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Abstract Potato black scurf caused by Rhizoctonia solani Kühn is widespread worldwide. The exploration and analysis of the infection mechanism of Rhizoctonia solani Kühn has important scientific significance to enhance the disease resistance of potato and other horticultural crops, and then break the restriction of fungal harm to agricultural production. The physiological and biochemical indexes and the expression levels of related genes were measured at 0, 1, 4, 8 and 16 days (T0, T1, T2, T3, T4) after inoculation with pathogenic bacteria. The results showed that the contents of L-phenylalanine ammonia-lyase (PAL), peroxidase (POD), lignin, total phenols (TP), and flavonoids increased significantly in potato after infection by Rhizoctonia solani Kühn, with the contents of PAL and POD reaching a peak at 8 d and then decreasing, and the contents of lignin and total phenols changing most significantly, reaching the highest levels at day 8 (T3) and day 16 (T4), respectively. During the infestation, the content of eight phenolic compounds increased, and the genes responsible for the lignin synthesis pathway were upregulated. However, in the later stage of infestation, the expression of two genes (PAL PG0031457 and PG2021549, HCT PG0014959, and COMT PG0011266) was down-regulated. In the correlation analysis, gene expression levels of all the genes, except POD (PG0005062), CCoAOMT (PG0018688), and COMT (PG0011266), were found to be positively correlated with the contents of lignin, total phenols, flavonoids, PAL, POD, and eight phenolic substances. Therefore, based on a sound understanding of the occurrence mechanism of Potato black scurf, this experiment analyzed the effect of Rhizoctonia solani Kühn infestation on the content of relevant metabolites in the lignin synthesis pathway as well as gene expression in potatoes, which provides a scientific basis for the prevention and control management of potato black scurf. Graphical Abstract

Abstract Background Heat and drought stresses usually occur together in nature, and both are expected to increase in frequency and intensity as a result of climate change. The synergistic impacts of these compound climate extremes on potatoes are far from the effects of individual stresses. However, the dynamics of the effects of combined heat and drought stresses on potato physiology and biochemistry have yet to be thoroughly assessed. To elucidate this point, we set up a pot experiment using ‘Atlantic’ potato seedlings as test material. A total of six treatments were set up: CK (normal growth conditions: 21 ℃, 0 PEG), A1B1 (31 ℃, 20% PEG), A1B2 (31 ℃, 10% PEG), A1B3 (31 ℃, 0 PEG), A2B1 (21 ℃, 20% PEG), and A2B2 (21 ℃, 10% PEG), and 15 physiological indices were determined with the stress time of 0, 6, 12 and 18 days. Results After 18 days of stress, the phenotype of potato seedlings was significantly different. Compared with CK, the thickness of potato leaves and palisade tissue increased under heat and drought stress, and the combined stress reduced the photosynthetic efficiency of potato leaves. In all treatments except CK, the chlorophyll content decreased significantly, the antioxidant enzyme activity increased first and then decreased, and the relative conductivity and malondialdehyde content increased significantly. The heat and combined treatment made the content of the osmotic regulator first increase and then decrease, while the treatment of 21 ℃ had no significant change. According to the correlation, principal component and interaction analysis, both heat and drought treatment had significant effects on each index, and the longer the stress time, the greater the effect, and the effect of combined stress was greater than that of single stress. However, after 6 days of stress, the activity of antioxidant enzymes and the content of transparent regulatory substances increased. Conclusions In conclusion, potato can cope with heat, drought and combined stress by adjusting leaf tissue structure, antioxidant enzyme activity and osmotic regulatory substances in a short time. Graphical Abstract

Abstract Background Potato (Solanum tuberosum L.) production is seriously threatened by the oomycete Phytophthora infestans (P. infestans). However, it remains unclear how the two potato cultivars, Q9 (moderately resistant) and Atl (susceptible), initiate distinct defense responses after inoculation with P. infestans. To uncover the underlying process, we investigated the dynamic gene expression profiles and the functions of the differentially expressed genes (DEGs). Results The results showed that the numbers of up-regulated DEGs were 1345, 1063 and 1694 in Q9 and 272, 603 and 2554 in Atl at 1 day post inoculation (dpi), 3 dpi and 5 dpi, respectively. Meanwhile, the down-regulated DEGs were 1557, 1417 and 389 in Q9 and 114, 364 and 2528 in Atl simultaneously. KEGG enrichment analysis revealed that plant-pathogen interaction, phenylpropanoid biosynthesis and MAPK signaling pathway were significantly enriched in Q9 at the later stage. Furthermore, DEGs associated with plant-pathogen interaction and phenylpropanoid biosynthesis showed higher expression levels in Q9 compared to Atl, especially at the later stage. The expressions of eight DEGs were validated by quantitative real-time PCR (qRT-PCR), which further verified the accuracy of the transcriptomics analysis. In addition, DEGs that were exclusively up-regulated and down-regulated in Q9 were analyzed, which may contribute to the resistance of Q9. Transient expression analysis revealed that four DEGs, including StHP1, StMYB2, StHSP3 and StNAC5, exhibited increased tolerance to P. infestans, indicating a positive role in enhancing the resistance of Q9. Conclusion Therefore, the DEGs associated with plant-pathogen interaction, phenylpropanoid biosynthesis and MAPK signaling pathway were involved in regulating late blight, and the expression level of the related genes significantly increased in Q9. In addition, StHP1, StHSP3 and the transcription factors, including StMYB2 and StNAC5, played positive roles in improving the resistance of potato Q9 to P. infestans. These findings provide useful information for further understanding the molecular mechanism of potato resistance to late blight. Furthermore, our study identified novel resistance genes that can be used in resistance breeding and functional research. Graphical abstract

Abstract Background GAox is a key enzyme involved in GA biosynthesis pathway and plays an important role in regulating various processes in plant life cycle. However, it has not been systematic, studies have been conducted in potato, which is the world's fourth largest food crop. Methods In this work, we systematically identified GAox gene family (StGAox) in potato by analyzing the potato genome sequence using a set of bioinformatics approaches, and analyze their physical, chemical properties, distribution on chromosomes, gene structure, conserved motifs, gene duplication events and expression patterns were analyzed. Results The results showed that a total of 33 GAox proteins were identified and unevenly distributed on 10 chromosomes. Based on their protein structure and phylogenetic characteristics, these 33 StGAoxes were divided into 5 distinct subclasses. Collinearity analysis revealed that there were 5 pairs of duplicated genes in the StGAox gene family, and all of which evolved under purifying selection. Analysis of RNA-seq data of double haploid (DM) potatoes under different tissues, abiotic stresses and hormone treatments showed that PG0002068, PG0024249 and PG0027963 were higher expressed in leaves, PG009427, PG0026762, PG0009021 and PG0021095 were higher expressed in tubers, PG2003479, PG0024249, PG0005698, and PG0009021were higher expressed in shoots than those of other tissues. In addition, the expression of PG0002068, PG2003479, PG0032156, PG0024249, and PG0021292 were up-regulated under mannitol and drought stress. Conclusions Comparative genome-wide analysis of StGAox genes and their expression analyses revealed that members of this family may be involved in tissue-specific developmental and abiotic stress responses. Graphical Abstract

Abstract Background With the rapid development of the economy and society, soil pollution is becoming more and more serious. Heavy metal cadmium (Cd) pollution is one of the typical problems, which poses a potentially serious threat to crop production and human health. Cinnamyl alcohol dehydrogenase (CAD) is a key enzyme in lignin synthesis and plays an important role in plant resistance to external stress. In this study, combined with bioinformatics analysis and expression pattern analysis, the members of the potato CAD family were identified, and their physical and chemical properties, evolutionary characteristics and chromosome location were clarified, as well as their regulatory effects on Cd tolerance. Results A total of 50 StCAD genes belonging to 6 subfamilies were obtained, and all of them were located in the cytoplasm. Members of the same family had similar gene structures and functional domains. The promoter region of each StCAD family member contains at least 5 or more abiotic stress response elements, indicating that the family had potential functions in regulating stress. According to the expression pattern analysis, most genes in this family were upregulated after Cd stress, further enhanced CAD activity and significantly promoted lignin accumulation in potato roots. Conclusion In summary, the StCAD family plays an important role in potato response to Cd stress. This study lays a foundation for further studies on the functions of the StCAD family and provides candidate genes for Cd resistance molecular breeding in potato. Graphical Abstract

Abstract Background Continuous cropping can reduce soil quality and affect rhizosphere metabolism, ultimately reducing crop yield. Crop rotation can mitigate the damage caused by continuous cropping, but different crop rotation patterns respond differently to soil quality and rhizosphere metabolism. We investigated the effects of different cropping patterns on soil physicochemical properties, enzyme activities, microbial quantity, and rhizosphere metabolism of continuous potato cropping based on a long-term field study from 2018 to 2022. The experiment was set up with the following three treatments: potato (Solanum tuberosum L.)-potato-potato-potato-potato (CK), potato-potato-potato-pea (Pisum arvense L.)-potato (T1), and potato-potato-potato-faba bean (Vicia faba L.)-potato (T2). Results The results showed that pea-potato rotation (T1) and faba bean-potato rotation (T2) significantly improved soil physicochemical properties and microbial quantity, enhanced enzyme activity, and increased yield by 21.19% and 28.38%, respectively, compared with the continuous potato crop. Non-targeted metabolomics analysis showed that the differential metabolites of pea-potato and faba bean-potato rotation were mainly nucleotides, organic acids and derivatives, and flavonoids compared to continuous potato cropping. These differential metabolites are mainly enriched in the ABC transporter, purine metabolism, pyrimidine metabolism, and phenylalanine metabolism pathways. Combined analyses showed that legume-potato rotations improved soil physicochemical properties, enzyme activities, and microbial quantity of continuous potato cropping, ultimately increasing tuber yields. In addition, correlation analyses showed that differential metabolites significantly enriched in purine and phenylalanine metabolism (l-Tyrosine, Trans-Cinnamic acid, Guanine, and Adenine) were also strongly associated with these measurements. Conclusions Therefore, we conclude that legume-potato rotations modulate the abundance and function of rhizosphere metabolites and significantly alter the low molecular metabolite profile of the soil under continuous potato conditions. Some of these important metabolites may play a part in the cycling of nutrients in the soil, making its physicochemical properties and microbial quantity better, raising the activity of soil enzymes, and ultimately increasing the yield of potato tubers. The above results indicate that legume-potato rotation has a positive effect on continuous potato soils. It lays a solid foundation for revealing the complex molecular network and metabolic pathways of microbial communities in soil after legume crop rotation. Graphical Abstract

Abstract Background Potato (Solanum tuberosum L.) continuous cropping causes the decrease of tuber yield, deterioration of quality and soil degradation in the semi-arid area. These negative effects can generally be mitigated by legume rotation and mulching. However, little is known about how can mulching and legume rotation alleviate the above damage through altering soil environment. Methods A field experiment was conducted to investigate changes in soil properties and microbial community in response to legume rotation and mulching under six planting patterns: potato continuous cropping without film mulching (PC), potato continuous cropping with film mulching (PCF), potato–broad bean rotation without film mulching (R1), potato–broad bean rotation with film mulching (R1F), potato–pea rotation without film mulching (R2) and potato–pea rotation with film mulching (R2F). Results Compared with the PC, the R1F and R2F had significantly enhanced the contents of alkaline nitrogen (AN), available phosphorus (AP), available potassium (AK), total carbon (TC) and total nitrogen (TN), but reduced soil pH and electrical conductivity (EC). The Shannon index of fungi in R1F and R2 was significantly higher than other treatments. The dominant bacterial and fungal phyla of each treatment was Proteobacteria and Ascomycota. R1, R1F, R2 and R2F enhanced the relative abundance of metabolic fungi and altered key differential microbial species. Soil EC, AN and AK were major factors influencing the soil bacterial and fungal communities. Conclusion Overall, the study demonstrated that potato-broad bean/pea rotation with mulching can be adopted as the preferred cropping systems to alleviate potato continuous cropping obstacles through enhancing soil fertility and regulating soil microbial communities in the semi-arid of Loess Plateau, China. Graphical Abstract

Highlights 1. Glutathione affected the synthesis of phenylpropanoid in the potato. 2. Glutathione affected the levels of plant hormone and the expression of related genes in potato. 3. Glutathione enhanced the tolerance of potato to cadmium stress. 4. Some genes play an important role in potato response to cadmium stress.

Abstract Background The potato (Solanum tuberosum L.) is an important food crop in the alkaline soil area of northwest China. It is abundant in ascorbic acid (vitamin C), which facilitates iron absorption in the body. The large consumption of potato makes it a good food source of iron absorption for human body. However, iron deficiency in alkaline soil regions reduced chlorophyll synthesis in the leaves, resulting in lower photosynthesis and less sugar supply to the plant's healthy organs, significantly restricted crop development and yield, and inflicted major economic losses. Methods In this study, a 2-year (2020–2021) field trial was designed. Under foliar application of five different iron fertilizers: ferric sulfate [(Fe2(SO4)3], T1; ferrous sulfate (FeSO4·7H2O), T2; citric acid/ferric sulfate (CA/Fe2(SO4)3), T3; citric acid/ferrous sulfate (CA/FeSO4·7H2O), T4; ethylenediamine tetra acetic acid (EDTA-Fe·Na), T5, changes in potato plant photosynthesis were compared to no iron fertilization, CK conditions. The effects of various iron fertilizers on the yield, quality, and iron content of potato tubers, their correlations to chlorophyll levels, and the characteristics of photosynthetic fluorescence were studied. Results The results indicated that spraying iron fertilizers increased the yield, quality and Fe content of the tubers, which might be due to the improvement of the plants’ photosynthetic pigment content, gas exchange parameters and chlorophyll fluorescence. In two consecutive years of cultivation, we found that potato tuber yield and Fe content increased in potatoes treated with five iron fertilizer sprays. Among them, tuber yield increased most significantly by T5 and T3 treatments compared to CK, while Fe content was significantly higher by the T5 treatment than by CK and other treatments. Tuber yield was increased by 33.28% and 18.85% in 2020 and 50.74% and 54.48% in 2021 by T5 and T3 treatments, respectively, compared to CK. Fe content was increased by 112.64% and 54.98% in 2020 and 2021 by T5 treatment, respectively, compared to CK. Conclusions EDTA-Fe·Na and CA/Fe2(SO4)3 excelled over the other iron fertilizers. The findings of this study are instructive for developing cost-effective iron fertilizer management systems to maximize the impact of iron biofortification on human health. Graphical Abstract

Abstract Background The growth of potato (Solanum tuberosum L.) is severely affected by the complex and variable soil environment, and film mulching has been widely used for potato growth in semiarid areas of western China. However, there are few studies on the effects of film mulching on soil quality and tuber yield in potato fields. Methods The effects of four mulching patterns (flat plot without film mulching, FP; flat plot with film mulching, FPM; ridge planting with half mulch, RPHM; ridge planting with full mulch, RPFM) on soil chemical and biological properties and potato tuber yield were investigated during two growing seasons (2018 and 2019) in the field. Results The results showed that compared with FP, the mulching treatments significantly increased the tuber yield of potato, with an increase of 3.7–20.77% and 7.89–26.35% in 2018 and 2019, respectively, and the yield of RPFM was higher than that of other treatments. In both growing seasons, RPFM significantly increased the contents of alkali-hydrolyzed N and available P, and the activities of soil urease, catalase, alkaline phosphatase, and sucrase. Bacterial and actinomycete counts were significantly higher in RPFM than those in the other treatments. Furthermore, RPFM significantly increased large potatoes and decreased small potatoes. Pearson’s correlation analysis revealed that soil alkaline dissolved nitrogen and actinomycete populations were the main factors affecting potato yield formation. Conclusions These results indicate that RPFM can improve the soil environment and further increase potato tuber yield, which is a viable option for potato production in semiarid areas. Graphical Abstract