Developing climate-resilient rice varieties (BRRI dhan97 and BRRI dhan99) suitable for salt-stress environments in Bangladesh.

Salinity variations are the main reason for rice yield fluctuations in salt-prone regions throughout the dry season (Boro season). Plant breeders must produce new rice varieties that are more productive, salt tolerant, and stable across a variety of settings to ensure Bangladesh's food sustainability. To assess the yield and stability, we used fifteen rice genotypes containing two tolerant checks BRRI dhan67, Binadhan-10 and the popular Boro rice variety BRRI dhan28 in different salinity "hotspot" in three successive years followed by additive main effects and multiplicative interaction (AMMI) model utilizing a randomized complete block (RCB) design with two replications. Parents selection was done based on estimated breeding values (EBVs). Eight parents with high EBVs (IR83484-3-B-7-1-1-1, IR87870-6-1-1-1-1-B, BR8992-B-18-2-26, HHZ5-DT20-DT2-DT1, HHZ12-SAL2-Y3-Y2, BR8980-B-1-3-5, BRRI dhan67, and Binadhan-10) might be used to develop new segregating breeding materials. Based on farmer preferences and grain acceptability, three genotypes (IR83484-3-B-7-1-1-1, HHZ5-DT20-DT2-DT1, and HHZ12-SAL2-Y3-Y2) were the winning and best ones. The above three genotypes in the proposed variety trial showed significantly higher yields than the respective check varieties, high salinity tolerance ability, and good grain quality parameters. Among them, HHZ5-DT20-DT2-DT1 and IR83484-3-B-7-1-1-1 harbored eight and four QTL/genes that regulate the valuable traits revealed through 20 SNP genotyping. Finally, two genotypes IR83484-3-B-7-1-1-1 and HHZ5-DT20-DT2-DT1 were released as high salinity-tolerant rice varieties BRRI dhan97 and BRRI dhan99, respectively in Bangladesh for commercial cultivation for sustaining food security and sustainability.

SNP Based Trait Characterization Detects Genetically Important and Stable Multiple Stress Tolerance Rice Genotypes in Salt-Stress Environments.

Soil salinity is a major constraint to rice production in coastal areas around the globe, and modern high-yielding rice cultivars are more sensitive to high salt stress, which limits rice productivity. Traditional breeding programs find it challenging to develop stable salt-tolerant rice cultivars with other stress-tolerant for the saline environment in Bangladesh due to large yield variations caused by excessive salinity fluctuations during the dry (boro) season. We examined trait characterization of 18 advanced breeding lines using SNP genotyping and among them, we found line G6 (BR9621-B-1-2-11) (single breeding line with multiple-stress-tolerant QTL/genes) possessed 9 useful QTLs/genes, and two lines (G4:BR9620-2-7-1-1 and G14: IR 103854-8-3-AJY1) carried 7 QTLs/genes that control the desirable traits. To evaluate yield efficiency and stability of 18 rice breeding lines, two years of field experiment data were analyzed using AMMI (additive main effect and multiplicative interaction) and GGE (Genotype, Genotype Environment) biplot analysis. The AMMI analysis of variance demonstrated significant genotype, environment, and their interaction, accounting for 14.48%, 62.38%, and 19.70% of the total variation, respectively, and revealed that among the genotypes G1, G13, G14, G17, and G18 were shown to some extent promising. Genotype G13 (IR 104002-CMU 28-CMU 1-CMU 3) was the most stable yield based on the AMMI stability value. The GGE biplot analysis indicates 76% of the total variation (PC1 48.5% and PC2 27.5%) which is performed for revealing genotype × environment interactions. In the GGE biplot analysis, genotypes were checked thoroughly in two mega-environments (ME). Genotype G14 (IR103854-8-3-AJY1) was the winning genotype in ME I, whereas G1 (BR9627-1-3-1-10) in ME II. Because of the salinity and stability factors, as well as the highest averages of grain yield, the GGE and AMMI biplot model can explain that G1 and G13 are the best genotypes. These (G1, G6, G13, G14, G17, and G18) improved multiple-stress-tolerant breeding lines with stable grain yield could be included in the variety release system in Bangladesh and be used as elite donor parents for the future breeding program as well as for commercial purposes with sustainable production.