Global temperature is rising because of increasing concentrations of CO 2 and other greenhouse gases (e.g. methane, nitrous oxide, etc.) in the atmosphere because of the excessive use of fossil fuels. High temperature causes heat stress which reduces crop productivity. The development of heat-tolerant varieties is feasible and will help mitigate the effects of climate change. Fifty-one cotton accessions were screened in heat-stressed and non-stressed conditions in the glasshouse and field. Relative cell injury percentage (RCI %), a measure of cell membrane thermostability (CMT), was used to assess heat tolerance. Heat-tolerant accessions had more stable yield and yielded more seed cotton with better quality fibre than the heat-intolerant accessions across four environments. The responses of the 51 accessions to all four environments for the measured traits were strongly associated. RCI % of the accessions and hybrids was strongly and negatively associated with yield and fibre traits. CMT was concluded to be a useful technique for identification of heat-tolerant cotton.
The present investigation was carried out to analyse for the presence of α-amylase inhibitor gene which is responsible for resistance to rice weevil. A total of 30 simple sequence repeat (SSR) markers were used to study the genetic diversity among 30 wheat genotypes resistant to rice weevil. Among them, seventeen primers were found polymorphic on agarose gel and depicted the significant diversity among susceptible and resistant genotypes while rest thirteen primers were found monomorphic. The number of polymorphic bands per loci ranged from 1 to 3 with an average of 1.6 alleles per locus. A clear cut differentiation was exhibited among the genotypes. The average PIC value was 0.37 ranging from 0.17 (WMC120/ WMC76/WMC245) to 0.67 (WMC267), indicating diverse nature of the wheat genotypes and/or highly informative SSR markers used in this study. The analyzed wheat genotypes showed a good level of genetic variability for assessed quantitative, physio-chemical and molecular characters. Molecular markers linked with major genes for traits of interest which have been amplified by the primer set UCW108, a genic marker for GPC-B1. The range of similarity coefficient varied from 54% (PBN-51) to 74% (K 20). SAHN cluster analysis using UPGMA method separated the parental genotypes into four cluster groups, PBN 51 was positioned as single genotype in separate groups i.e., in cluster-I, K 50, K 76 and K 77 in cluster-II, K 2I and K 50 in cluster-III and K 20 in cluster-IV. In dendrogram, based on results of markers validated were able to diversify the resistant and susceptible parents, first group member PBN51 and fourth group member K20 found on the two distant groups, which were observed as most susceptible and resistant genotypes respectively, according to our controlled experiment on weevil infestation and molecular analysis done and hence, the study supports and correlates the result, obtained by these analysis. The present study also indicates that microsatellite markers able to access the genetic diversity among studied genotypes of wheat for weevil resistance.
Improvement of grain protein content (GPC), loaf volume and resistance to rusts was achieved in 11 Indian wheat cultivars that are widely grown in four different agro-climatic zones of India. This involved use of marker-assisted backcrossing (MABC) for introgression and pyramiding of the following genes: (i) the high GPC gene Gpc-B1; (ii) HMW glutenin subunits 5 + 10 at Glu-D1 loci, and (iii) rust resistance genes, Yr36, Yr15, Lr24 and Sr24. GPC was improved by 0.8–3.3%, although high GPC was generally associated with yield penalty. Further selection among high GPC lines, allowed development of progenies with higher GPC associated with improvement in 1000-grain weight and grain yield in the following four cultivars: NI5439, UP2338, UP2382 and HUW468. The high GPC progenies (derived from NI5439) were also improved for grain quality using HMW glutenin subunits 5 + 10 at Glu-D1 loci. Similarly, progenies combining high GPC and rust resistance were developed in the backgrounds of following five cultivars: Lok1, HD2967, PBW550, PBW621 and DBW1. The improved pre-bred lines developed during the present study should prove useful for development of cultivars with improved nutritional quality associated with rust resistance in future wheat breeding programmes.
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