Reducing water requirements and lowering environmental footprints require attention to minimize risks to food security. The present study was conducted with the aim to identify appropriate root traits enhancing rice grain yield under alternate wetting and drying conditions (AWD) and identify stable, high-yielding genotypes better suited to the AWD across variable ecosystems. Advanced breeding lines, popular rice varieties and drought-tolerant lines were evaluated in a series of 23 experiments conducted in the Philippines, India, Bangladesh, Nepal and Cambodia in 2015 and 2016. A large variation in grain yield under AWD conditions enabled the selection of high-yielding and stable genotypes across locations, seasons and years. Water savings of 5.7–23.4% were achieved without significant yield penalty across different ecosystems. The mean grain yield of genotypes across locations ranged from 3.5 to 5.6 t/ha and the mean environment grain yields ranged from 3.7 (Cambodia) to 6.6 (India) t/ha. The best-fitting Finlay-Wilkinson regression model identified eight stable genotypes with mean grain yield of more than 5.0 t/ha across locations. Multidimensional preference analysis represented the strong association of root traits (nodal root number, root dry weight at 22 and 30 days after transplanting) with grain yield. The genotype IR14L253 outperformed in terms of root traits and high mean grain yield across seasons and six locations. The 1.0 t/ha yield advantage of IR14L253 over the popular cultivar IR64 under AWD shall encourage farmers to cultivate IR14L253 and also adopt AWD. The results suggest an important role of root architectural traits in term of more number of nodal roots and root dry weight at 10–20 cm depth on 22–30 days after transplanting (DAT) in providing yield stability and preventing yield reduction under AWD compared to continuous flooded conditions. Genotypes possessing increased number of nodal roots provided higher yield over IR64 as well as no yield reduction under AWD compared to flooded irrigation. The identification of appropriate root architecture traits at specific depth and specific growth stage shall help breeding programs develop better rice varieties for AWD conditions.
With the changing climatic conditions and reducing labor-water availability, the potential contribution of aerobic rice varieties and cultivation system to develop a sustainable rice based agri-food system has never been more important than today. Keeping in mind the goal of identifying high-yielding aerobic rice varieties for wider adaptation, a set of aerobic rice breeding lines were developed and evaluated for grain yield, plant height, and days to 50% flowering in 23 experiments conducted across different location in Philippines, India, Bangladesh, Nepal, and Lao-PDR between 2014 and 2017 in both wet and dry seasons. The heritability for grain yield ranged from 0.52 to 0.90. The season-wise two-stage analysis indicated significant genotype x location interaction for yield under aerobic conditions in both wet and dry seasons. The genotype × season × location interaction for yield was non-significant in both seasons indicating that across seasons the genotypes at each location did not show variability in the grain yield performance. Mean grain yield of the studied genotypes across different locations/seasons ranged from 2,085 to 6,433 Kg ha −1 . The best-fit model for yield stability with low AIC value (542.6) was AMMI(1) model. The identified stable genotypes; IR 92521-143-2-2-1, IR 97048-10-1-1-3, IR 91326-7-13-1-1, IR 91326-20-2-1-4, and IR 91328-43-6-2-1 may serve as novel breeding material for varietal development under aerobic system of rice cultivation. High yield and stable performance of promising breeding lines may be due to presence of the earlier identified QTLs including grain yield under drought, grain yield under aerobic conditions, nutrient uptake, anaerobic germination, adaptability under direct seeded conditions, and tolerance to biotic stress resistance such as qDTY 2.1 , qDTY 3.1 , qDTY 12.1 , qNR 5.1 , AG 9.1 , qEVV 9.1 , qRHD 1.1 , qRHD 5.1 , qRHD 8.1 qEMM 1.1 , qGY 6.1 , BPH3, BPH17, GM4, xa4, Xa21, Pita, and Pita2 . The frequency of xa4 gene was highest followed by qAG 9.1 , GM4, qDTY 3.1 , qDTY 2.1 , qGY 6.1 , and qDTY 12.1 .
Water scarcity and drought have seriously threatened traditional rice cultivation practices in several parts of the world including India. In the present investigation, experiments were conducted to see if the water-efficient aerobic rice genotypes developed at UAS, Bangalore (MAS25, MAS26 and MAS109) and IRRI, Philippines (MASARB25 and MASARB868), are endowed with drought tolerance or not. A set of these aerobic and five lowland high-yielding (HKR47 and PAU201, Taraori Basmati, Pusa1121 and Pusa1460) indica rice genotypes were evaluated for: (i) yield and yield components under submerged and aerobic conditions in field, (ii) root morphology and biomass under aerobic conditions in pots in the nethouse, (iii) PEG-6000 (0, −1, −2 and −3 bar) induced drought stress at vegetative stage using a hydroponic culture system and (iv) polymorphism for three SSR markers associated with drought resistance traits. Under submerged conditions, the yield of aerobic rice genotypes declined by 13.4-20.1 % whereas under aerobic conditions the yield of lowland indica/Basmati rice varieties declined by 23-27 %. Under water-limited conditions in pots, aerobic rice genotypes had 54-73.8 % greater root length and 18-60 % higher fresh root biomass compared to lowland indica rice varieties. Notably, root length of MASARB25 was 35 % shorter than MAS25 whereas fresh and dry root biomass of MASARB25 was 10 % and 64 % greater than MAS25. The lowland indica were more sensitive to PEG-stress with a score of 5.9-7.6 for Basmati and 6.1-6.7 for non-aromatic indica rice varieties, than the aerobic rice genotypes (score 2.7-3.3). A set of three microsatellite DNA markers (RM212, RM302 and RM3825) located on chromosome 1 which has been shown to be associated with drought resistance was investigated in the present study. Two of these markers (RM212 and RM302) amplified a specific allele in all the aerobic rice genotypes which were absent in lowland indica rice genotypes.
The field experiments with thirty genotypes were conducted during June to October month of kharif, 2018 and kharif, 2019, to assess extent of variability under aerobic condition. The genotypes were sown under dry direct seeded condition using randomized block design (RBD) with three replications. Each genotype was sown in single row of 5 m length with spacing of 20 cm between rows and 15 cm between plants. Data recorded for 22 characters including different morphological and quality traits from 5 randomly selected plants of each replication and mean data used for analysis. ANOVA revealed that the mean sum of squares were highly significant difference for most of the traits. The value of PCV was higher than GCV for all the twenty-two characters. However, maximum GCV and PCV were observed for root dry weight plant-1 (31.44% and 32.17%) followed grain yield plant-1 (29.97% and 31.03%), root volume (28.62% and 29.20%), root fresh weight plant-1 (28.51% and 29.08%), biological yield plant-1 (21.86% 22.50%) and number of grains panicle-1 (20.55% and 21.37%). Rest of the traits showed moderate and low GCV and PCV. High heritability and genetic advance were recorded for the traits viz., leaf length, number of tillers plant-1, number of grains panicle-1, 1000 seed weight, root length, root volume, root fresh weight plant-1, root dry weight plant-1, kernel length-breadth ratio, grain yield plant-1, biological yield plant-1 and harvest index. The information regarding different variability will provide direction to select high yielding genotypes under aerobic condition.
Background: Basmati rice is an important cereal crop occupying a unique position in Indian agriculture. More than 90% of global rice is produced and consumed in Asia and plays a crucial role in the entry of mineral nutrients into the food chain. Identification of stable genotypes is of great significance because the environmental conditions vary from season to season and year to year. Methods: Thirty six Basmati rice genotypes were evaluated in four production environments during kharif 2016 and kharif 2017 at two locations Kaul and Uchani to study the G × E interaction for milling, appearance, cooking and eating quality parameters. The genotypes were grown in randomized block design with three replications. Result: Based on the stability analysis of Eberhart and Russell model, genotypes viz., Haryana Mahak 1, Pusa 1826-12-271-4 and HKR 06-434 were found stable across the environments for milling%, grain length before cooking and length breadth ratio before cooking, respectively.
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