Exploring genetic diversity and stress adaptation in bread wheat (Triticum aestivum L.) under terminal heat stress

Assessment of genetic diversity, vernalization alleles, and heat tolerance markers in bread wheat lines under water stress conditions

Bread wheat is considered one of the most important crops in Egypt and worldwide and improving its productivity under water stress is a major breeding objective. This study aimed to evaluate advanced bread wheat lines under water stress and to characterize heat shock protein (HSP) and vernalization (Vrn) genes, as well as to assess genetic diversity and population structure among 19 lines using Start codon targeted (SCoT) markers. Analysis of variance revealed highly significant differences for all tested traits. Two lines (L3 and L14) recorded the lowest values for days to heading and reached maturity in a shorter period compared to the check cultivar. Seven lines (L27, L25, L20, L21, L5, L19, and L13) showed the highest grain yield. A weak relationship was observed between plant height and grain yield; however, high-yielding lines tended to be shorter. Spike number per plant showed the strongest positive correlation with grain yield (r = 0.77), indicating that it is the main determinant of yield. In addition, 1000-grain weight showed a weak positive correlation with grain yield (r = 0.11). In contrast, spike number and 1000-grain weight were weakly negatively correlated (r = -0.15). Furthermore, a single nucleotide polymorphism (SNP) marker for the HSP16.9 gene was utilized to assess heat tolerance in 19 wheat lines. All lines produced a single band of 197 bp, indicating a lack of allelic polymorphism at this locus among the evaluated genotypes. Furthermore, three gene-specific primers targeting Vrn genes (Vrn-A1b, Vrn-B1a, and Vrn-B1b) were used to characterize 19 wheat lines. All lines carried the dominant Vrn-A1b allele (147 bp), using primer Vrn-p2, indicating a spring growth habit and the ability to flower without a prolonged cold requirement. At the Vrn-B1a locus, 15 lines possessed the Vrn-B1a allele (709 bp), using primer Vrn-P5. Using the co-dominant marker Vrn-P7, one line (L10) exhibited the Vrn-B1a allele (215 bp), while 15 lines showed the dominant Vrn-B1b allele (252 bp). In addition, three lines (L5, L8, and L17) were heterozygous, displaying both 215 and 252 bp fragments. On the other hand, Jaccard’s genetic distance (GD) coefficient was employed to evaluate the genetic divergence among 19 wheat lines based on SCoT loci. The GD values ranged from 0.62 to 0.97. Therefore, the specific wheat genotypes possess valuable germplasm characteristics, making them excellent candidates for breeding programs focused on increasing grain yield and developing new, high-performing wheat varieties.

Exploring Qualitative and Quantitative Genetic Variations of Barley (Hordeum vulgare L.) Genotypes Grown under Heat Stress Conditions

: Heat stress is a major abiotic constraint limiting barley ( Hordeum vulgare L.) productivity in regions experiencing rising temperatures. This study evaluated the genetic variability and morphophysiological as well as yield responses of 50 barley genotypes under control and heat-stressed conditions to identify superior lines for thermotolerance breeding. A completely randomized design (CRD) with replications was used, and data was collected for ten morpho-physiological and yield traits. Analysis of variance (ANOVA) indicated highly significant ( p ≤ 0.001) effects of genotype, treatment, and their interaction on most of the measured traits. Wide phenotypic variation was observed for grain yield (1.62–9.60 g plant − 1 ) and thousand-grain weight (19.18–40.02 g). High genotypic and phenotypic coefficients of variation, heritability, and genetic advance for grain yield plant − 1 , total biomass accumulation plant − 1 , and leaf area plant − 1 indicated strong additive genetic control. Correlation and network analyses showed strong positive associations among plant height, total biomass accumulation plant − 1 , chlorophyll content, leaf area plant − 1 , thousand-grain weight, and grain yield plant − 1 . Heatmap clustering and the multi-trait genotype-ideotype distance index (MGIDI) identified BD7194, BD7188, BD8579, BD9681, and IBON14 as best heat-tolerant genotypes. Principal component analysis (PCA) revealed variation primarily driven by grain yield plant − 1 , leaf area plant − 1 , and number grains spike − 1 . Overall, these findings demonstrate substantial genetic variation for heat tolerance and identify promising genotypes that can be used as valuable resources for developing climate-resilient barley cultivars suited to heating environments.

Genetic Variability in Some Local Spring Wheat (Triticum aestivum L.) Genotypes of Bangladesh for Yield and its Attributing Traits

Purpose: Around the globe, wheat is a significant cereal crop, used for food, feed, and raw materials. The study’s main objective was to examine the diversity and variability of yield and its attributing traits among sixty (60) locally cultivated wheat genotypes of Bangladesh based on genetic analyses to formulate appropriate breeding strategies for further improvements.Research Method: A total of sixty wheat genotypes were evaluated in the field using a randomized complete block design (RCBD) with three replications to assess ten yield and yield-related parameters. Statistical analysis was conducted using R-studio software to gauge the genetic variance among these sixty wheat genotypes.Findings and Values: The analysis of variance (ANOVA) results revealed a high degree of genetic variation. The study indicated that grain production per plant exhibited the highest Genotypic coefficient of variation (GCV%) and Phenotypic coefficient of variation (PCV%), along with significant genetic advance and strong heritability. This suggests that selecting for this trait would be an efficient breeding strategy. Additionally, the number of tillers per plant, grains per spike, grains per plant, and grain yield per plant showed significant positive correlations. Shatabdi, SA-8, and PV-79 genotypes were associated with the highest yields. The work selects promising genotypes with a wide genetic diversity for yield and attributing traits, which can be used for further varietal improvement in Bangladesh.

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

SSR marker-assisted diversity in advance breeding lines of bread wheat and superior allele identification for heat tolerance

Evaluation of indigenous and exotic wheat genotypes for tolerance to severe terminal heat stress in the agro-climatic conditions of Bihar

Terminal heat stress is a major constraint limiting wheat productivity in tropical and subtropical regions. This study aimed to assess genetic diversity and identify key traits and genotypes associated with terminal heat stress tolerance using multivariate and stress-index-based approaches. A diverse panel of 500 wheat genotypes, comprising 119 indigenous and 381 exotic entries, were evaluated under three field sowing conditions (timely, late, and very late) to impose natural terminal heat stress. Data were recorded for important phenological, physiological, and yield-related traits. Principal component analysis effectively differentiated genotypes along a tolerance–susceptibility gradient under very late sown conditions. Very late sowing (VLS) imposed severe terminal heat stress, resulting in a grain yield reduction of 58.33% and 59.41% during 2022–23 and 2023–24, respectively, with an average reduction of 58.89% compared with timely sowing. Based on their ability to maintain grain yield under terminal heat stress, as reflected by low Stress susceptibility index (SSI) and Tolerance index (TOL) values and high mean productivity (MP), Stress tolerance index (STI), Grain mean productivity (GMP), Yield index (YI), and Yield stability index (YSI) values, 22 superior genotypes (13 indigenous and 9 exotic) were identified. These genotypes were further classified based on SSI. The heat-tolerant group included genotypes such as 21HTWYT-31, 40SAWSN-3160, DBW-173, PHSL-10, NEST-20-30, 40SAWSN-3080, MP-1323, NEST-20-39, and HD-2967 © . The identified genotypes and associated traits constitute valuable genetic resources for breeding wheat cultivars with enhanced terminal heat tolerance.