جستجوی مقالات مرتبط با کلیدواژه « drought tolerance » در نشریات گروه « بیوتکنولوژی و ژنتیک گیاهی »

The severe impact of drought and salinity on plant productivity presents a significant threat to worldwide food security. Plants exhibit the capacity to sense stimuli in their environment and adjust defense mechanisms through diverse regulatory networks to cope with abiotic stress. The complexities of drought and salinity tolerances can be deconstructed into contributing factors and mechanisms, classified under two categories: genetics and epigenetics. Epigenetic mechanisms play a role in partially attributing crop adaptation to the most formidable drought and salinity stresses. Plants respond to stress in part by undergoing stable alterations in gene expression, a process that involves the physical "marking" of DNA or its associated proteins, commonly called epigenetics. Plants utilize various epigenetic mechanisms to refine gene expression, vital for adaptation and phenotypic plasticity. These include DNA methylation, histone modifications, chromatin remodeling, epitranscriptomics, and gene silencing mediated by small RNAs. Notably, epigenetic modifications can be inherited or erased. Enhanced knowledge of epigenetics complements genetics and will aid in developing strategies to integrate them into crop improvement programs aimed at addressing adaptation to abiotic stress. This review highlights the latest and noteworthy findings regarding crop epigenetic responses to abiotic stress signals, particularly those pertinent to drought and salinity tolerance.

Drought is one of the main abiotic stresses limiting wheat growth and productivity worldwide. The main objective of this work was to determine population structure and marker-trait association (MTA) of 13 morpho-physiological traits of bread wheat for drought-tolerance breeding. To this end, twenty-five diverse wheat cultivars and promising lines were genotyped using AFLP. The phenotype evaluation steps of studding wheat genotypes were performed under normal and drought-stress conditions during 3 years. Low heritability estimates were obtained for spike length, heading date (DTH), and shoot biomass (24.87-28.8%) while, a high heritability was observed for the number of kernels per spike (KPS) (89.21-90.55%). The results exhibited high polymorphic level ranged from 84.62 to 100%, proving that AFLP method can be an effective tool in assessing genetic variability in any wheat breeding programs. Population structure analysis showed five subpopulations with at least 65% membership ancestry to their allocated sub-clusters, which was highly consistent with the results of cluster analysis. Mixed linear method association analysis identified 66 significant MTAs with p-values 10−06 to 10−04, justifying 7.8 to 38.7% of the phenotypic variation, observed under both environmental conditions. There were two pleiotropic markers for grain yield (GY) and KPS under normal and one pleiotropic marker for GY, thousand kernel weight (TKW) and KPS under stress conditions. The common MTAs were detected for DTH, plant height, peduncle length, and TKW under both environmental conditions. The identified linked markers with GY and its components in this study could be desirable candidate genes for future studies and marker assisted selection to develop drought-tolerant genotypes in wheat breeding programs.

For evaluating the effects of TaMOR, TaNAC69-1 and TaExpb23 expression on root system architecture and drought tolerance of wheat, 10 bread wheat varieties were compared through germination test, pot experiment and field trial. In germination test, genotypes were evaluated under 0, -3 and -6 bar osmotic potentials. In the pot experiment genotypes were compared at 50%, 75% and 100% field capacity (FC) irrigation regime. In the field trial, genotypes were grown under well-watered and rain fed conditions. Based on the results of this experiment, it was concluded that water deficit had a significant effect on all traits except for seminal root numbers. Significant genotypic differences were observed for all traits indicating the presence of genetic variability among the genotypes. Correlation coefficients showed that TaMOR gene expression had a positive correlation with plant yield under 75% FC stress (r=0.733*). TaNAC69-1 gene expression had positive correlations with plant yield and plant biomass under 50% FC (r=0.634* and r=0.711*). TaNAC69-1 gene expression also showed a positive correlation with root numbers under 50% FC condition (r=0.622*). TaNAC69-1 gene expression also showed a positive correlation with seminal root angle (r=0.648*) under severe stress. TaExpb23 expression showed positive correlation with plant yield and biomass under 75% FC (r=0.663* and r=0.723*). Based on the results of this experiment, it was concluded that under different stress levels, TaMOR, TaNAC69-1 and TaExpb23 gene expressions had significant correlations with traits. Due to significant G×E interactions, it was also concluded that the effect of expression of TaMOR, TaNAC69-1 and TaExpb23 genes on traits is different under distinct stress levels.

In order to analyze variation and find an efficient selection approach، we used crossing results between two wheat cultivars، Azar2 and 87-Zhong291. F3 plants (374 lines) and four check cultivars planted in the form of augmented experiment. For germination، seeds were irrigated once. After using multiple statistics methods such as cluster analysis، 79 different lines were selected and used for RAPD analysis with UBC3 primer that hadproduced six polymorphic bands (447 fragments in total). Jaccard''s coefficient for parents was low (0. 17). Therefore، Azar-2 and 87-Zhong291 had extreme differences with each other. For the analysis of relationship between polymorphic bands and morphological characters، logistic regression was used. The majority of characters were not related to the bands but some of morphological characters، such as biological yield، plant height، main spike weight، 1000 grain weight and peduncle length showed a negative relation with some of polymorphic bands. Among them، seed number/spike trait had a positive relationship with a 600bp band. This band could be used as a selection marker for seed number/spike trait.