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In the rapid climate change scenario and subsequent rainfall patterns, drought has emerged as a bottleneck for crop production across crops, especially in rainfed rice. Drought significantly affects the development and production of most modern rice cultivars. Thus, recent breeding efforts have aimed to integrate drought tolerance traits in existing rice varieties through conventional and molecular approaches. The identification of grain yields quantitative trait loci (QTLs) under drought conditions, an important trait with high selection efficiency, may lead to the development of drought-tolerant rice varieties. The study reported the grain yield QTLs identified under the reproductive stage of drought stress in the F2-derived mapping population from Kasturi (drought-sensitive) × Chao Khaw (drought-tolerant). Thirteen QTLs (qDTYs) were identified based on two years of field data. Comparative analysis revealed two robust and consistent DTY QTLs, qDTY1.1 and qDTY8.1 , which explained the PVEs of 11.61% to 12.88% and 15.79% to 18.77%, respectively. However, qDTY1.1 was found at the nearest position to the previously identified qDTYs. Through candidate gene analysis, the identified QTL regions in chromosome 1 (qDTY1.1) and chromosome 8 (qDTY8.1) revealed seven and five candidate genes, respectively, based on gene ontology that were significantly associated with rice grain yield-related drought traits. In conclusion, this study identified key consistent drought yield QTLs in a drought-tolerant exotic landrace. The identified QTLs provide valuable insights and resources for ongoing efforts to develop drought-tolerant rice varieties. They can be further utilized in drought breeding programs to enhance the drought resilience of existing varieties or to develop new varieties. [ABSTRACT FROM AUTHOR]

Rice is an important food crop which is considered as lifeline for more than half of the world's population. Rice requires larger amount of water throughout its life cycle than other crops. Parental lines of Kasturi and Chaw Khao were evaluated and exhibited variation for panicle length, plant height and plot yield in stress condition. Association analysis also shown plant height and plot yield was positively associated with plot yield. In this study parental polymorphism survey was conducted between Kasturi and Chaw Khao using 721 microsatellite (SSR) markers spanning over the entire 12 chromosome and resulted in 95 polymorphic SSR markers. The overall polymorphism survey for all 12 chromosomes was found to be 13.17%. The highest and lowest polymorphism was noticed in chromosome 5 (17.02 %) and chromosome 10 (5.36 %), respectively. This investigation will be helpful to genotype mapping population, construction of linkage map and grain yield QTL identification for drought stress.

BACKGROUND Nutrient deficiency in humans, especially in children and lactating women, is a major concern. Increasing the micronutrient concentration in staple crops like rice is one way to overcome this. The micronutrient content in rice, especially the iron (Fe) and zinc (Zn) content, is highly variable. The identification of rice genotypes in which there are naturally high Fe and Zn concentrations across environments is an important target towards the production of biofortified rice. RESULTS: Phenotypic correlations between grain Fe and Zn content were positive and significant in all environments but a significant negative association was observed between grain yield and grain Fe and Zn. Promising breeding lines with higher Zn or Fe content, or both, were: IR 82475‐110‐2‐2‐1‐2 (Zn: 20.24–37.33 mg kg−1; Fe: 7.47–14.65 mg kg−1); IR 83294‐66‐2‐2‐3‐2 (Zn: 22–37–41.97 mg kg−1; Fe: 9.43–17.16); IR 83668‐35‐2‐2‐2 (Zn: 27.15–42.73 mg kg−1; Fe: 6.01–14.71); IR 68144‐2B‐2‐2‐3‐1‐166 (Zn: 23.53–40.30 mg kg−1; Fe: 10.53–17.80 mg kg−1) and RP Bio 5478‐185M7 (Zn: 22.60–40.07 mg kg−1; Fe: 7.64–14.73 mg kg−1). Among these, IR82475‐110‐2‐2‐1‐2 (Zn: 20.24–37.33 mg kg−1; Fe: 7.47–14.65 mg kg−1) is also high yielding with 3.75 t ha−1. Kelhrie Cha (Zn: 17.76–36.45 mg kg−1; Fe: 7.17–14.77 mg kg−1), Dzuluorhe (Zn: 17.48–39.68 mg kg−1; Fe: 7.89–19.90 mg kg−1), Nedu (Zn: 18.97–43.55 mg kg−1 Fe: 8.01–19.51 mg kg−1), Kuhusoi‐Ri‐Sareku (Zn: 17.37–44.14 mg kg−1; Fe: 8.99–14.30 mg kg−1) and Mima (Zn: 17.10–45.64 mg kg−1; Fe: 9.97–17.40 mg kg−1) were traditional donor genotypes that possessed both high grain Fe and high Zn content. CONCLUSION: Significant genotype × location (G × L) effects were observed in all traits except Fe. Genetic variance was significant and was considerably larger than the variance of G × L for grain Zn and Fe content traits, except grain yield. The G × L × year variance component was significant in all cases. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Background: Traditional rice (Oryza sativa) varieties are valuable resources for the improvement of drought resistance. qDTY3.2 is a drought-yield quantitative trait locus that was identified in a population derived from the traditional variety Moroberekan and the drought-susceptible variety Swarna. In this study, our aim was to characterize the physiological mechanisms associated with qDTY3.2. Our approach was to phenotype fifteen BC2F3.4 lines for shoot and root drought resistance-related traits as compared to Swarna in the field under well-watered and drought stress conditions. Four BC2F3.4 lines contrasting for yield under drought were selected for detailed characterization of shoot morphology, water use related traits, flowering time and root system architecture in the field as well as in controlled environments (lysimeters in a greenhouse, and gel imaging platform in a growth chamber). Results: Across five field experiments, grain yield correlated significantly with root growth along the soil profile, flowering time, and canopy temperature under drought conditions. The four selected BC2F3.4 lines showed earlier flowering time, reduced distribution of root growth to shallow soil layers which resulted in lower water uptake (between 0 and 30 cm) and drought-induced increased distribution of root growth to deep soil layers (between 30 and 60 cm) as compared to Swarna in the field. Root system architecture phenotypes were confirmed in whole root systems in lysimeters, and corresponded to higher numbers of root tips in a gel imaging platform, highlighting the potential stability of some root traits across different growth stages and systems. Conclusions: We conclude that earlier flowering time, reduced shallow root growth, and drought-induced increased deep root growth are associated with the presence of qDTY3.2 since these phenotypes were consistently observed in the selected QTL lines with full introgression of qDTY3.2. We hypothesize that the qDTY3.2 associated RSA phenotypes led to better use of water and metabolic resources which, combined with earlier flowering time, improved yield under drought. [ABSTRACT FROM AUTHOR]

The investigation conducted with 25 rice genotypes comprising both Basmati and non-basmati types revealed significant differences among the genotypes for the yield, its components and some grain quality characteristics. The magnitude of differences between PCV and GCV was relatively low for all the traits, indicating less environmental influence. The GCV was higher for the characters alkali spread value, yield per plant and effective panicles. High heritability coupled with high genetic advance as per cent of mean was recorded for days to 50% flowering, plant height, panicle length, effective panicles per plant, spikelets per panicle, filled grains per panicle, test weight, yield per plant, brown rice length, brown rice L/B ratio, kernel length, kernel L/B ratio, kernel length after cooking, elongation ratio and alkali spread value indicating the additive gene effects in the genetic control of these traits and can be improved by simple selection in the present breeding material. [ABSTRACT FROM AUTHOR]