by attracting its natural enemies. Although the larvae of Spodoptera litura (the tobacco cutworm) are known to induce the release of host plant volatiles, the effects of such volatiles on host location by S. litura and by the parasitoid Microplitis similis, a natural enemy of S. litura larvae, are poorly understood. Here, we found that both the regurgitate of S. litura larvae and S. litura-infested cabbage leaves attracted M. similis. S. litura had a reduced preference for cabbage plants that had been infested with S. litura for 24 or 48 h. M. similis selection of plants was positively correlated with the release of limonene; linalool and hexadecane, and was negatively correlated with the release of (E)-2-hexenal and 1-Butene, 4-isothiocyanato. S. litura selection of plants was positively correlated with the release of (E)-2-hexenal, 1-Butene, 4-isothiocyanato, and decanal, and was negatively correlated with the release of limonene, nonanal, hexadecane, heptadecane, and octadecane. Our results indicate that host plant volatiles can regulate the behavior of S. litura and M. similis.

Flavonols and anthocyanins are the two major classes of flavonoids in Brassica rapa. To elucidate the flavonoid biosynthetic pathway in Chinese cabbage (B. rapa L. subsp. pekinensis), we analyzed flavonoid contents in two varieties of Chinese cabbage with normal green (5546) and purple (8267) leaves. The 8267 variety accumulates significantly higher levels of quercetin, isorhamnetin, and cyanidin than the 5546 variety, indicating that 3′-dihydroxylated flavonoids are more prevalent in the purple than in the green variety. Gene expression analysis showed that the expression patterns of most phenylpropanoid pathway genes did not correspond to the flavonoid accumulation patterns in 5546 and 8267 varieties, except for BrPAL1.2 while most early and late flavonoid biosynthetic genes are highly expressed in 8267 variety. In particular, the flavanone 3′-hydroxylase BrF3′H (Bra009312) is expressed almost exclusively in 8267. We isolated the coding sequences of BrF3′H from the two varieties and found that both sequences encode identical amino acid sequences and are highly conserved with F3'H genes from other species. An in vitro enzymatic assay demonstrated that the recombinant BrF3′H protein catalyzes the 3′-hydroxylation of a wide range of 4′-hydroxylated flavonoid substrates. Kinetic analysis showed that kaempferol is the most preferred substrate and dihydrokaempferol (DHK) is the poorest substrate for recombinant BrF3′H among those tested. Transient expression of BrF3′H in Nicotiana benthamiana followed by infiltration of naringenin and DHK as substrates resulted in eriodictyol and quercetin production in the infiltrated leaves, demonstrating the functionality of BrF3′H in planta. As the first functional characterization of BrF3′H, our study provides insight into the molecular mechanism underlying purple coloration in Chinese cabbage.

Background Tipburn, also known as leaf tip necrosis, is a severe issue in Chinese cabbage production. One known cause is that plants are unable to provide adequate Ca2+ to rapidly expanding leaves. Bacterial infection is also a contributing factor. Different cultivars have varying degrees of tolerance to tipburn. Two inbred lines of Chinese cabbage were employed as resources in this research. Results We determined that the inbred line ‘J39290’ was the tipburn resistant material and the inbred line ‘J95822’ was the tipburn sensitive material based on the severity of tipburn, and the integrity of cell membrane structure. Ca2+ concentration measurements revealed no significant difference in Ca2+ concentration between the two materials inner leaves. Transcriptome sequencing technology was also used to find the differentially expressed genes (DEGs) of ‘J95822’ and ‘J39290’, and there was no significant difference in the previously reported Ca2+ uptake and transport related genes in the two materials. However, it is evident through DEG screening and classification that 23 genes are highly linked to plant-pathogen interactions, and they encode three different types of proteins: CaM/CML, Rboh, and CDPK. These 23 genes mainly function through Ca2+-CaM/CML-CDPK signal pathway based on KEGG pathway analysis, protein interaction prediction, and quantitative real-time PCR (qRT-PCR) of key genes. Conclusions By analyzing the Ca2+ concentration in the above two materials, the transcription of previously reported genes related to Ca2+ uptake and transport, the functional annotation and KEGG pathway of DEGs, it was found that Ca2+ deficiency was not the main cause of tipburn in ‘J95822’, but was probably caused by bacterial infection. This study lays a theoretical foundation for exploring the molecular mechanism of resistance to tipburn in Chinese cabbage, and has important guiding significance for genetics and breeding.

SuccessfulAgrobacterium-mediated transformations of Chinese cabbage have been limited owing to the plant’s recalcitrant nature, genomic background and explant necrosis upon infection, which hinders the transfer of T-DNA region into the Chinese cabbage. Consequently, in the current experiment, a stableAgrobacterium tumefaciens-mediated transformation method for Chinese cabbage cv. Kenshin established by employing important anti-oxidants in the co-cultivation and subsequent regeneration media. Four-day-oldin vitroderived cotyledon explants were infected withA. tumefaciensstrain GV3101 harboring the vector pCAMIBA1303. Cotyledon explants exposed to anAgrobacteriumsuspension (OD600of approximately 0.6) for 10 min and then incubated for 3 days co-cultivation in Murashige and Skoog medium containing an L-cysteine + AgNO3combination exhibited the highest β-glucuronidase (GUS) expression (94%) and explant regeneration efficiency (76%). After 3 days, the cotyledon explants were subjected to three selection cycles with gradually increasing hygromycin B concentrations (10 to 12 mg/L). The incorporation and expression ofhptIIin T0transformed plants were verified by polymerase chain reaction and Southern blot analyses. These transgenic plants (T0) were fertile and morphologically normal. Using the present protocol, a successful transformation efficiency of 14% was achieved, and this protocol can be applied for genome editing and functional studies to improve Chinese cabbage traits.

Flavonols and anthocyanins are the two major classes of flavonoids in Brassica rapa. To elucidate the flavonoid biosynthetic pathway in Chinese cabbage (B. rapa L. subsp. pekinensis), we analyzed flavonoid contents in two varieties of Chinese cabbage with normal green (5546) and purple (8267) leaves. The 8267 variety accumulates significantly higher levels of quercetin, isorhamnetin, and cyanidin than the 5546 variety, indicating that 3′-dihydroxylated flavonoids are more prevalent in the purple than in the green variety. Gene expression analysis showed that the expression patterns of most phenylpropanoid pathway genes did not correspond to the flavonoid accumulation patterns in 5546 and 8267 varieties, except for BrPAL1.2 while most early and late flavonoid biosynthetic genes are highly expressed in 8267 variety. In particular, the flavanone 3′-hydroxylase BrF3′H (Bra009312) is expressed almost exclusively in 8267. We isolated the coding sequences of BrF3′H from the two varieties and found that both sequences encode identical amino acid sequences and are highly conserved with F3'H genes from other species. An in vitro enzymatic assay demonstrated that the recombinant BrF3′H protein catalyzes the 3′-hydroxylation of a wide range of 4′-hydroxylated flavonoid substrates. Kinetic analysis showed that kaempferol is the most preferred substrate and dihydrokaempferol (DHK) is the poorest substrate for recombinant BrF3′H among those tested. Transient expression of BrF3′H in Nicotiana benthamiana followed by infiltration of naringenin and DHK as substrates resulted in eriodictyol and quercetin production in the infiltrated leaves, demonstrating the functionality of BrF3′H in planta. As the first functional characterization of BrF3′H, our study provides insight into the molecular mechanism underlying purple coloration in Chinese cabbage.

Relevance.Growing plants in artificial conditions (closed agroecosystems) requires precise regulation of plant growth factors, starting from the first stages of ontogenesis. One of the parameters is the presence or absence of light in the period of seed germination. For most types of cabbage the standard method is germination in the dark, but for freshly harvested seeds (at rest) light exposure is necessary. According to the literature, the mechanisms of the effect of light on seed germination are complex and ambiguous, so the issue needs detailed research.Methods. Therefore, the purpose of this work was to study the germination of seeds of broccoli (Brassica oleracea var. italica Plenck) and Chinese cabbage (Brassica rapa var. chinensis), taking into account the light factor and the simultaneous analysis of antioxidant activity as a marker of changes in metabolic processes.Results. The experiment has revealed a significant increase in the antioxidant activity of the microgreens during germination in the dark compared to germination in the light (in broccoli by 5.5 times, in Chinese cabbage by 4.8 times). Later on, after the seedlings are moved to the light, the differences between the light and dark versions practically disappear. After germination in the light, the antioxidant activity of microgreens in comparison with the original (dry seeds) decreased by 3-3.5 times, while in the dark – on the contrary, increased by 1.5-1.6 times. The final results of germination (germination energy and seed germination) practically do not differ in the versions. In the case of dark germination, the height of microgreens is greater (due to etiolation and stretching in the absence of light), however, later on, the differences in the versions are smoothed out. The biomass of microgreens in the version of light germination on the 4th day after sowing seeds in broccoli is by 9.1% higher, in Chinese cabbage – by 10.5%. In case of Chinese cabbage, differences remained until the end of the experiment (on the 18th day from sowing seeds), in case of broccoli they were smoothed out. Comparison of two kinds of cabbage has showen that broccoli in the closed system of the synergotron forms a much higher aboveground biomass than Chinese cabbage (on the 4th day after sowing – by 37%, on the 18th day – by 75.4% in the dark version).

Chinese cabbage (Brassica rapa) belongs to the Pekinensis Group and is grown annually as a salad crop. It is one of the most important food crops in Eastern Asia and the most widely grown vegetable in China, accounting for more one-quarter of the total annual vegetable consumption in northern parts of the country. It is reported that nitrogen (N), phosphorus (P), and potassium (K) fertilizations play important roles in the physio-morphological traits and yields of Chinese cabbage. However, N, P, and K use in agriculture continues to increase. Excessive application of fertilizers has a harmful impact on the environment. Yet how to improve the irrigation effects on Chinese cabbage growth is still limited. In this study, we firstly selected biochar nanoparticles (BNPs) prepared from corn straw, which had been air-dried and heated in a muffle furnace at 350 °C for 120 min, with K (potassium sulfate), N (calcium nitrate tetrahydrate), and P (sodium dihydrogen phosphate dihydrate) fertilizers. Then, a screening experiment (Experiment I) was performed via the response model to find the best solution for Chinese cabbage growth. Treatment with 2 g/kg of N and 2 g/kg of K for 4 weeks was the optimum application to promote Chinese cabbage growth. Then, a comparison experiment (Experiment II) was carried out to test the best formula for Chinese cabbage growth with or without BNPs. After co-irrigation with N and K for 4 weeks, treatment with a combination of 2 g/kg of BNPs, 2 g/kg of N, and 2 g/kg of K was the optimum formula for Chinese cabbage growth. Plant biomass increased by more than 1796.86% and 32.80%, respectively, in two combined treatments of BNPs and fertilizers as compared to the control treatment. After the addition of BNPs, Chinese cabbage height (aboveground) and the dry weight of belowground biomass in the N + K treatment increased to 10.97% and 20.48%, respectively. These results suggest that BNPs have great potential as a nanocarrier for fertilization as they are highly efficient (over 50% increase), reducing fertilizer use while promoting plant growth. The use of BNPs as a nanocarrier for fertilizers represents a step toward more environmentally friendly agriculture.

Chinese cabbage tipburn is characterized by the formation of necrotic lesions on the margin of leaves, including on the insides of the leafy head. This physiological disorder is associated with a localized calcium deficiency during leaf development. However, little information is available regarding the molecular mechanisms governing Ca-deficiency-triggered tipburn. This study comprehensively analysed the transcriptomic comparison between control and calcium treatments (CK and 0 mM Ca) in Chinese cabbage to determine its molecular mechanism in tipburn. Our analysis identified that the most enriched gene ontology (GO) categories are photosynthesis, thylakoid and cofactor binding. Moreover, the KEGG pathway was most enriched in photosynthesis, carbon metabolism and carbon fixation. We also analyzed the co-expression network by functional categories and identified ten critical hub differentially expressed genes (DEGs) in each gene regulatory network (GRN). These DEGs might involve abiotic stresses, developmental processes, cell wall metabolism, calcium distribution, transcription factors, plant hormone biosynthesis and signal transduction pathways. Under calcium deficiency, CNX1, calmodulin-binding proteins and CMLs family proteins were downregulated compared to CK. In addition, plant hormones such as GA, JA, BR, Auxin and ABA biosynthesis pathways genes were downregulated under calcium treatment. Likewise, HATs, ARLs and TCP transcription factors were reported as inactive under calcium deficiency, and potentially involved in the developmental process. This work explores the specific DEGs’ significantly different expression levels in 0 mM Ca and the control involved in plant hormones, cell wall developments, a light response such as chlorophylls and photosynthesis, transport metabolism and defence mechanism and redox. Our results provide critical evidence of the potential roles of the calcium signal transduction pathway and candidate genes governing Ca-deficiency-triggered tipburn in Chinese cabbage.

Chinese cabbage, which is a cold season crop, can still be damaged at an overly low temperature. It is crucial to study the mechanism of the resistance to low temperature of Chinese cabbage. In this study, the Chinese cabbage ‘XBJ’ was used as the material, and nine different low temperatures and control samples were treated. Using RNA-seq and lignin content determination, we analyzed 27 samples, and the stained sections of them were observed. A total of 8845 genes were screened for the WGCNA analysis, yielding 17 modules. The GO and KEGG analyses of the modules was highly associated with a low-temperature treatment. The pathways such as ‘starch and sucrose metabolism’ and ‘plant hormone signal transduction’ were enriched in modules related to low temperature. Interestingly, L-15DAT-associated MEcoral2 was found to have 14 genes related to the ‘lignin biosynthetic process’ in the GO annotation. The combination of the determination of the lignin content and the treatment of the stained sections showed that the lignin content of the low-temperatures samples were indeed higher than that of the control. We further explored the expression changes of the lignin synthesis pathway and various genes and found that low temperature affects the expression changes of most genes in the lignin synthesis pathway, leading to the speculation that the lignin changes at low temperature are a defense mechanism against low temperatures. The 29 BrCOMT gene sequence derived from the RNA-seq was non-conserved, and eight BrCOMT genes were differentially expressed. This study provides a new insight into how lignin is affected by low temperature.

With increasing nitrogen application in soil, the problem of nitrate accumulation in soil and vegetable bodies has become increasingly serious. In this study, Bacillus subtilis (B. subtilis) Strain11 was isolated and studied for its effects in combination with Molybdenum (Mo) on the growth of Chinese cabbage and soil nitrate content. The results showed that the strain effectively increased the growth, height, and moisture content of Chinese cabbage by 27% and 2.5%, respectively, compared to the control. Mo application alone reduced soil nitrate accumulation and increased root length, height, chlorophyll content, and moisture content of Chinese cabbage, with an optimal rate of 0.8–1.2 mg/kg soil. The application of Mo fertilizer in combination with the Bacillus strain was the most effective in increasing plant height and root length of Chinese cabbage, which were 1.49 times and 1.68 times that of the control, respectively. The proportion of dry matter, the average fresh weight, and the dry weight under this treatment were 9.01%, 5.83 g/plant, and 0.53 g/plant, respectively, higher than the rest. At harvest, the highest ammonium-nitrogen content in this treatment group was 8.56 mg/kg, and the soil nitrate reduction reached 40.68%. In conclusion, Mo fertilizer at a rate of 0.8 mg Mo/kg soil, in combination with B. subtilis Strain11, was recommended for the remediation of nitrate-contaminated soils.

Heat stress is one of the most common agrometeorological risks in crop production in the middle and lower reaches of the Yangtze River in China. This study aimed to investigate whether glutamic acid (Glu) or poly-γ-glutamic acid (γ-PGA) biostimulants can improve the thermotolerance of a cool-season Chinese cabbage (Brassica rapa L. ssp. pekinensis) crop. Priming with Glu (2.0 mM) or γ-PGA (20 mg·L−1) was conducted at the third leaf stage by applying as daily foliar sprays for 5 days before 5 days of heat stress (45 °C in 16-h light/35 °C in 8-h dark). Coupled with morpho-physiological and biochemical analyses, transcriptomes of Glu or γ-PGA-primed Chinese cabbage under heat stress were examined by RNA-seq analysis. The results showed that the thermotolerance conferred by Glu and γ-PGA priming was associated with the increased parameters of vegetative growth, gas exchange, and chlorophyll fluorescence. Compared with the control, the dry weights of plants treated with Glu and γ-PGA increased by 51.52% and 39.39%, respectively. Glu and γ-PGA application also significantly increased the contents of total chlorophyll by 42.21% and 23.12%, and carotenoid by 32.00% and 24.00%, respectively. In addition, Glu- and γ-PGA-primed plants markedly inhibited the levels of malondialdehyde, electrolyte leakage, and super-oxide anion radical, which was accompanied by enhanced activity levels of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD). Enrichment analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) categories within the differentially expressed genes (DEGs) functional clusters of RNA-seq data indicated that the expression levels of the genes for DNA replication, DNA repair system, linoleic acid metabolism, cysteine and methionine metabolism, glutathione metabolism, purine and pyrimidine metabolism, carotenoid biosynthesis, and plant–pathogen interaction were commonly up-regulated by both Glu and γ-PGA priming. Glu treatment enhanced the expression levels of the genes involved in aliphatic glucosinolate and 2-oxocarboxylic acid, while γ-PGA treatment activated carotenoid cleavage reaction to synthesize abscisic acid. Taken together, both Glu and γ-PGA have great potential for the preadaptation of Chinese cabbage seedlings to heat stress, with Glu being more effective than γ-PGA.

Circadian clocks integrate environmental cues with endogenous signals to coordinate physiological outputs. Clock genes in plants are involved in many physiological and developmental processes, such as photosynthesis, stomata opening, stem elongation, light signaling, and floral induction. Many Brassicaceae family plants, including Chinese cabbage (Brassica rapa ssp. pekinensis), produce a unique glucosinolate (GSL) secondary metabolite, which enhances plant protection, facilitates the design of functional foods, and has potential medical applications (e.g., as antidiabetic and anticancer agents). The levels of GSLs change diurnally, suggesting a connection to the circadian clock system. We investigated whether circadian clock genes affect the biosynthesis of GSLs in Brassica rapa using RNAi-mediated suppressed transgenic Brassica rapa GIGENTEA homolog (BrGI knockdown; hereafter GK1) Chinese cabbage. GIGANTEA plays an important role in the plant circadian clock system and is related to various developmental and metabolic processes. Using a validated GK1 transgenic line, we performed RNA sequencing and high-performance liquid chromatography analyses. The transcript levels of many GSL pathway genes were significantly altered in GK1 transgenic plants. In addition, GSL contents were substantially reduced in GK1 transgenic plants. We report that the BrGI circadian clock gene is required for the biosynthesis of GSLs in Chinese cabbage plants.

Successful Agrobacterium-mediated transformations of Chinese cabbage have been limited owing to the plant’s recalcitrant nature, genomic background and explant necrosis upon infection, which hinders the transfer of T-DNA region into the Chinese cabbage. Consequently, in the current experiment, a stable Agrobacterium tumefaciens-mediated transformation method for Chinese cabbage cv. Kenshin established by employing important anti-oxidants in the co-cultivation and subsequent regeneration media. Four-day-old in vitro derived cotyledon explants were infected with A. tumefaciens strain GV3101 harboring the vector pCAMIBA1303. Cotyledon explants exposed to an Agrobacterium suspension (OD600 of approximately 0.6) for 10 min and then incubated for 3 days co-cultivation in Murashige and Skoog medium containing an L-cysteine + AgNO3 combination exhibited the highest β-glucuronidase (GUS) expression (94%) and explant regeneration efficiency (76%). After 3 days, the cotyledon explants were subjected to three selection cycles with gradually increasing hygromycin B concentrations (10 to 12 mg/L). The incorporation and expression of hptII in T0 transformed plants were verified by polymerase chain reaction and Southern blot analyses. These transgenic plants (T0) were fertile and morphologically normal. Using the present protocol, a successful transformation efficiency of 14% was achieved, and this protocol can be applied for genome editing and functional studies to improve Chinese cabbage traits.

Leaves are the main organ for photosynthesis, and variations in leaf color affect photosynthesis and plant biomass formation. We created two similar whole-plant pale green mutants (pem1 and pem2) from the double haploid (DH) Chinese cabbage line “FT” through ethyl methanesulfonate (EMS) mutagenesis of seeds. Photosynthetic pigment contents and net photosynthetic rates were significantly lower in the mutants than in the wild-type “FT,” and the chloroplast thylakoid endomembrane system was poor. Genetic analysis showed that the mutated phenotypes of pem1 and pem2 were caused by a single nuclear gene. Allelism tests showed that pem1 and pem2 were alleles. We mapped Brpem1 to a 64.25 kb region on chromosome A10, using BSR-Seq and map-based cloning of 979 F2 recessive individuals. Whole-genome re-sequencing revealed a single nucleotide polymorphism (SNP) transition from guanine to adenosine on BraA10g021490.3C in pem1, causing an amino acid shift from glycine to glutamic acid (G to E); in addition, BraA10g021490.3C in pem2 was found to have a single nucleotide substitution from guanine to adenosine, causing an amino acid change from E to lysine (K). BraA10g021490.3C is a homolog of the Arabidopsisdivinyl chlorophyllide a 8-vinyl-reductase (DVR) gene that encodes 3,8-divinyl protochlorophyllide a 8-vinyl reductase, which is a key enzyme in chlorophyll biosynthesis. Enzyme activity assay and chlorophyll composition analysis demonstrated that impaired DVR had partial loss of function. These results provide a basis to understand chlorophyll metabolism and explore the mechanism of a pale green phenotype in Chinese cabbage.

We assessed the residual distribution and temporal trend of picarbutrazox sprayed by agricultural multicopters on Chinese cabbage and considered fortification levels and flying speeds. In plot 2, 14 days after the last spraying, the residues decreased by ~91.3% compared with those in the samples on day 0. The residues in the crops decreased by ~40.8% of the initial concentration owing to growth (dilution effect) and by ~50.6% after excluding the dilution effect. As the flight speed increased, picarbutrazox residues decreased (p < 0.05, least significant deviation [LSD]). At 2 m s−1 flight speed, the residual distribution differed from the dilution rate of the spraying solution. The average range of picarbutrazox residues at all sampling points was 0.007 to 0.486, below the limit of quantitation −0.395, 0.005–0.316, and 0.005–0.289 mg kg−1 in plots 1, 2, 3, and 4, respectively, showing significant differences (p < 0.05, LSD). These results indicated that the residual distribution of picarbutrazox sprayed by using a multicopter on the Chinese cabbages was not uniform. However, the residues were less than the maximum residue limit in all plots. Accordingly, picarbutrazox was considered to have a low risk to human health if it was sprayed on cabbage according to the recommended spraying conditions.

Salt is the most important limiting factor in plant yield and quality. Different Chinese cabbage cultivars appeared different salt tolerances, but there are few studies attempting to elucidate the mechanism underlying this phenomenon. In this study, 100 mmol L–1 NaCl was found to be the most suitable treatment concentration according to a sprouting bag test of 39 Chinese cabbage cultivars, and through comprehensive comparison and analysis, the relative values of fresh weight and electrolyte leakage in leaves proved to be convenient indicators for the identification of salt tolerance in Chinese cabbage. We analyzed the physiological responses of Qinghua45 (salt-tolerant) and Biyuchunhua (salt-sensitive) in terms of the growth indexes, ion homeostasis and Photosynthesis, the results indicated that Qinghua45 could ensure osmotic regulation, ion homeostasis and photosynthesis under salt stress. Next, we compared the transcriptome dynamics of the two cultivars. Overall, 2,859 differentially expressed genes (DEGs) were identified, and the number of DEGs in Qinghua45 was significantly less than that in Biyuchunhua. VDAC promoted the release of Ca2+, which indirectly promoted the transport of Na+ to vacuoles through the SOS2 pathway. Cation/H (+) antiporter 17 and V-H + -ATPase improve the exchange of Na+ and H+ and maintain Na+ in the vacuoles, thereby reducing the injury affected by salt stress. Increases in galactinol synthase and soluble protein synthesis helped relieve osmotic stress caused by salt, together, they regulated the Na+ content and chlorophyll biosynthesis of the plant and enabled the plant to adapt to salt stress over time.

Leaves are the main organ for photosynthesis, and variations in leaf color affect photosynthesis and plant biomass formation. We created two similar whole-plant pale green mutants (pem1 and pem2) from the double haploid (DH) Chinese cabbage line “FT” through ethyl methanesulfonate (EMS) mutagenesis of seeds. Photosynthetic pigment contents and net photosynthetic rates were significantly lower in the mutants than in the wild-type “FT,” and the chloroplast thylakoid endomembrane system was poor. Genetic analysis showed that the mutated phenotypes of pem1 and pem2 were caused by a single nuclear gene. Allelism tests showed that pem1 and pem2 were alleles. We mapped Brpem1 to a 64.25 kb region on chromosome A10, using BSR-Seq and map-based cloning of 979 F2 recessive individuals. Whole-genome re-sequencing revealed a single nucleotide polymorphism (SNP) transition from guanine to adenosine on BraA10g021490.3C in pem1, causing an amino acid shift from glycine to glutamic acid (G to E); in addition, BraA10g021490.3C in pem2 was found to have a single nucleotide substitution from guanine to adenosine, causing an amino acid change from E to lysine (K). BraA10g021490.3C is a homolog of the Arabidopsisdivinyl chlorophyllide a 8-vinyl-reductase (DVR) gene that encodes 3,8-divinyl protochlorophyllide a 8-vinyl reductase, which is a key enzyme in chlorophyll biosynthesis. Enzyme activity assay and chlorophyll composition analysis demonstrated that impaired DVR had partial loss of function. These results provide a basis to understand chlorophyll metabolism and explore the mechanism of a pale green phenotype in Chinese cabbage.

In this paper, we employ a combination of time regression discontinuity design method (T-RD) and the difference-in-difference method (DID) to identify and quantify the causal effects of the strict lockdown policy on vegetable prices using multiple-year daily price data from 151 wholesale markets of Chinese cabbage. We find that the lockdown policy caused a large and immediate surge in price and price dispersion of Chinese cabbage, though they fluctuated smoothly for the same period in normal years. The DID results further show that the price surge peaked in the fourth week of lockdown but gradually came down to the level of a normal year by week 11. However, the price rose again (though to a much smaller extent) in response to the resurgence of COVID-19 in a few provinces in early-mid April but quickly returned to the normal level in week 15 when the lockdown measures were largely removed. We also find that the supply chain disruption is the driving factor for the price hike. Policy implications are drawn.

Salt is the most important limiting factor in plant yield and quality. Different Chinese cabbage cultivars appeared different salt tolerances, but there are few studies attempting to elucidate the mechanism underlying this phenomenon. In this study, 100 mmol L–1 NaCl was found to be the most suitable treatment concentration according to a sprouting bag test of 39 Chinese cabbage cultivars, and through comprehensive comparison and analysis, the relative values of fresh weight and electrolyte leakage in leaves proved to be convenient indicators for the identification of salt tolerance in Chinese cabbage. We analyzed the physiological responses of Qinghua45 (salt-tolerant) and Biyuchunhua (salt-sensitive) in terms of the growth indexes, ion homeostasis and Photosynthesis, the results indicated that Qinghua45 could ensure osmotic regulation, ion homeostasis and photosynthesis under salt stress. Next, we compared the transcriptome dynamics of the two cultivars. Overall, 2,859 differentially expressed genes (DEGs) were identified, and the number of DEGs in Qinghua45 was significantly less than that in Biyuchunhua. VDAC promoted the release of Ca2+, which indirectly promoted the transport of Na+ to vacuoles through the SOS2 pathway. Cation/H (+) antiporter 17 and V-H + -ATPase improve the exchange of Na+ and H+ and maintain Na+ in the vacuoles, thereby reducing the injury affected by salt stress. Increases in galactinol synthase and soluble protein synthesis helped relieve osmotic stress caused by salt, together, they regulated the Na+ content and chlorophyll biosynthesis of the plant and enabled the plant to adapt to salt stress over time.

Chinese cabbage is a leafy vegetable, and its leaves are the main edible organs. The formation of trichomes on the leaves can significantly affect its taste, so studying this phenomenon is of great significance for improving the quality of Chinese cabbage. In this study, two varieties of Chinese cabbage, W30 with trichome leaves and 082 with glabrous leaves, were crossed to generate F1 and F1 plants, which were self-fertilized to develop segregating populations with trichome or glabrous morphotypes. The two bulks of the different segregating populations were used to conduct bulked segregant analysis (BSA). A total of 293.4 M clean reads were generated from the samples, and plants from the trichome leaves (AL) bulk and glabrous leaves (GL) bulk were identified. Between the two DNA pools generated from the trichome and glabrous plants, 55,048 SNPs and 272 indels were generated. In this study, three regions (on chromosomes 6, 10 and scaffold000100) were identified, and the annotation revealed three candidate genes that may participate in the formation of leaf trichomes. These findings suggest that the three genes—Bra025087 encoding a cyclin family protein, Bra035000 encoding an ATP-binding protein/kinase/protein kinase/protein serine/threonine kinase and Bra033370 encoding a WD-40 repeat family protein–influence the formation of trichomes by participating in trichome morphogenesis (GO: 0010090). These results demonstrate that BSA can be used to map genes associated with traits and provide new insights into the molecular mechanism of leafy trichome formation in Chinese cabbage.

Clubroot, caused by the soil-borne protist Plasmodiophora brassicae, is one of the most destructive diseases of Chinese cabbage worldwide. However, the clubroot resistance mechanisms remain unclear. In this study, in both clubroot-resistant (DH40R) and clubroot-susceptible (DH199S) Chinese cabbage lines, the primary (root hair infection) and secondary (cortical infection) infection stages started 2 and 5 days after inoculation (dai), respectively. With the extension of the infection time, cortical infection was blocked and complete P. brassica resistance was observed in DH40R, while disease scales of 1, 2, and 3 were observed at 8, 13, and 22 dai in DH199S. Transcriptome analysis at 0, 2, 5, 8, 13, and 22 dai identified 5,750 relative DEGs (rDEGs) between DH40R and DH199S. The results indicated that genes associated with auxin, PR, disease resistance proteins, oxidative stress, and WRKY and MYB transcription factors were involved in clubroot resistance regulation. In addition, weighted gene coexpression network analysis (WGCNA) identified three of the modules whose functions were highly associated with clubroot-resistant, including ten hub genes related to clubroot resistance (ARF2, EDR1, LOX4, NHL3, NHL13, NAC29, two AOP1, EARLI 1, and POD56). These results provide valuable information for better understanding the molecular regulatory mechanism of Chinese cabbage clubroot resistance.

Chinese cabbage is one of the most important and widely consumed vegetables in China. The developmental transition from the vegetative to reproductive phase is a crucial process in the life cycle of flowering plants. In spring-sown Chinese cabbage, late bolting is desirable over early bolting. In this study, we analyzed double haploid (DH) lines of late bolting (“Y410-1” and “SY2004”) heading Chinese cabbage (Brassica rapavar.pekinensis) and early-bolting Chinese cabbage (“CX14-1”) (B. rapassp.chinensisvar.parachinensis) by comparative transcriptome profiling using the Illumina RNA-seq platform. We assembled 721.49 million clean high-quality paired-end reads into 47,363 transcripts and 47,363 genes, including 3,144 novel unigenes. There were 12,932, 4,732, and 4,732 differentially expressed genes (DEGs) in pairwise comparisons of Y410-1 vs. CX14-1, SY2004 vs. CX14-1, and Y410-1 vs. SY2004, respectively. The RNA-seq results were confirmed by reverse transcription quantitative real-time PCR (RT-qPCR). A Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of DEGs revealed significant enrichment for plant hormone and signal transduction as well as starch and sucrose metabolism pathways. Among DEGs related to plant hormone and signal transduction, six unigenes encoding the indole-3-acetic acid-induced protein ARG7 (BraA02g009130), auxin-responsive protein SAUR41 (BraA09g058230), serine/threonine-protein kinase BSK11 (BraA07g032960), auxin-induced protein 15A (BraA10g019860), and abscisic acid receptor PYR1 (BraA08g012630 and BraA01g009450), were upregulated in both late bolting Chinese cabbage lines (Y410-1 and SY2004) and were identified as putative candidates for the trait. These results improve our understanding of the molecular mechanisms underlying flowering in Chinese cabbage and provide a foundation for studies of this key trait in related species.

Bolting is an important agronomic character of the Chinese cabbage, but premature bolting can greatly reduce its commercial value, yield, and quality. Here, early-bolting mutant 1 (ebm1) was obtained from a Chinese cabbage doubled haploid (DH) line “FT,” by using an isolated microspore culture and ethyl methanesulfonate (EMS) mutagenesis. The ebm1 was found to bolt extremely earlier than the wild type “FT.” Genetic analysis indicated that the phenotype of the ebm1 was controlled by a single recessive nuclear gene. Using a mapping population of 1,502 recessive homozygous F2 individuals with the ebm1 phenotype, the ebm1 gene was mapped to between the markers SSRhl-53 and SSRhl-61 on chromosome A04 by using SSR markers, and its physical distance was 73.4 kb. Seven genes were predicted in the target region and then cloned and sequenced; the only difference in the sequences of the ebm1 and “FT” genes was with Bra032169. Unlike that in “FT,” the Bra032169 in ebm1 had a novel 53 bp insertion that caused the termination of amino acid coding. The mutation was not consistent with EMS mutagenesis, and thus, may have been caused by spontaneous mutations during the microspore culture. Based on the gene annotation information, Bra032169 was found to encode the histone methyltransferase CURLY LEAF (CLF) in Arabidopsis thaliana. CLF regulates the expression of flowering-related genes. Further genotyping revealed that the early-bolting phenotype was fully co-segregated with the insertion mutation, suggesting that Bra032169 was the most likely candidate gene for ebm1. No significant differences were noted in the Bra032169 expression levels between the ebm1 and “FT.” However, the expression levels of the flowering-related genes FLC, FT, AG, and SEP3 were significantly higher in the ebm1 than in the “FT.” Thus, the mutation of Bra032169 is responsible for the early-bolting trait in Chinese cabbage. These results provide foundation information to help understand the molecular mechanisms of bolting in the Chinese cabbage.

In several regions in Europe, the amounts of both manure produced by pig husbandry and biogas digestates from anaerobic digestion are too high to be sustainably applied to the surrounding fields. In these regions, nutrient surpluses are therefore often a problem. The research projects GOBi and BioEcoSIM succeeded in developing innovative recycling technologies for the recovery of phosphorus (P) from biogas digestates and manure, converting them into valuable fertilizers. This study tested the suitability of recovered phosphate salts (“P-Salts”) and dried solids as P fertilizers for sunflower, marigold and Chinese cabbage in a greenhouse experiment. Treatments included two recovered P-Salts (from manure and digestate), two dried solids (air-dried and steam-dried), a combination of salt and solid, and triple superphosphate (TSP) as reference, each at two fertilization levels. Measurements included biomass production (ornamentals separated into shoots and flowers), P concentration in the biomass and plant-available P in the growing medium. Both P-Salts had more or less the same effect as TSP on biomass production. The combination of P-Salt and air-dried solids resulted in a synergistic effect on sunflower in terms of biomass yield, P concentration and number of flowers. The P concentration was mostly higher in plants treated at the higher P fertilizer level. A fast P uptake into plants and thus high plant availability is particularly important in the horticultural sector due to the short production periods of potted plants. In general, all the tested recycled products except the air-dried solids could be adapted to the requirements of different ornamentals, met their P demand as efficiently as TSP and thus have high potential as P fertilizers. The P-Salts are more suitable for short-term and the steam-dried solids more for long-term P supply. The combination of both may ensure optimal P supply and guarantee long-term product quality.

The arms race between plants and viruses never ceases. Chinese cabbage, an important type of Brassica vegetable crop, is vulnerable to plant virus infection, especially to Turnip mosaic virus (TuMV). To better examine the molecular mechanisms behind the virus infection, we conducted the correlation analysis of RNA-Seq and quantitative iTRAQ-LC-MS/MS in TuMV-infected and in healthy Chinese cabbage leaves. There were 757 differentially expressed genes and 75 differentially expressed proteins that were screened in Chinese cabbage plants infected with TuMV. These genes were enriched in many pathways, and among them, the plant hormone signal transduction, plant-pathogen interaction, and protein processing in the endoplasmic reticulum pathways were suggested to be closely related pathways. The correlation analysis between RNA-Seq and quantitative iTRAQ-LC-MS/MS was then further explored. Finally, we obtained a preliminary network of several candidate genes associated with TuMV infection, and we found that they mainly belonged to calcium signaling pathways, heat shock proteins, WRKY transcription factors, and non-specific lipid transfer proteins. These results may lead to a better understanding of antiviral mechanisms and of disease-resistant breeding.

In Chinese cabbage (Brassica rapa L. ssp. pekinensis), leaf adaxial-abaxial (ad-ab) polarity is tightly related to leaf incurvature, an essential factor for the formation of leafy heads. Therefore, identification of the genes responsible for leaf ad-ab polarity and studying their genetic variation may clarify the mechanism of leafy head formation. By comparing the sequences of the genes regulating leaf ad-ab polarity development in Arabidopsis thaliana (A. thaliana), 41 candidate genes distributed on 10 chromosomes were found to be responsible for the establishment of ad-ab polarity in Chinese cabbage. Orthologous genes, including 10 single copies, 14 double copies, and one triple copies, were detected in the Chinese cabbage. The gene structure and conserved domain analyses showed that the number of exons of the 41 candidate genes range from one to 25, and that most genes share the conserved motifs 1, 6, and 10. Based on the 41 candidate genes, 341 simple sequence repeats (SSRs) were detected, including five replicated types: single, double, triple, quintuple, and sextuple nucleotide replications. Among these sequence repeat (SSR) loci, 323 loci were used to design 969 specific primers, and 362 primer pairs were selected randomly and evaluated using 12 Chinese cabbage accessions with different heading types. 23 primer pairs resulting with clear, polymorphic bands, combined with other 127 markers, was used to construct a linkage map by using an F2 population containing 214 lines derived from the hybrid of the overlapping heading Chinese cabbage “14Q-141” and the outward curling heading Chinese cabbage “14Q-279.” The result showed that the sequences of markers in the genetic linkage map and the physical map was consistent in general. Our study could help to accelerate the breeding process of leafy head quality in Chinese cabbage.

In plants, calcineurin B-like proteins (CBL) are a unique set of calcium sensors that decode calcium signals by activating a plant-specific protein kinase family called CBL-interacting protein kinases (CIPKs). The CBL–CIPK family and its interacting complexes regulate plant responses to various environmental stimuli. Chinese cabbage (Brassica rapa ssp. pekinensis) is an important vegetable crop in Asia; however, there are no reports on the role of the CBLs–CIPKs’ signaling system in response to abiotic stress during cabbage growth. In this study, 18 CBL genes and 47 CIPK genes were identified from the Chinese cabbage genome. Expansion of the gene families was mainly due to tandem repeats and segmental duplication. An analysis of gene expression patterns showed that different duplicate genes exhibited different expression patterns in response to treatment with Mg2+, K+, and low temperature. In addition, differences in the structural domain sequences of NAF/FISL and interaction profiles in yeast two-hybrid assays suggested a functional divergence of the duplicate genes during the long-term evolution of Chinese cabbage, a result further validated by potassium deficiency treatment using trans-BraCIPK23.1/23.2/23.3 Arabidopsis thaliana. Our results provide a basis for studies related to the functional divergence of duplicate genes and in-depth studies of BraCBL–BraCIPK functions in Chinese cabbage.

Crop rotation can improve soil properties and is one of the important measures to prevent soil-borne diseases. This study aimed to evaluate the effects of different preceding crops on clubroot disease in Chinese cabbage and soil microorganisms, to provide a theoretical basis for the ecological control of clubroot scientifically. In this experiment, soybeans, potato onions, and wheat were used as the preceding crops and compared with the local preceding crop garlic. The growth of the Chinese cabbage, disease occurrence, soil chemical properties and changes in microbial community structure were determined by using quantitative real-time polymerase chain reaction (PCR), soil microbial high-throughput sequencing and other methods. The results showed that the rotation of potato onion and wheat with Chinese cabbage could reduce the clubroot disease index of Chinese cabbage remarkably. Through Illumina Miseq sequencing, when three previous crops were harvested, the abundance and diversity of the bacteria increased obviously, while the fungi decreased. The relative abundance of the phylum Proteobacteria and Firmicutes was strikingly reduced, while that of Chloroflexi was significantly increased. These results show that three previous crops changed the structure of soil microorganisms, reduced the clubroot disease of Chinese cabbage, promoted growth, and suppressed disease. The ranked effect on promoting growth and inhibiting diseases was potato onion > wheat > soybean.

Mutagenesis is an important tool for breeding and genomic research. In this study, the germinated seeds and isolated microspores of a double haploid line ‘FT’ were treated with EMS, respectively, with the aim of comparing the effects of the two approaches on generating mutants in Chinese cabbage. For microspore EMS mutagenesis, the isolated microspores were treated with 0.12% EMS for 20 min, a total of 1268 plantlets were obtained, and 15 M1 mutants were screened with a mutation frequency of 1.2%. For seed EMS mutagenesis, 7800 germinated seeds were treated with 0.8% EMS for 12 h, and a total of 701 M2 mutants were screened, with a mutation frequency of 18.78%. In total, 716 mutants with heritable morphological variation including leaf color, leaf shape, leafy head, bolting, and fertility, were obtained from the EMS mutagenesis experiments. Homozygous mutant plants could be screened from M1 lines by microspore mutagenesis, and M2 lines by seed mutagenesis. The mutation frequency was higher in seed mutagenesis than in microspore mutagenesis. Based on these results, we propose that seed EMS mutagenesis is more suitable to generate a large-scale mutant library, and the microspore EMS mutagenesis is conducive to rapidly obtaining homozygous mutants.

Selecting proper mechanical processing can improve performance of miscanthus substrates. We studied the effects of mechanical processing methods on substrate morphology, hydrological properties, pH, and nitrogen immobilization. Miscanthus × giganteus biomass was processed into field chips (FC, forage harvester), shreds (S5, mechanical fraying machine through a 5-mm screen) and chips (C15, C10, C5 and C3, hammermill with screen size of 15, 10, 5, or 3 mm). Processed miscanthus materials were also tested as propagation substrates for Chinese cabbage seedlings. Results showed that particle size distribution of miscanthus substrates formed four groups in ascending order of particle size: C3 < C5 < (C10, C15, S5) < FC. The finer miscanthus substrates had higher water holding capacity following the same groupings in particle size. The hydrophobicity of processed miscanthus was low and reversible, with the increasing order of risk as C3 < C5 < C10, C15 < S5, FC. All miscanthus substrates had similar and low pH buffering capacity. Nitrogen immobilization was similar among miscanthus substrates. The seedlings in miscanthus substrates had similar germination rates but a lower biomass compared to those grown in peat and coir. Primary mechanical modification of miscanthus offers opportunities for different sizes of substrate materials with few changes to the physical or chemical properties tested in this work.

Exploring ways to reduce the risk of heavy metal pollution by organic fertilizer application is of vital importance. In the present study, by conducting a pot experiment, natural zeolite was applied together with pig manure based organic fertilizer to agricultural soil in order to test its possibility of reducing the risk of heavy metals originating from pig manure. The results showed that a low rate of organic fertilizer (10%) application increased the biomass of Chinese cabbage (by 57.2%), while a high rate of organic fertilizer (30%) decreased the biomass of Chinese cabbage (by 46.16%), and meanwhile a 3% zeolite addition increased the biomass of Chinese cabbage which was treated with 30% organic fertilizer. The organic fertilizer addition decreased soil pH and increased soil CEC, while zeolite addition increased soil pH and decreased the soil organic matter content. The concentration of Zn in Chinese cabbage shoots increased with the organic fertilizer addition from 4.46% to 48.27%, while the addition of 1% and 3% zeolite significantly decreased Zn in Chinese cabbage shoots by 15.53% and 14.08%, respectively. The concentration of DPTA-extractable and DGT-extractable Zn of soil was increased by organic fertilizer application, whereas zeolite addition decreased the concentration of DPTA-extractable and DGT-extractable Zn in soil treated with organic fertilizer. Our present study suggests that natural zeolite application could be a promising method to reduce the risk of heavy metals originating from organic fertilizers.

Plants respond to herbivorous insect attacks by releasing volatiles that directly harm the herbivore or that indirectly harm the herbivore by attracting its natural enemies. Although the larvae of Spodoptera litura (the tobacco cutworm) are known to induce the release of host plant volatiles, the effects of such volatiles on host location by S. litura and by the parasitoid Microplitis similis, a natural enemy of S. litura larvae, are poorly understood. Here, we found that both the regurgitate of S. litura larvae and S. litura-infested cabbage leaves attracted M. similis. S. litura had a reduced preference for cabbage plants that had been infested with S. litura for 24 or 48 h. M. similis selection of plants was positively correlated with the release of limonene; linalool and hexadecane, and was negatively correlated with the release of (E)-2-hexenal and 1-Butene, 4-isothiocyanato. S. litura selection of plants was positively correlated with the release of (E)-2-hexenal, 1-Butene, 4-isothiocyanato, and decanal, and was negatively correlated with the release of limonene, nonanal, hexadecane, heptadecane, and octadecane. Our results indicate that host plant volatiles can regulate the behavior of S. litura and M. similis.

The present study aimed to investigate the contents of glucosinolates (GSLs) and carotenoids in eleven varieties of Chinese cabbage in relation to the expression level of the important transcription factors. MS and HPLC analysis identified the presence of 13 GSLs (progoitrin, sinigrin, glucoalyssin, gluconapoleiferin, gluconapin, glucocochlearin, glucobrassicanapin, glucoerucin, 4-hydroxyglucobrassicin, glucobrassicin, 4-methoxyglucobrassicin, neoglucobrassicin and gluconasturtiin) and four carotenoids (lutein, zeaxanthin, α-carotene and β-carotene). GSL contents were varied among the different cabbage varieties. The total GSL content ranged from 2.7 to 57.88μmol/gDW. The proportion of gluconapin (54%) and glucobrassicanapin (22%) was higher in all the varieties, respectively. Results documented the variation in total and individual carotenoid contents that have also been observed among different varieties; however, the total carotenoid contents ranged from 289.12 to 1001.41mgkg−1DW (mean 467.66). Interestingly, the proportion of lutein (66.5) and β-carotene (25.9) were higher than α-carotene (5.1) and zeaxanthin (2.5%). Consequently, the expression level of the regulatory gene, MYB28 was higher in ‘K0648’ and was directly proportional to GSL content. Similarly, the expression levels of 1-PSY were higher in ‘K0112’; however, the expression levels of 2-ZDS, 3-LCYB, 4-LCYE, 5-CHXB and 7-NCED genes showed no significant difference. In addition, the correlation between GSL and carotenoid contents and gene expression level showed moderate significant difference in each Chinese cabbage.

NH3 emitted into the atmosphere undergoes intricate chemical reactions to form fine particulate matter PM2.5. Nitrogen fertilizers are one of the major sources of gaseous ammonia. Recently, research into using biochar to lessen NH3 emissions from agricultural land has taken center stage and several studies have been executed in that regard. However, biochar’s capacity to reduce emissions of gaseous NH3 from applied nitrogen fertilizers is affected by both soil and biochar properties. While the effects of soil properties on NH3 volatilizations have been widely studied, the data concerning the effects of biochar properties on NH3 volatilizations from the soil are still scanty. It is against this backdrop that this study examined the effects of biochar pH on emissions of NH3 from the soil amended with varying quantities of nitrogen, as well as the impact on the growth and productivity of Chinese cabbage. To achieve the study objectives, acidic (pH 5.7), neutral (pH 6.7) and alkaline (pH 11.0) biochars were used and each was added to the soil at a rate of 1% (w/w). Nitrogen fertilizers were applied at three rates of 160, 320, 640 kg ha−1. In comparison with the control, the acidic, neutral and alkaline biochar amendments reduced NH3 emissions by up to 18%, 20% and 15%, respectively. However, only neutral biochar produced higher Chinese cabbage yields than the urea-only amendment and the Chinese cabbage yields increased with the increasing rates of nitrogen applied. Combined applications of neutral biochar and 640 kg/ha of nitrogen are recommended for optimal cabbage yields and low NH3 emissions.

Resistant and susceptible lines in Brassica rapa have different immune responses against Fusarium oxysporum inoculation. Fusarium yellows caused by Fusarium oxysporum f. sp. conglutinans (Foc) is an important disease of Brassicaceae; however, the mechanism of how host plants respond to Foc is still unknown. By comparing with and without Foc inoculation in both resistant and susceptible lines of Chinese cabbage (Brassica rapa var. pekinensis), we identified differentially expressed genes (DEGs) between the bulked inoculated (6, 12, 24, and 72 h after inoculation (HAI)) and non-inoculated samples. Most of the DEGs were up-regulated by Foc inoculation. Quantitative real-time RT-PCR showed that most up-regulated genes increased their expression levels from 24 HAI. An independent transcriptome analysis at 24 and 72 HAI was performed in resistant and susceptible lines. GO analysis using up-regulated genes at 24 HAI indicated that Foc inoculation activated systemic acquired resistance (SAR) in resistant lines and tryptophan biosynthetic process and responses to chitin and ethylene in susceptible lines. By contrast, GO analysis using up-regulated genes at 72 HAI showed the overrepresentation of some categories for the defense response in susceptible lines but not in the resistant lines. We also compared DEGs between B. rapa and Arabidopsis thaliana after F. oxysporum inoculation at the same time point, and identified genes related to defense response that were up-regulated in the resistant lines of Chinese cabbage and A. thaliana. Particular genes that changed expression levels overlapped between the two species, suggesting that they are candidates for genes involved in the resistance mechanisms against F. oxysporum.

14 páginas.- 2 figuras. 6 tablas.- referencias, In Portugal, many abandoned mines are often close to agricultural areas and might be used for plant food cultivation. Soils in the vicinity of two Mn- and Fe-abandoned mines (Ferragudo and Rosalgar, SW of Portugal) were collected to cultivate two different food species (Brassica rapa subsp. pekinensis (Lour.) Hanelt and Origanum vulgare L.). Chemical characterization of the soil–plant system and potential risk of adverse effects for human health posed by plants associated with soil contamination, based on the estimation of hazard quotient (HQ), were assessed in a microcosm assay under greenhouse conditions. In both soils, the average total concentrations of Fe and Mn were above the normal values for soils in the region and their concentration in shoots of both species was very high. Brassica rapa subsp. pekinensis grew better in Ferragudo than in Rosalgar soils, and it behaved as an excluder of Cu, Mn, Fe, S and Zn in both soils. The HQ for Cu, Fe, Mn and Zn in the studied species grown on both soils was lower than unit indicating that its consumption is safe. The high Mn tolerance found in both species might be due in part to the high contents of Fe in the soil available fraction that might contribute to an antagonism effect in the uptake and translocation of Mn. The obtained results emphasize the need of further studies with different food crops before cultivation in the studied soils to assess health risks associated with high metal intake.

Petal color, size, and morphology play important roles in protecting other floral organs, attracting pollinators, and facilitating sexual reproduction in plants. In a previous study, we obtained a petal degeneration mutant (pdm) from the ‘FT’ doubled haploid line of Chinese cabbage and found that the candidate gene for pdm, Bra040093, encodes the enzyme acyl-CoA oxidase1. In this study, we sought to examine the gene networks regulating petal development in pdm plants. We show that the mRNA and protein expression of Bra040093, which is involved in the jasmonic acid (JA) biosynthetic pathway, were significantly lower in the petals of pdm plants than in those of ‘FT’ plants. Similarly, the JA and methyl jasmonate (MeJA) contents of petals were significantly lower in pdm plants than in ‘FT’ plants and we found that exogenous application of these hormones to the inflorescences of pdm plants restored the ‘FT’ phenotype. Comparative analyses of the transcriptomes of ‘FT’, pdm and pdm + JA (pJA) plants revealed 10,160 differentially expressed genes (DEGs) with consistent expression tendencies in ‘FT’ vs. pdm and pJA vs. pdm comparisons. Among these DEGs, we identified 69 DEGs related to floral organ development, 11 of which are involved in petal development regulated by JA. On the basis of qRT-PCR verification, we propose regulatory pathways whereby JA may mediate petal development in the pdm mutant. We demonstrate that mutation of Bra040093 in pdm plants leads to reduced JA levels and that this in turn promotes changes in the expression of genes that are expressed in response to JA, ultimately resulting in petal degeneration. These findings thus indicate that JA is associated with petal development in Chinese cabbage. These results enhance our knowledge on the molecular mechanisms underlying petal development and lay the foundations for further elucidation of the mechanisms associated with floral organ development in Chinese cabbage.

Male sterility exists widely in flowering plants and is used as a fascinating tool by breeders for creating hybrid varieties. Herein, stamen samples from male sterile CCR20000 and male fertile CCR20001 lines during two developmental stages were employed to elucidate the molecular changes during flower development in fertile and sterile Chinese cabbage lines. RNA-seq revealed weak transcriptional activity in the sterile line, which may have led to the abnormal stamen development. The differentially expressed genes were enriched in plant hormone, carbon metabolism, and biosynthesis of amino acid pathways. Important genes with opposite patterns of regulation between the two lines have been associated with the male sterility trait. Members of the transcription factor families such as AP2, MYB, bHLH, and WRKY were highly active in the regulation of structural genes involved in pollen fertility. This study generated important genomic information to support the exploitation of the male sterility trait in Chinese cabbage breeding programs.

To analyze genetic linkage and map purple gene ( BrPur ) controlling purple inner leaves trait of Chinese cabbage, a F 2 population was constructed by selfing a F 1 plant from homozygous purple heading line ‘14S839’ and homozygous orange heading line ‘14S162’. The phenotype investigation of head color showed that the segregation ratio of purple to non-purple individuals was consistent with the expected ratio of 3:1, which indicated that purple inner leaves trait is controlled by a single dominant gene. A total of 297 SSRs in whole genome of Chinese cabbage were tested by modified Bulked Segregant Analysis (BSA) method. Two linked markers flanking BrPur , A710 and A714, were obtained and BrPur was mapped on linkage group A07 based on the sequence of these two markers. Subsequently, two new markers flanking BrPur , CL-12 and B214-87, were developed based on two known anthocyanins-related genes, Br4CL3 and Bra004214 . Genetic mapping of all markers in the F 2 mapping population showed CL-12 and B214-87 linked to BrPur with the genetic distance of 3.1 cM and 3.5 cM, respectively.

Clubroot disease caused by Plasmodiophora brassicae is one of the most serious diseases in Brassica crops worldwide. In this study, the pathotypes of 12 Korean P. brassicae field isolates were determined using various Chinese cabbage including 22 commercial cultivars from Korea, China, and Japan, and 15 inbred lines. All P. brassicae isolates exhibited the typical clubroot disease on non-clubroot resistant cultivar, indicating that the isolates were highly pathogenic. According to the reactions on the Williams’ hosts, the 12 field isolates were initially classified into five races. However, when these isolates were inoculated onto clubroot-resistant (CR) cultivars of Chinese cabbage, several isolates led to different disease responses even though the isolates have been assigned to the same race by the Williams’ host responses. Based on the pathogenicity results, the 12 field isolates were reclassified into four different groups: pathotype 1 (GN1, GN2, GS, JS, and HS), 2 (DJ and KS), 3 (HN1, PC, and YC), and 4 (HN2 and SS). In addition, the CR cultivars from Korea, China, and Japan exhibited distinguishable disease responses to the P. brassicae isolates, suggesting that the 22 cultivars used in this study, including the non-CR cultivars, are classified into four different host groups based on their disease resistance. Combining these findings, the four differential hosts of Chinese cabbage and four pathotype groups of P. brassicae might provide an efficient screening system for resistant cultivars and a new foundation of breeding strategies for CR Chinese cabbage.

Auxins play a pivotal role in clubroot development caused by the obligate biotroph Plasmodiophora brassicae. In this study, we investigated the pattern of expression of 23 genes related to auxin biosynthesis, reception, and transport in Chinese cabbage (Brassica rapa) after inoculation with P. brassicae. The predicted proteins identified, based on the 23 selected auxin-related genes, were from protein kinase, receptor kinase, auxin responsive, auxin efflux carrier, transcriptional regulator, and the auxin-repressed protein family. These proteins differed in amino acids residue, molecular weights, isoelectric points, chromosomal location, and subcellular localization. Leaf and root tissues showed dynamic and organ-specific variation in expression of auxin-related genes. The BrGH3.3 gene, involved in auxin signaling, exhibited 84.4-fold increase in expression in root tissues compared to leaf tissues as an average of all samples. This gene accounted for 4.8-, 2.6-, and 5.1-fold higher expression at 3, 14, and 28 days post inoculation (dpi) in the inoculated root tissues compared to mock-treated roots. BrNIT1, an auxin signaling gene, and BrPIN1, an auxin transporter, were remarkably induced during both cortex infection at 14 dpi and gall formation at 28 dpi. BrDCK1, an auxin receptor, was upregulated during cortex infection at 14 dpi. The BrLAX1 gene, associated with root hair development, was induced at 1 dpi in infected roots, indicating its importance in primary infection. More interestingly, a significantly higher expression of BrARP1, an auxin-repressed gene, at both the primary and secondary phases of infection indicated a dynamic response of the host plant towards its resistance against P. brassicae. The results of this study improve our current understanding of the role of auxin-related genes in clubroot disease development.

Background Plasmodiophora brassicae is a soil-borne plant pathogen that causes clubroot disease, which results in crop yield loss in cultivated Brassica species. Here, we investigated whether a quantitative trait locus (QTL) in B. rapa might confer resistance to a Korean P. brassicae pathotype isolate, Seosan. We crossed resistant and susceptible parental lines and analyzed the segregation pattern in a F2 population of 348 lines. We identified and mapped a novel clubroot resistance QTL using the same mapping population that included susceptible Chinese cabbage and resistant turnip lines. Forty-five resistant and 45 susceptible F2 lines along with their parental lines were used for double digest restriction site-associated DNA sequencing (ddRAD-seq). High resolution melting (HRM)-based validation of SNP positions was conducted to confirm the novel locus. Results A 3:1 ratio was observed for resistant: susceptible genotypes, which is in accordance with Mendelian segregation. ddRAD-seq identified a new locus, CRs, on chromosome A08 that was different from the clubroot resistance (CR) locus, Crr1. HRM analysis validated SNP positions and constricted CRs region. Four out of seventeen single nucleotide polymorphisms (SNPs) positions were within a 0.8-Mb region that included three NBS-LRR candidate genes but not Crr1. Conclusion The newly identified CRs locus is a novel clubroot resistance locus, as the cultivar Akimeki bears the previously known Crr1 locus but remains susceptible to the Seosan isolate. These results could be exploited to develop molecular markers to detect Seosan-resistant genotypes and develop resistant Chinese cabbage cultivars. Electronic supplementary material The online version of this article (10.1186/s12870-018-1615-8) contains supplementary material, which is available to authorized users.

Selected cultivars of Asian brassicacean vegetables were evaluated for their yield potential and susceptibility to bacterial infection. Chinese broccoli, two cultivars of Chinese cabbage (‘Dwarf milk cabbage’ and improved ‘Tahtsai’), and mizuna were grown in the conditions of the Czech Republic. Morphological and yield parameters for the field conditions (plant height, plant diameter, and marketable weight) were verified. In addition, genotypes were tested for resistance to black rot [Xanthomonas campestris pv. campestris (Xcc)] at the planting stage. The results show that a very promising genotype of mizuna, which yielded best (1,478 g per plant). Chinese cabbage (cultivar ‘Dwarf milk cabbage’) also showed high yield values (2,839 g per plant), especially when compared to the reference value for Napa cabbage. Chinese Cabbage 1 (‘Dwarf milk cabbage’) and mizuna also showed a low susceptibility to infection by bacterial black rot at the planting stage. Both cultivars reached Level 2 (median) of infection, which corresponds to the extent of the symptoms on 25% of the leaf surface.