Phenotypic variation in drought response for a double-haploid population of bread wheat (Triticum aestivum)

Genomics-Assisted Breeding for Drought Tolerance in Wheat (Triticum aestivum L.): Recent Advances and Future Prospects

Overall, transcription factors from the DREB, NAC, MYB, and WRKY families are still considered the primary regulatory targets, but CRISPR/Cas-based gene editing is now able to provide precise, multiplex gene modifications in polyploid wheat.

Marker–trait associations for physiological responses to irrigation and terminal drought stress in bread wheat using SSR and iPBS markers

ASSESSMENT OF INTER-TRAIT RELATIONSHIP AND IDENTIFICATION OF KEY SELECTION TRAITS FOR DROUGHT TOLERANCE IN MAIZE (ZEA MAYS L.) INBRED LINES UNDER WATER-STRESS CONDITIONS

Drought is a major constraint on crop production especially in maize. It significantly reduces productivity, affecting the livelihoods of millions and the overall economy. Malnutrition due to lack of essential nutrients like Vitamin A is another major challenge in many African countries. Breeding for pro-vitamin A drought-tolerant maize varieties is crucial to address these. Knowledge and understanding of interrelationships between grain yield and yield-related traits would ensure progress from selection in maize breeding programs through the use of appropriate selection indices. 107 pro-vitamin A maize inbred lines along with 3 testers were screened for drought tolerance in Samaru and Bagauda in 2020/2021 dry season to assess the relationship between grain yield and yield-related traits. The experiments were laid out in a 10 x 11 alpha lattice design and replicated two times using single-row plot of 5m long.  Inbred lines with high tolerant index values were identified; SLMP-59 has the highest index value (18.06) with a low yield reduction percentage of 38.07% making it the best drought response. The inbred SLMP-3 turns out to be most drought susceptible with drought index value of -12.59 and yield reduction of 83.39% The negative genotypic association of days to pollen (rg = -0.80**) and days to silking (rg = -0.79**) and phenotypic association of days to pollen (rp = -0.97***) and days to silking (rp = -0.98***) with grain yield implies that these traits are not co-inherited together with grain yield and that short anthesis silking interval period would increase grain yield due to the synchronization of pollen shedding and silking emergence. Traits associated with ear aspect are the most reliable traits for indirect selection for grain yield improvement under drought condition.

Analysis of Genetic Variation, Correlation and Path Effects for Grain Yield Enhancement in Bread Wheat (Triticum aestivum L.) under Rainfed and Irrigated Conditions

Drought constrains wheat productivity, making the identification of genetically variable and yield-associated traits important for selection under contrasting moisture regimes. This study evaluated 50 advanced bread wheat genotypes, including five standard checks, under rainfed and irrigated environments during the Rabi season of 2022–23 using a randomised block design with three replications. Two physiological and fourteen yield-related morphological traits were assessed using analysis of variance, phenotypic and genotypic coefficients of variation, broad-sense heritability, genetic advance, correlation, and path coefficient analyses. The phenotypic coefficient of variation exceeded the genotypic coefficient of variation for all traits in both environments. Canopy temperature depression at 14 days after heading (CTD 2) showed the highest PCV/GCV values, at 39.90/33.42% under rainfed and 34.26/29.45% under irrigated conditions. Productive tillers per plant and CTD 2 combined high heritability with comparatively large genetic advance in both environments. Under rainfed conditions, grain yield per plot was strongly and positively correlated with harvest index (r = 0.721), productive tillers per plant (r = 0.698), and biological yield per plot (r = 0.626). Under irrigation, the strongest positive associations were with peduncle length (r = 0.611), spike length (r = 0.606), flag leaf length (r = 0.563), and biological yield per plot (r = 0.552). Path analysis identified harvest index as the largest positive direct contributor under rainfed conditions (0.8029) and biological yield per plot under irrigated conditions (0.8620). These findings support consideration of these traits in selection across contrasting moisture regimes.

Genome wide association mapping of yield and agro-morphological traits under drought and heat stress in wheat (Triticum aestivum L.)

Assessment of gene effects for drought and yield contributing traits in rice (Oryza sativa L.)

Drought tolerance is a polygenic character controlled by polygenes and very difficult to study the gene action by line x tester analysis for improvement of drought related traits. In this situation, the present study was conducted to identify gene effects in rice for drought and yield contributing characters under drought condition by generation mean analysis. The six generations viz., P1, P2, F1, F2, BC1 and BC2  were generated in three crosses viz., PMK 4 x ADT 45, Norungan x ASD 16 and Nootripathu x Co 51. Moisture stress was imposed during 30 days after planting by withholding irrigation. During drought period, the condition of the soil was dry and fragmented. Data on yield and drought contributing traits were recorded for all six generations. The results revealed that, among the main genetic effects, dominance was positively expressed in all characters except three traits (leaf rolling, days to first flowering and harvest index). In the present study, the dominance gene effects and dominance x dominance genetic effects were predominant for grain yield and major yield contributing characters joined with duplicate type of epistasis. For enhancement of these characters, selection will be postponed to later on generations or bi-parental mating of breeding method may be followed. An additive gene effect was also significantly positive for all the characters under study. In addition, additive x additive genetic effects also significant and positive for most of the characters. In the present study revealed that, complementary gene effect was observed in drought related trait leaf rolling in all three crosses, number of grains per panicle and spikelet fertility in one cross (PMK 4 x ADT 45). Complementary epistasis was expressed in the cross Norungan x ASD 16 for harvest index. In this situation, additive gene effects were predominant. For improvement of these traits, simple selection procedure and pedigree methods of breeding to be followed.