Water deficit is the most severe stress factor in crop production threatening global food security. In this study, we evaluated the genetic variation in photosynthetic traits among 200 wheat cultivars evaluated under drought and rainfed conditions. Significant genotypic, treatments, and their interaction effects were detected for chlorophyll content and chlorophyll fluorescence parameters.Drought stress reduced the effective quantum yield of photosystem II (YII) from the anthesis growth stage on. Leaf chlorophyll content measured at anthesis growth stages was significantly correlated with YII and non-photochemical quenching under drought conditions, suggesting that high throughput chlorophyll content screening can serve as a good indicator of plant drought tolerance status in wheat. Breeding significantly increased the photosynthetic efficiency as newer released genotypes had higher YII and chlorophyll content than the older ones.GWAS identified a stable drought-responsive QTL on chromosome 3A for YII, while under rainfed conditions, it detected another QTL on chromosome 7A for chlorophyll content across both growing seasons. Molecular analysis revealed that the associated alleles of AX-158576783 (515.889 Mbp) on 3A co-segregates with the NADH-ubiquinone oxidoreductase (TraesCS3A02G287600) gene involved in ATP synthesis coupled electron transport and is proximal to WKRY transcription factor locus. This allele on 3A has been positively selected through breeding and has contributed to increasing the grain yield. HighlightBreeding has aided the selection of multiple pleiotropic and stable droughtresponsive alleles on chromosome 3A associated with improved photosynthetic activity and grain yield under drought stress in winter wheat.Benedict Chijioke Oyiga and Said Dadshani contributed equally to the manuscript.
Genetic diversity assessment is the principle component for conservation and characterization of germplasm. Genetic diversity study of Afghan bread wheat genotypes is a first step to identify and to select high performance genotypes and distribute to wheat breeding programs. The main objective of this study is to investigate of genetic diversity in 35 Afghan bread wheat genotypes by using Simple Sequence Repeat (SSR) and Amplified Fragment Length Polymorphism (AFLP) markers. DNA extraction according to Cetyl Trimethyl Ammonium Bromide (CTAB) method was conducted and the total genomic DNA was isolated from each variety. Sixty-four SSR primer markers were used and eighteen EcoRI+(N)/MseI+(N) primer combinations with their primer sequences were used for selective polymerase chain reaction (PCR) amplification. Every SSR and AFLP fragment was scored as present (1) or absent (0) within all genotypes under study. Marker/ Value ratio of pairwise genetic distance between genotypes according to the SSRs data was from 0.508 to 0.691 with an average distance of 0.599. Relatively different grouping pattern in comparison to AFLP data observed through cluster analysis. Both types of molecular markers (AFLP and SSR) used in this research proved to be suitable for investigating genetic diversity in the genotypes of Afghan bread wheat, however, AFLP markers gave better view of genetically relationships among genotypes than the SSR markers. The grouping generated by AFLP data showed a special agreement with the origin regions of genotypes (Ariana-07 and Mazar-99 originating from the north of Afghanistan, Lalmi-03 and Kabul-02. Large number of DNA bands identified with AFLP markers might provide a better estimation of genetic similarity than those of SSR markers.
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