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Efforts to maintain rice production in the future face many challenges, including the availability of increasingly narrow land, attacks by plant pest organisms, and declining land fertility due to improper cultivation systems. More than 70% of rice fields are in a disturbed ecological status due to cultivation technology that could be more environmentally friendly, which can interfere with the sustainability of rice self-sufficiency. An environmentally friendly rice cultivation system needs to be developed. This study aims to measure the agronomic and physiological responses of 3 rice genotypes in sustainable cultivation systems. The experiment used a Group Random Design on 3 rice genotypes (black, red, and white) in both conventional and sustainable cultivation systems. The research was carried out in the experimental garden of Polinela Organic Farm, Lampung State Polytechnic, from September 2020 to September 2021. The results showed that the plant, leaf greenery, number of tillers, number of panicles, grain weight per panicle, and biomass weight were not significantly different between conventional and sustainable cultivation. At the same time, the harvest and production indices per hectare were significantly different. The physiological responses to the photosynthesis and transpiration rates differed markedly in conventional and continuous cultivation. In contrast, the conductance of stomata did not differ significantly in both cultivation systems. The red rice genotype is the best, and it has a broader adaptation to conventional and sustainable cultivation systems. [ABSTRACT FROM AUTHOR]

Extended Abstract Introduction and Objective: Grain quality is one of the most important goals of rice breeding. One of the important traits in rice grain quality is its aroma, which is the result of the expression of recessive mutations of the OsBadh2 gene and determines the economic value of rice. In this research, the phenotypic and molecular screening of 50 different genotypes of rice was done based on the markers related to the aroma trait. Materials and Methods: In this research, 50 local and improved genotypes of rice were prepared from the collection of the Rice Research Institute of Iran, and the aroma trait was based on biochemical evaluation related to phenotypic selection based on the intensity of the aroma created in the treatment with 1.7 potassium hydroxide solution percentage and genotypic selection were done based on the band pattern created from the amplified gene sequence by using 3 pairs of specific primers (Badh2, Badex7-5 and Nksbad2) contiguous with the gene locations controlling the scent trait. To analyze the correlation between genes and the observed phenotype, the generalized linear logistic regression model was used. Results: Based on phenotypic evaluation, 31 aromatic cultivars and 19 non-aromatic cultivars were identified, which were in full agreement with the data obtained from genotypic screening, and it was found that Badh2 and Nkshad2 markers are able to predict and distinguish aromatic and non-aromatic cultivars with high confidence and accuracy. Conclusion: Badh2 and Nksbad2 markers can be used as efficient markers in genetic localization of diverging populations for fragrance as a Codominant marker instead of a phenotypic evaluation method.

Introduction and Objective: Grain quality is one of the most important goals of rice breeding. One of the important traits in rice grain quality is its aroma, which is the result of the expression of recessive mutations of the OsBadh2 gene and determines the economic value of rice. In this research, the phenotypic and molecular screening of 50 different genotypes of rice was done based on the markers related to the aroma trait. Materials and Methods: In this research, 50 local and improved genotypes of rice were prepared from the collection of the Rice Research Institute of Iran, and the aroma trait was based on biochemical evaluation related to phenotypic selection based on the intensity of the aroma created in the treatment with 1.7 potassium hydroxide solution percentage and genotypic selection were done based on the band pattern created from the amplified gene sequence by using 3 pairs of specific primers (Badh2, Badex7-5 and Nksbad2) contiguous with the gene locations controlling the scent trait. To analyze the correlation between genes and the observed phenotype, the generalized linear logistic regression model was used. Results: Based on phenotypic evaluation, 31 aromatic cultivars and 19 non-aromatic cultivars were identified, which were in full agreement with the data obtained from genotypic screening, and it was found that Badh2 and Nkshad2 markers are able to predict and distinguish aromatic and non-aromatic cultivars with high confidence and accuracy. Conclusion: Badh2 and Nksbad2 markers can be used as efficient markers in genetic localization of diverging populations for fragrance as a Codominant marker instead of a phenotypic evaluation method. [ABSTRACT FROM AUTHOR]

The rhizosphere microbiome plays a vital role in crop growth and adaptation. However, the effects of rice genotype, nitrogen (N) fertilization, and their interactions on the rhizosphere bacterial communities in low fertility soil remain poorly understood. In this study, a two-factor field experiment was performed in newly reclaimed mudflat paddies characterized by poor fertility to analyze bacterial communities in the rhizosphere of Yongyou 2640 (japonica/indica hybrid rice, JIH) and Huaidao No.5 (japonica conventional rice, JC) under different N fertilizer rates. Results showed that genotype, followed by N fertilizer rate, was the primary factor affecting rhizobacteria diversity. Rhizobacteria diversity was higher in JIH than in JC and that of JIH and JC did not significantly change overall as N fertilizer rates but increased and decreased at N fertilizer rates of over 300 kg N ha−1, respectively. The inconsistent response was probably attributed to the difference in the increase of ammonium and/or nitrate in the rhizosphere of JIH and JC. Genotype explained approximately 26% of the variation in rhizosphere bacterial communities. Rhizosphere bacterial communities with N fertilizer rates of over 300 kg N ha−1 were more dissimilar to those without N fertilization relative to those with N fertilizer rates of below 300 kg N ha−1, which was mainly attributed to changes in the concentration of ammonium and/or nitrate. The relative abundances of some potential beneficial genera such as Salinimicrobium, Salegentibacter, Gillisia, and Anaerolinea in the rhizosphere of JC and Salegentibacter, Lysobacter, Nocardioides, and Pontibacter in the rhizosphere of JIH were increased under N fertilizer rates of less than 300 kg N ha−1 and positively correlated with rice yields, which indicate that changes in bacterial communities caused by N fertilization might be strongly associated with the improvement of rice yield. Overall, rhizosphere bacterial communities were more sensitive to genotype in newly reclaimed mudflat paddies and showed a consistent response to N fertilizer rates. [ABSTRACT FROM AUTHOR]

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To mitigate the impact of extreme weather incidents, rice cultivars Way Seputih (WS) and Way Apo Buru (WAB) were evaluated under simulation of continuous wind and rainfall treatments. The research was conducted from July to October 2017 at Leuwikopo Experimental Farm, Bogor, Indonesia. For 15 days at day time, flowering rice hills were treated with about 100 mm/h water shower (Experiment-1), and with 0, 10-15, 20-25 and 35-40 km/h wind velocity (Experiment-2). Results showed that wind and rainfall treatments reduced rice production; the effect depended on the genotypes and flowering stage. Rain treatment from panicle emergence to 50%-emerged increased the number of unfilled grains by 154.6-182.3% and 55.7-101.9% in WS and WAB cultivars, respectively. Rain treatment at 100%-emerged had no effect on WS, but it increased unfilled grain (163.5%) and decreased grain index (12.9%) in the WAB cultivar. Wind speed at 35-40 km/h promoted a high percentage of grain drop (25.7%) and unfilled grains (77.3%), and low grain index (20.8 g) in WS genotype. WAB was more tolerant of wind stress than the WS. The present experiment showed that genotype had different responses to wind and rain treatments implying different mitigation strategies should be applied through genotype selection.

Understanding the genetic and environmental factors that structure root-associated microbiomes is necessary to inform rice (Oryza sativa L.) breeding and fertilizer. Herein, we comprehensivly explored the microbiomes along four fine-scale root compartments, bulk soil, rhizosphere, rhizoplane and endosphere, between traditional Japonica rice and improved hybrid rice acorss three spatially distant locations. Bacterial diversity decreased monotonically from external bulk soil to internal endosphere. The acquisition of endosphere symbionts is governed conjointly by a two-step selection process and an amplification selection process, which depends on the bacterial functional group. The bacterial communities are primarly affected by root compartment and planting location, followed by relatively samll but signifcant rice genotype effect. The exterior bulk soil, rhizosphere and rhizoplane communities are govrned by variable selection. In contrast, the internal endosphere counterparts are shapped by homogenizing selection, which are undiscernible between the two rice genotypes. After ruling out planting location effect, we screened 12 rice genotype-discriminatory orders that contributed an overall 97.22 % accuracy in diagnosing rice genotype. Hybrid rice is inferior to Japonica rice in carbon and nitrogen fixation, nitrogen and phosphorus biomineralization from organic sources. Collectively, we proposed a conceptual model to infer rice genotype effect on the rhizosphere microbiomes, and the subsequent requirement of external fertilizer for sustaining yield. Our findings deepen our understanding of the complex rice genotype–root microbiomes–fertilizer interactions from the prespective of microbially-mediated nutrient cycles. • Endosphere microbes is acquired by two-step selection and amplification-selection processes. • Homogeneous selection governs interior endosphere bacterial assembly, variable selection shapes exterior compartments. • Rice genotype-discriminatory orders contribute 97.2 % accuracy for diagnosing genotype. • Hybrid rice is inferior to Japonica rice in the acquisition of bioavailable nutrients from organic sources. • A conceptual model among rice genotype, rhizosphere microbiome and yield is proposed. [ABSTRACT FROM AUTHOR]

"Late spring coldness" (T) is a frequent meteorological disaster in the spring in southern China, often causing severe yield losses of direct-seeded early rice. In this study, we investigated the mechanisms underlying the differences in the compensatory growth ability of different rice genotypes by focusing on agronomic traits, physiological indicators, and transcriptome. The results showed that there were significant differences in the compensatory growth recovery ability of different genotypes after a combination of four days of low temperature and weak light stress. Only the strong compensatory growth genotype B116 was able to grow rapidly and reduce soluble protein and H2O2 concentrations rapidly after stress. By analyzing enzyme activity as well as endogenous hormone concentration, we found that the high superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and high levels of abscisic acid (ABA) could reduce the damage of B116 during stress. Meanwhile, higher glutamine synthetase (GS) and nitrate reductase (NR) activity and higher levels of gibberellin A3(GA3), indoleacetic acid (IAA), and zeatin nucleoside (ZR) could enable B116 to grow rapidly after stress. The identified differentially expressed genes (DEGs) indicated that there were large differences in POD-related genes and gibberellin metabolism between B116 and B144 after stress; RT-PCR quantification also showed a trend consistent with RNA-seq, which may be an important reason for the differences in compensatory growth ability. [ABSTRACT FROM AUTHOR]

To mitigate the impact of extreme weather incidents, rice cultivars Way Seputih (WS) and Way Apo Buru (WAB) were evaluated under simulation of continuous wind and rainfall treatments. The research was conducted from July to October 2017 at Leuwikopo Experimental Farm, Bogor, Indonesia. For 15 days at day time, flowering rice hills were treated with about 100 mm/h water shower (Experiment-1), and with 0, 10-15, 20-25 and 35-40 km/h wind velocity (Experiment-2). Results showed that wind and rainfall treatments reduced rice production; the effect depended on the genotypes and flowering stage. Rain treatment from panicle emergence to 50%-emerged increased the number of unfilled grains by 154.6-182.3% and 55.7-101.9% in WS and WAB cultivars, respectively. Rain treatment at 100%-emerged had no effect on WS, but it increased unfilled grain (163.5%) and decreased grain index (12.9%) in the WAB cultivar. Wind speed at 35-40 km/h promoted a high percentage of grain drop (25.7%) and unfilled grains (77.3%), and low grain index (20.8 g) in WS genotype. WAB was more tolerant of wind stress than the WS. The present experiment showed that genotype had different responses to wind and rain treatments implying different mitigation strategies should be applied through genotype selection. [ABSTRACT FROM AUTHOR]

Ionomic profiles are primarily influenced by genetic and environmental factors. Identifying ionomic responses to varietal effects is necessary to understand the ionomic variations among species or subspecies and to potentially understand genetic effects on ionomic profiles. We cultivated 120 rice (Oryza sativa) varieties to seedling stage in identical hydroponic conditions and determined the concentrations of 26 elements (including 3 anions) in the shoots and roots of rice. Although the subspecies effects were limited by the genus Oryza pre-framework and its elemental chemical properties, we found significant differences in ionomic variations in most elements among the aus , indica and japonica subspecies. Principal component analysis of the correlations indicated that variations in the root-to-shoot ionomic transport mechanisms were the main causes of ionomic differences among the subspecies. Furthermore, the correlations were primarily associated with the screening of varieties for elemental covariation effects that can facilitate breeding biofortified rice varieties with safe concentrations of otherwise toxic elements. The japonica subspecies exhibited the strongest elemental correlations and elemental covariation effects, therefore, they showed greater advantages for biofortification than the indica and aus subspecies, whereas indica and aus subspecies were likely safer in metal(loid) polluted soils. We also found that geographical and historical distribution significantly defined the ionomic profiles. Overall, the results of this study provided a reference for further association studies to improve the nutritional status and minimize toxicity risks in rice production. [ABSTRACT FROM AUTHOR]

Experimental studies were conducted to estimate the possible damage caused to ten rice (Oryza sativa L.) genotypes of Pakistan by tropospheric ozone. The experimental site is located at 31.4504° N and 73.1350° E, at an altitude of 184 m.a.s level with an average annual rainfall of 784 mm. A suitable and agile method was adopted to assess tolerance and susceptibility in rice genotypes at an early growth stage. Genotype Injury response, growth and biochemical parameters were measured to estimate possible effects of ozone, which was subsequently proclaimed as a criterion for ozone tolerance. Rice genotypes were subjected to ozone concentrations of 70 pbb (Current ambient) and 120 pbb (expected in near future) under a polytunnel. The findings indicated that ozone, an atmospheric pollutant, substantially harmed crop growth and metabolism, as well as inflicted a specific type of foliar injury that caused early leaf senescence. Rice genotype IR-9 followed by Punjab-Basmati and Ksk-434 appeared to be the most susceptible, whereas Basmati-515 followed by Basmati 2000 and super-Basmati were found to be Ozone-tolerant. Plant genotypes grown under elevated ozone showed 13.45% and 11.35% reduction in total root and shoot dry weight, and 25.54% and 6.6% decrease in plant leaf area and plant total length respectively compared to the control group. A significant interaction between treatment × chemical components and growth parameters was also found. The Present study confirms a direct relationship between visual response and growth as well as biochemical parameters. Declared results were statistically analyzed by using analysis of variance at confidence level of p < 0.05.

“Late spring coldness” (T) is a frequent meteorological disaster in the spring in southern China, often causing severe yield losses of direct-seeded early rice. In this study, we investigated the mechanisms underlying the differences in the compensatory growth ability of different rice genotypes by focusing on agronomic traits, physiological indicators, and transcriptome. The results showed that there were significant differences in the compensatory growth recovery ability of different genotypes after a combination of four days of low temperature and weak light stress. Only the strong compensatory growth genotype B116 was able to grow rapidly and reduce soluble protein and H2O2 concentrations rapidly after stress. By analyzing enzyme activity as well as endogenous hormone concentration, we found that the high superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and high levels of abscisic acid (ABA) could reduce the damage of B116 during stress. Meanwhile, higher glutamine synthetase (GS) and nitrate reductase (NR) activity and higher levels of gibberellin A3(GA3), indoleacetic acid (IAA), and zeatin nucleoside (ZR) could enable B116 to grow rapidly after stress. The identified differentially expressed genes (DEGs) indicated that there were large differences in POD-related genes and gibberellin metabolism between B116 and B144 after stress; RT-PCR quantification also showed a trend consistent with RNA-seq, which may be an important reason for the differences in compensatory growth ability.

Rice (Oryza sativa L.) is the staple food of more than three billion people in the world. The trend of increasing submergence has a negative effect on the rice yield but some of the rice genotypes show the excellent performance to give a satisfactory yield under submergence stress. Screening is very effective and reliable technique for submergence stress. The total of thirty rice genotypes including four modern varieties and twenty-six advanced lines were used for screening them against submergence tolerance by morphological analysis in the farm yard of Genetics and Plant Breeding division at Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh following modified hydroponic method. The experimental treatments comprised two factors, Factor A: Thirty T. aman rice genotypes; Factor B: Submerged condition and non-submerged control condition. The rice genotypes with diverse genetic background were used for screening of submergence tolerance at reproductive stages. The phenotypic co-efficient of variation (PCV) was higher than the genotypic co-efficient of variation (GCV) for all the characters studied indicating that they all interacted with the environment to some extent. The heritability for all characters was in the range of 62.44% to 99.42% and the highest heritability was found in number of filled grain panicle-1 (99.42%). The performance of the genotypes with respect to yield and yield components differed from each other under submergence and non-submergence conditions. Yield and yield components of the genotypes reduced in submergence condition. IR 28, IR 16, IR 18, IR 05, IR 06, IR 07, IR 24 were identified as tolerant to submergence stress. All tolerant genotypes showed higher plant height, number of total tillers plant-1 number of effective tillers plant-1, panicle length, number of filled grains panicle-1, 1000-grain weight and yield plant-1, respectively. Therefore, identified genotypes are considered promising rice varieties tolerant to submergence stress. [ABSTRACT FROM AUTHOR]

In worldwide production, rice is the second-most-grown crop. It is considered a staple food for many populations and, if naturally enriched in Se, has a huge potential to reduce nutrient deficiencies in foodstuff for human consumption. This study aimed to develop an agronomic itinerary for Se biofortification of Oryza sativa L. (Poaceae) and assess potential physicochemical deviations. Trials were implemented in rice paddy field with known soil and water characteristics and two genotypes resulting from genetic breeding (OP1505 and OP1509) were selected for evaluation. Plants were sprayed at booting, anthesis and milky grain phases with two different foliar fertilizers (sodium selenate and sodium selenite) at different concentrations (25, 50, 75 and 100 g Se·ha−1). After grain harvesting, the application of selenate showed 4.9–7.1 fold increases, whereas selenite increased 5.9–8.4-fold in OP1509 and OP1505, respectively. In brown grain, it was found that in the highest treatment selenate or selenite triggered much higher Se accumulation in OP1505 relatively to OP1509, and that no relevant variation was found with selenate or selenite spraying in each genotype. Total protein increased exponentially in OP1505 genotype when selenite was applied, and higher dosage of Se also increased grain weight and total protein content. It was concluded that, through agronomic biofortification, rice grain can be enriched with Se without impairing its quality, thus highlighting its value in general for the industry and consumers with special needs.

Terminal drought stress is one of the restrictive factors in rice production and is expected to upsurge under the current situation of climate change. The study evaluated the performance of 2030 rice genotypes under continuous drought stress conditions based on days to flowering (DF). The genotypes under augmented randomized complete block design were sown in May/June of 2017 and 2018 in the field with movable rainout that resulted in huge genetic diversity among the accessions. Descriptive statistics confirmed clear variation among accessions on growth duration, plant height to leaf, plant height to panicle, and germination percentage. Correlation, chemometric, and agglomerative hierarchical cluster analyses were performed that categorized the germplasm into 10 groups. Genotypes in clusters VIII and IX (drought-resistant) revealed better agronomic performance in terms of reduced days to flowering, but conversely taller plant height and higher maturity (%) under severe stress. Genotypes in clusters IV, V, and X were discovered to be drought-susceptible. The screened genotypes like Longjing 12, Longdun 102, Yanjing 22, Liaojing 27, Xiaohongbandao, Songjing 17, and Zaoshuqingsen can be utilized in rice breeding improvement programs for drought tolerance in terms of severe continuous drought, as well as terminal drought stress.

To assist with rapid screening for rice blast resistance as a precursor in a breeding program, the susceptibility to rice blast of 13 rice genotypes from Australia was evaluated in May to June 2013 using three distinct inoculation methods (spot, filter paper and standard methods) at seedling, vegetative and reproductive stages. The results revealed that the spot and filter paper inoculation methods were successful in discerning susceptibility to the rice blast disease (P ≤ 0.05). Disease susceptibility declined significantly from the vegetative to reproductive stages. The standard method was conducted at three different stages for pot plants grown inside the mist house. However, low temperatures did not produce disease symptoms except in a few genotypes. Among the 13 rice genotypes screened, AAT9 expressed a highly resistant response, and AAT4, AAT6, AAT10, AAT11, AAT13, AAT17 and AAT18 expressed resistance at various stages. The results will be useful for selecting elite genotypes for disease tolerance where rice blast is prevalent. In addition, the resistant genotypes can serve as a gene pool used in breeding programmes to develop new resistant genotypes.

Cnaphalocrocis medinalis Guenée is a noxious rice pest during cultivated periods. Cnaphalocrocis medinalis moths lay eggs on leaf surfaces, and larvae longitudinally roll the leaves to hide inside the leaf buds and feed on the upper epidermis and mesophyll tissues. In this study, we evaluated the female oviposition preference and larval performance of C. medinalis on six insect-resistant and six insect-susceptible rice genotypes. Female moth choice and no-choice oviposition preferences were studied. The number of eggs laid on the leaf varies among selected rice genotypes; however, female adults prefer to lay more eggs on both some resistant and susceptible rice genotypes. Furthermore, newly hatched larvae showed no observed differences in preference for both specific resistant and susceptible rice genotypes. The time taken by larvae for leaf selection varied significantly after inoculation on different genotypes at the maximum tillering and heading stages of rice plants. Compared with susceptible genotypes, leaf selection time was prolonged in resistant genotypes. In addition, the time taken for folding primary vegetative and flag leaves by larvae varied among the selected rice genotypes; larvae required more time to fold leaves of resistant than susceptible genotypes. In host antibiosis tests, larval and pupal survival and pupal weight were higher in susceptible than resistant genotypes. The results showed that the time required by larvae for leaf rolling and host antibiosis should be considered as the most crucial factors for rice genotypes resistant to C. medinalis. [ABSTRACT FROM AUTHOR]

The aims of the present study were to determine the optimum sowing time of newly developed rice genotypes for high crop water productivity in non-flooded dry-seeded rice (DSR) in north-west India, and to identify the factors underlying high yielding genotypes by comparing their sink production in DSR. We evaluated differences in dry matter, nitrogen accumulation, translocation, yield formation and evapo-transpiration requirement of the selected genotypes developed for DSR (two cultivars; PR-115 and PR-121, two recombinant inbred lines; RIL-367 and RIL-1649) under three sowing dates (1, 10, and 20 June), for two years in the rainy seasons of 2014 and 2015 in north-west India. RIL-1649 sown on 1 June had higher grain yield (9.4 t ha −1 ) and similar or higher water productivity (1.3 kg m −3 ) than the other sowing date x genotype combinations. Delaying sowing from 1 to 10 June reduced yield of all genotypes except PR-121, and there was no further decrease in yield with delay to 20 June of PR-115 and RIL-1649. The yield of RIL-1649 sown on 20 June (7.9 t ha −1 ) was similar to that of PR-115 sown on 1 June.The high grain yield of RIL-1649 (7.9 t ha −1 ) for the late sowing was due to high pre- and post-anthesis dry matter accumulation, coupled with greater contribution of dry matter translocation to grain yield. RIL-367 not only produced similar yield (8.5 t ha −1 ) to the check variety PR-115 (8.3 t ha −1 ) for the 1 June sowing, but also matured 13 days earlier than PR-115.These results suggest that RIL-367 could be useful for DSR-based intensive cropping systems in north-west India, and with higher crop water productivity (1.32 kg m −3 ) than PR-115 (1.20 kg m −3 ). In the late sown condition, grain yield had a positive relationship with harvest index, leaf area index at flowering, preanthesis dry-matter accumulation, and dry matter translocation. A greater amount of dry matter and nitrogen uptake at anthesis, in combination with an increased harvest index, resulted in a greater amount of translocated material during the grain filling period. This, in turn, contributed to higher grain yield during late sowing. This study suggests that, for widening the sowing window, and for sustained yields of DSR in north-west India, high dry matter and nitrogen accumulation at anthesis, together with high harvest index, are useful selection traits. [ABSTRACT FROM AUTHOR]

Arsenic (As) exposure from rice consumption has now become a global health issue. This study aimed to investigate the effects of rice rhizosphere oxic conditions on silicate transporter (responsible for arsenite transportation) expressions, and on As accumulation and speciation in four rice genotypes, including two hybrid genotypes (Xiangfengyou9, Shenyou9586) and two indica subspecies (Xiangwanxian17, Xiangwanxian12). Oxic and anoxic treatments have different effects on root length (p < 0.001) and weight (p < 0.05). Total As concentrations in roots were dramatically lower in oxic treatments (88.8–218 mg/kg), compared to anoxic treatments (147–243 mg/kg) (p < 0.001). Moreover, root and shoot arsenite concentrations in oxic treatments were lower than that in anoxic treatments in arsenite treatments. The relative abundance of silicate transporter expressions displayed a trend of down-regulation in oxic treatments compared to anoxic treatments, especially significantly different for Xiangwanxian17, Xiangwanxian12 in Lsi1 expressions (p < 0.05), Xiangfengyou9, Shenyou9586, Xiangwanxian17 in Lsi2 expressions (p < 0.05). However, there were no significant differences of transporter expressions in different As treatments and genotypes. It may be a possible reason for low As accumulation in rice growing aerobically compared to flooded condition and a potential route to reduce the health risk of As in rice. [ABSTRACT FROM AUTHOR]

Plant responses to nitrogen (N) and phosphorus (P) deficiencies differ among genotypes. Although the rhizosphere microbiome can serve as an indicator of plant functional traits across different genotypes, whether and how genotypic differences in plant tolerance to N and P deficiencies are associated with the rhizosphere microbiome are unknown. In this study, we carried out a paddy field experiment using five previously screened rice (Oryza sativa L.) varieties and examined crop yield and mineral element concentrations as well as the chemical properties and bacterial community of bulk and rhizosphere soils in response to N and P deficiencies. The three high-yield rice genotypes were found to be tolerant to N and P deficiencies, whereas the two low-yield genotypes were sensitive. Rhizosphere bacterial community compositions under different fertilization treatments were clearly separated into two groups corresponding to tolerant and sensitive rice. Eighteen bacterial keystone taxa were identified across the five rice genotypes under different N and P conditions. Tolerant rice harbored more bacterial keystone taxa in the rhizosphere under N or P deficiency than did sensitive rice. The specific bacterial keystone taxa recruited by tolerant rice were functionally associated with soil N transformation, plant-promoting activity, carbon decomposition, and iron cycling. These results suggest that bacterial community selection in the rhizosphere is dependent on the tolerance of rice genotypes to N and P deficiencies. The findings help explain the intrinsic mechanism that potentially controls the yield gap of rice genotypes through rhizosphere-driven microbial functions under N/P-limited agroecosystem conditions. The identified bacterial keystone taxa, which are potentially useful bio-fertilizer inoculants for agricultural production and possible indicators of rice genotypes for breeding N- and P-efficient rice cultivars, may ultimately contribute to sustainable agricultural development, resulting in high crop yields while minimizing fertilizer input and environmental risks. • Fertilization has a greater effect than rice genotype on the bacterial community. • Bacterial community selection in the rhizosphere is rice-genotype dependent. • Rice tolerance to N/P deficiency drives separation of the bacterial community. • Compared with sensitive rice, tolerant rice harbors more bacterial keystone taxa. • Bacterial keystone taxa are associated with C/N transformation and Fe cycling. [ABSTRACT FROM AUTHOR]

Nitrification and denitrification are important processes in the biogeochemical cycle in agricultural soils and are influenced by plant genotype and nitrogen (N) fertilization. However, few studies have evaluated the effects of genotype on nitrification and denitrification in the rhizosphere of rice cultivated in mudflats and their response to N fertilization. In this study, we determined the net nitrification and denitrification rates, quantified the abundance of functional genes involved in nitrification and denitrification, and characterized bacterial communities in the rhizosphere of two rice varieties (japonica and hybrid rice) cultivated in mudflat soil with three N fertilization levels. Results showed that net nitrification rates were strongly influenced by genotype and was higher in the rhizosphere of hybrid rice than in that of japonica rice, which might be related to the N absorption strategy of rice, while net denitrification rates were mainly affected by N fertilization. Unlike hybrid rice, the net nitrification rate in the rhizosphere of japonica rice was strongly influenced by N fertilization and positively correlated to N fertilization levels. In contrast, the net denitrification rate of hybrid rice was strongly influenced by N fertilization and positively correlated to N fertilization levels, while N fertilization had no significant effect on the net denitrification rate of japonica rice. Ammonia-oxidizing bacteria were the main drivers of nitrification in the rhizosphere, and denitrification in the rhizosphere of hybrid rice was mainly driven by nar G-, nir S-, and nor B-type denitrifiers. Furthermore, differences in the assemblages of bacteria associated with the relative abundance of these functional genes provided insight into genotypic differences in nitrification and denitrification responses to N fertilization. Overall, this study provides insight into the underlying mechanisms of nitrification and denitrification influenced by rice genotypes and N fertilization in the rhizospheres of japonica and hybrid rice. [ABSTRACT FROM AUTHOR]

Background: Majority of the Asian people depend on rice for nutritional energy. Rice cultivation and yield are severely affected by soil salinity stress worldwide. Marker assisted breeding is a rapid and efficient way to develop improved variety for salinity stress tolerance. Genomic microsatellite markers are an elite group of markers, but there is possible uncertainty of linkage with the important genes. In contrast, there are better possibilities of linkage detection with important genes if SSRs are developed from candidate genes. To the best of our knowledge, there is no such report on SSR markers development from candidate gene sequences in rice. So the present study was aimed to identify and analyse SSRs from salt responsive candidate genes of rice. Results: In the present study, based on the comprehensive literature survey, we selected 220 different salt responsive genes of rice. Out of them, 106 genes were found to contain 180 microsatellite loci with, tri-nucleotide motifs (56%) being most abundant, followed by di-(41%) and tetra nucleotide (2.8%) motifs. Maximum loci were found in the coding sequences (37.2%), followed by in 5'UTR (26%), intron (21.6%) and 3'UTR (15%). For validation, 19 primer sets were evaluated to detect polymorphism in diversity analysis among the two panels consisting of 17 salt tolerant and 17 susceptible rice genotypes. Except one, all primer sets exhibited polymorphic nature with an average of 21.8 alleles/primer and with a mean PIC value of 0.28. Calculated genetic similarity among genotypes was ranged from 19%-89%. The generated dendrogram showed 3 clusters of which one contained entire 17 susceptible genotypes and another two clusters contained all tolerant genotypes. Conclusion: The present study represents the potential of salt responsive candidate gene based SSR (cgSSR) markers to be utilized as novel and remarkable candidate for diversity analysis among rice genotypes differing in salinity response. [ABSTRACT FROM AUTHOR]

To assist with rapid screening for rice blast resistance as a precursor in a breeding program, the susceptibility to rice blast of 13 rice genotypes from Australia was evaluated in May to June 2013 using three distinct inoculation methods (spot, filter paper and standard methods) at seedling, vegetative and reproductive stages. The results revealed that the spot and filter paper inoculation methods were successful in discerning susceptibility to the rice blast disease ( P ≤ 0.05). Disease susceptibility declined significantly from the vegetative to reproductive stages. The standard method was conducted at three different stages for pot plants grown inside the mist house. However, low temperatures did not produce disease symptoms except in a few genotypes. Among the 13 rice genotypes screened, AAT9 expressed a highly resistant response, and AAT4, AAT6, AAT10, AAT11, AAT13, AAT17 and AAT18 expressed resistance at various stages. The results will be useful for selecting elite genotypes for disease tolerance where rice blast is prevalent. In addition, the resistant genotypes can serve as a gene pool used in breeding programmes to develop new resistant genotypes. [ABSTRACT FROM AUTHOR]

Rice being a major crop of Pakistan contributes major part of our economy and provides energy to a major population. So study was carried out to determine potential of nutritive losses in six rice genotypes against red flour beetle, Tribolium castaneum (Herbst) at 28°C, 32°C and 35°C. For nutritive losses, crude protein, fiber, ash and moisture content was analyzed through proximate analysis after 90 days of beetle infestation. Results deduced from the present findings shown significantly (P < 0.05) substantial variations in nutritional composition of rice grains in some advanced rice genotypes when exposed to artificial infestation of red flour beetle. High moisture content was observed in KSK-133 and Basmati-2006 as compared to KSK-282. Loss in crude fat and protein were maximum in KSK-282 and minimum in KSK-133 and Basmati-2006. Crude fiber was significantly (P < 0.05) high where insect infestation was low and least value where maximum infestation caused by insect. Ash content was severely affected by destructive activity of insects in all genotypes. In aggregate qualitative losses were significantly (P < 0.05) high in KSK-133, Basmati-2006 and Basmati-515 and low in Basmati-385 and KSK-133 proving susceptible and resistance respectability, respectively. Findings should be incorporate in breeding programme and can also be helpful in post-harvest storage. [ABSTRACT FROM AUTHOR]

Abstract: Folding and spinning behavior of Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae) in different categories of rice genotypes viz., resistant, susceptible, hybrid, scented, popular and wild rice genotypes were significantly different. Longer leaf selection time and folding time per primary fold; shorter primary fold and whole leaf fold; lower number of binds per primary fold and whole leaf fold were recorded in resistant and wild rice genotypes. In the correlation analysis, it was found that the leaf folding parameters were positively correlated to leaf folder damage whereas the leaf spinning parameters were negatively correlated. Similarly, the morphological characters differed significantly among the chosen genotypes and were related to leaffolder damage. The leaf width and total productive tiller number were positively correlated to leaffolder infestation. Results also indicated that the trichome density and length, leaf length and plant height might contribute to resistance whereas total number of green leaves had no effect on leaffolder infestation. In the scatter plot analysis between leaf folding and spinning characters and leaffolder damage, the genotypes were separated into four groups viz., resistant (TKM6, Ptb 33, LFR831311, Oryza rhizomatis and O. minuta), moderately resistant (ASD16 and CORH1), moderately susceptible (ADT36, Pusa Basmati and CB200290) and susceptible (IR36 and TN1). The present investigation proved that the leaf morphology viz., leaf length and width, plant height and trichome density and length may play a vital role in resistance against rice leaffolder. [Copyright &y& Elsevier]

Abstract: The experiment was carried out to assess the reaction of different categories of rice genotypes viz., resistant, susceptible, hybrid, scented, popular and wild in response to the infestation by rice leaffolder (RLF), Cnaphalocrocis medinalis (Guenee) and to explore the possible use of these genotypes in developing RLF-resistant rice varieties. The changes of various biochemical constituents such as leaf soluble protein, phenol, ortho-dihydroxy phenol, tannin and enzymes viz., peroxidase, phenyl alanine ammonia lyase (PAL) were assessed spectrophotometrically in all the rice genotypes before and after RLF infestation. The protein profile was analyzed using sodium dodecyl sulphate-poly acrylamide gel electrophoresis (SDS-PAGE) method. A significant constituent of biochemical content such as tannin, phenol and ortho-dihydroxy phenol has been increased along with enzyme activities of peroxidase and PAL in the infested resistant (Ptb 33, TKM6 and LFR831311) and wild rice genotypes (Oryza minuta and O. rhizomatis). A decrease in leaf protein content was evident invariably in all the infested rice genotypes. It is also evident that the contents of biochemicals such as phenol, ortho-dihydroxy phenol and tannin were negatively correlated with leaffolder damage. However, leaf protein content was positively correlated with the damage by rice leaffolder. SDS-PAGE analysis for total protein profiling of healthy and C. medinalis-infested genotypes revealed the enhanced expression of a high molecular weight (> 97 kDa) protein in all the genotypes. Besides, there was also an increased induction of a 38 kDa protein in C. medinalis infested resistant genotypes, which was absent in uninfested plants. The present investigation proved that the elevated levels of biochemicals and enzymes may play a vital role in rice plants resistance to RLF. [Copyright &y& Elsevier]

Abstract: Effects of shading at the flowering and grain filling stages on osmotic regulation substance content and protective enzyme activities in the leaves of different rice genotypes (e.g., IIyou 498, Gangyou 188, Dexiang 4103, Gangyou 527 and Chuanxiang 9838) were investigated. The results showed that the malondialdehyde content of Gangyou 188 significantly increased under shading, whereas those of IIyou 498, Dexiang 4103, Gangyou 527 and Chuanxiang 9838 showed no significant differences compared to the control. The soluble sugar content significantly decreased in IIyou 498, Gangyou 188, Dexiang 4103 and Chuanxiang 9838, whereas it did not significantly increase in Gangyou 527 under the weak light conditions (shading). Moreover, the soluble protein content in the leaves of different genotypes tended to decrease under shading. Further, the protective enzyme activities in the leaves varied in different rice genotypes under the shading treatment. Based on the osmotic regulation substance content and the protective enzyme activities in the leaves of different rice genotypes, it was concluded that Gangyou 188 and Gangyou 527 had strong abilities to adapt to the low light conditions. In addition, the mechanism of damage to rice leaves in different genotypes under shading was discussed. [Copyright &y& Elsevier]

Abstract: Human exposure to toxic heavy metals via the food chain is of increasing concern. In the present study, the effects of soil type and genotype on variation in arsenic (As) concentrations of different organs were investigated by using nine rice cultivars grown in two soils, with two levels of As contamination. There were significant genotypic differences (P <0.05) in As concentrations of all organs, and As concentrations of polished grain were significantly affected by genotype and soil type. The As concentration in polished grain was higher in red paddy soil under As treatment, with range from 0.24 to 1.03mgkg−1, and the As concentration of three cultivars exceeded the concentration of Chinese Food Hygiene Standard (0.7mgkg−1). The As concentrations in stems, leaves and polished grain were all significantly and positively correlated. The As concentrations in polished grain were positively and significantly (P <0.01) correlated with As root–grain translocation factor. The results indicated that As concentration in grain was partially governed by As uptake and the transfer of As from root to grain. The grain As concentration of the nine cultivars was significantly correlated between the two soil types at different levels of As contamination. Some genotypes, such as japonica rice (e.g. Ning jing 1 and Nan jing 32) had consistently low grain As concentrations. The results suggest the possibility of breeding the As rice cultivars to produce grain for safe consumption from soils with slight and moderate levels of As. [Copyright &y& Elsevier]

Abstract: The objective of this study was to understand the relationship between cooking quality and lipid content and components in milled rice of different cultivars, and the regulation of nitrogen on lipid quality in japonica rice (Oryza sativa L.). Under 7 nitrogen conditions with 4 total nitrogen levels and 2 split ratios, the RVA parameters and contents of crude lipid, lipid components, and amylose were assayed in 6 cultivars. Genotype significantly affected the content and components of lipid in milled rice. The milled rice of small-panicle cultivars had higher contents of crude lipid and starch lipid and lower non-starch lipid in milled rice than that of the large-panicle cultivars. The effect of nitrogen on lipid content and components in milled rice was smaller than that of genotype, and varied among genotypes. The content of crude lipid was significantly and negatively correlated with breakdown value, and the content of starch lipid was significantly and negatively correlated with amylose content, setback value, and consistency viscosity. The results indicate that rice cooking quality can be promoted through cultivar improvement aiming at increasing starch lipid content in milled rice. [Copyright &y& Elsevier]

The relationship between tolerance to Zn-deficiency and Zn-dense in grain was examined. The results showed that the plant height and leaf growth rate (number) decreased more in the Zn-dense genotype (Biyuzaonuo) than in the Zn-efficient genotype (IR8192) when grown at pZn2+ ≥ 11.0. Shoot dry matter yield decreased about 6 times for the dense CV whereas only around 3 times for the efficient CV at Zn activities pZn2+ 9.7-11.4. Zinc uptake by the whole plant was greater in the Zn-dense genotype than in the Zn-efficient genotype, and the lowest in the Zn-inefficient genotype grown at pZn2+ ≥ 11.0. However, both the efficient and the dense cultivars showed higher Zn translocation efficiency at low Zn activity. These results indicate that Zn uptake by rice seedling and translocation might be more suitable than growth parameters for identifying Zn-efficient and Zn-dense genotype at seedling stage. [ABSTRACT FROM AUTHOR]

Genotypic differences in arsenic (As) and cadmium (Cd) uptake and their translocation within rice seedlings grown in solution culture were investigated. Arsenic uptake and its translocation differed significantly between eight cultivars. The largest shoot and root As concentrations were found in cultivar 'TN1' and 'ZYQ8', while cultivar 'JX-17' had the lowest As concentration. Arsenic concentration in shoot or root of 'JX-17' was about 50% of that in cultivar 'ZYQ8'. Specific Arsenic uptake (SAU) was found significantly different between rice cultivars, which was about 2-fold higher of 'ZYQ8' than that of 'JX-17'. The Cd accumulation also differed significantly between cultivars. Rice cultivar 'JX-17' had the highest ability in Cd uptake, but the lowest ability in Cd translocation from root to shoot. The transfer factor (TF) of Cd had an important effect on Cd accumulation by rice seedlings. Arsenic can competitively inhibit P uptake by rice seedlings, P concentrations in shoots, or roots treated with As were significantly lower than those without As addition. However, the concentrations of P and As were positively correlated within these genotypes. The Cd immobilization by cell wall was an important mechanism for Cd detoxification. The cell wall bound 21-44% of total Cd in shoots and 25-59% of total Cd in roots of these tested genotypes. The genotypic differences in As and Cd uptake and translocation within rice seedlings provide the possibility of selecting and breeding genotypes and /or cultivars with reduced levels of As and Cd in rice grains. [ABSTRACT FROM AUTHOR]

The technological behavior of extruded rice flours from seven genotypes, using a baking test to elaborate bread without gluten, was studied comparing them with the performance of the same samples without extrusion treatment. Rice flours were extruded using two levels of hydration: 15 and 30%. Baking tests were carried out with such hydration levels to obtain, in different mixtures, the same consistency before baking. Bread quality was evaluated by assessing sensory attributes using a trained panel. When no-waxy rice flour was 100% replaced in the recipe by the same flour but extruded with 15% moisture, bread volume was improved 22% and crumb structure quality 120%. Nevertheless, when rice flours of waxy genotypes, extruded at moisture level of 15% or 30% were used in the formulation, volume improved 41% and crumb structure 142%. These waxy genotypes are then especially suitable for making bread without gluten. Resumen Se estudió el comportamiento, en la elaboración de pan sin gluten, de siete genotipos de arroz cuyas harinas fueron tratadas por extrusión y se comparó con las mismas harinas sin extrudir. Las harinas de arroz fueron extrudidas en laboratorio con dos niveles de humedad: 15 y 30%. La panificación se llevó a cabo con la hidratación necesaria para mantener la mezcla batida a consistencia constante. Los panes fueron evaluados por sus atributos sensoriales a través de un panel entrenado. Cuando en la formulación se reemplazó totalmente la harina de arroz no-waxy sin extrudir por la misma harina extrudida con 15% de humedad, mejoró el volumen del pan en un 22% y la estructura de la miga en un 120%. A su vez, cuando se reemplazó con harinas de genotipos waxy extrudidas tanto a 15% como a 30% de humedad estos atributos de calidad fueron significativamente mejores, creciendo el volumen en un 41% y la estructura de la miga en un 142%. Por lo tanto, estos genotipos waxy con tratamiento por extrusión resultan especialmente aptos para la elaboración de pan sin gluten. Palabras clave: Panificación, enfermedad celíaca, genotipos de arroz [ABSTRACT FROM PUBLISHER]

Abstract: Bicarbonate content in growth medium has been considered to be one of the major factors in inducing zinc (Zn) deficiency in lowland rice. In this study, the effects of bicarbonate on root elongation, distribution and exudation of organic acids were examined in the Zn-efficient and Zn-inefficient rice genotypes. Bicarbonate significantly increased the growth of fine roots in the Zn-efficient genotype but inhibited their growth in the Zn-inefficient genotype. In fine root zones of 2–8mm from the tip, of plants grown with bicarbonate, malate, citrate, and fumarate accumulation was greater in the Zn-inefficient genotype, but not the Zn-efficient genotype, than the control. Enhanced exudation of malate at fine root zones of 1–2cm from the tip by bicarbonate was noted in the Zn-efficient genotype, but not in the Zn-inefficient genotype. Bicarbonate induced greater exudation of citrate at fine root zones of 1–2cm from the tip in the Zn-efficient than in the Zn-inefficient genotypes. The increase in the concentrations of malate and citrate in xylem sap by bicarbonate were found to be greater for the Zn-efficient genotype than that for the Zn-inefficient genotype. The results indicated that bicarbonate-mediated inhibition of fine root elongation in the Zn-inefficient genotype might result from excessive accumulation of organic acids, particularly malate, in root elongation zones. In the Zn-inefficient rice genotype the increased accumulation of malate and citrate in fine roots by bicarbonate appeared to result from less exudation of them to the rhizosphere and transport up to the shoots. [Copyright &y& Elsevier]

Experimental studies were conducted to estimate the possible damage caused to ten rice (Oryza sativa L.) genotypes of Pakistan by tropospheric ozone. The experimental site is located at 31.4504° N and 73.1350° E, at an altitude of 184 m.a.s level with an average annual rainfall of 784 mm. A suitable and agile method was adopted to assess tolerance and susceptibility in rice genotypes at an early growth stage. Genotype Injury response, growth and biochemical parameters were measured to estimate possible effects of ozone, which was subsequently proclaimed as a criterion for ozone tolerance. Rice genotypes were subjected to ozone concentrations of 70 pbb (Current ambient) and 120 pbb (expected in near future) under a polytunnel. The findings indicated that ozone, an atmospheric pollutant, substantially harmed crop growth and metabolism, as well as inflicted a specific type of foliar injury that caused early leaf senescence. Rice genotype IR-9 followed by Punjab-Basmati and Ksk-434 appeared to be the most susceptible, whereas Basmati-515 followed by Basmati 2000 and super-Basmati were found to be Ozone-tolerant. Plant genotypes grown under elevated ozone showed 13.45% and 11.35% reduction in total root and shoot dry weight, and 25.54% and 6.6% decrease in plant leaf area and plant total length respectively compared to the control group. A significant interaction between treatment × chemical components and growth parameters was also found. The Present study confirms a direct relationship between visual response and growth as well as biochemical parameters. Declared results were statistically analyzed by using analysis of variance at confidence level of p < 0.05., Competing Interests: The authors declare no conflict of interest., (© 2021 Published by Elsevier Ltd.)

In worldwide production, rice is the second-most-grown crop. It is considered a staple food for many populations and, if naturally enriched in Se, has a huge potential to reduce nutrient deficiencies in foodstuff for human consumption. This study aimed to develop an agronomic itinerary for Se biofortification of Oryza sativa L. (Poaceae) and assess potential physicochemical deviations. Trials were implemented in rice paddy field with known soil and water characteristics and two genotypes resulting from genetic breeding (OP1505 and OP1509) were selected for evaluation. Plants were sprayed at booting, anthesis and milky grain phases with two different foliar fertilizers (sodium selenate and sodium selenite) at different concentrations (25, 50, 75 and 100 g Se·ha−1). After grain harvesting, the application of selenate showed 4.9–7.1 fold increases, whereas selenite increased 5.9–8.4-fold in OP1509 and OP1505, respectively. In brown grain, it was found that in the highest treatment selenate or selenite triggered much higher Se accumulation in OP1505 relatively to OP1509, and that no relevant variation was found with selenate or selenite spraying in each genotype. Total protein increased exponentially in OP1505 genotype when selenite was applied, and higher dosage of Se also increased grain weight and total protein content. It was concluded that, through agronomic biofortification, rice grain can be enriched with Se without impairing its quality, thus highlighting its value in general for the industry and consumers with special needs. [ABSTRACT FROM AUTHOR]

Terminal drought stress is one of the restrictive factors in rice production and is expected to upsurge under the current situation of climate change. The study evaluated the performance of 2030 rice genotypes under continuous drought stress conditions based on days to flowering (DF). The genotypes under augmented randomized complete block design were sown in May/June of 2017 and 2018 in the field with movable rainout that resulted in huge genetic diversity among the accessions. Descriptive statistics confirmed clear variation among accessions on growth duration, plant height to leaf, plant height to panicle, and germination percentage. Correlation, chemometric, and agglomerative hierarchical cluster analyses were performed that categorized the germplasm into 10 groups. Genotypes in clusters VIII and IX (drought-resistant) revealed better agronomic performance in terms of reduced days to flowering, but conversely taller plant height and higher maturity (%) under severe stress. Genotypes in clusters IV, V, and X were discovered to be drought-susceptible. The screened genotypes like Longjing 12, Longdun 102, Yanjing 22, Liaojing 27, Xiaohongbandao, Songjing 17, and Zaoshuqingsen can be utilized in rice breeding improvement programs for drought tolerance in terms of severe continuous drought, as well as terminal drought stress. [ABSTRACT FROM AUTHOR]