Heavy metal pollution is considered to be a major constraint of the ecosystem in current times. Heavy metals present in the earth’s crust naturally. The intoxication emerges when they are accumulated above the threshold into the environment via natural and/or anthropogenic activities, modern industrialization and some agricultural practices. Large areas of land have been polluted with heavy metals owing to the extensive application of pesticides, fertilizers, municipal and compost wastes, and also due to heavy metal release from smelting industries and metalliferous mines. Heavy metals potentially affect plant growth, metabolism and ionic status. Modification of the oxidative status of the cells is the predominant effect of heavy metals via excessive reactive oxygen species (ROS). Moreover, once inside the cells, heavy metals deregulate the defense components and homeostasis between the production of ROS and

Wheat is an important source of dietary protein and daily calories for majority of the world’s population. Although several pests and diseases affect yield potential and quality, the three rusts and powdery mildew fungi have caused major epidemics in the past and continue to threaten wheat production despite the widespread use of genetic resistance and fungicides. The evolution and migration of more virulent and aggressive race lineages of rust fungi have rendered varieties vulnerable. Fusarium head blight, leaf spotting diseases, root diseases and, more recently, wheat blast (in South America, Bangladesh and more recently Zambia) have become increasingly important owing to narrow options for resistance diversity. Race-specific and quantitative resistance are well studied for most diseases; their selection and deployment as combinations through phenotyping coupled with molecular strategies offer grea

Wheat stripe rust (caused by Puccinia striiformis f. sp. tritici) is a major disease that damages wheat plants and affects wheat yield all over the world. In recent years, stripe rust became a major problem that affects wheat yield in Egypt. New races appeared and caused breakdowns in the resistant genotypes. To improve resistance in the Egyptian genotypes, new sources of resistance are urgently needed. In the recent research, a set of 95 wheat genotypes collected from 19 countries, including Egypt, were evaluated for their resistance against the Egyptian race(s) of stripe rust under field conditions in the two growing seasons 2018/2019 and 2019/2020. A high genetic variation was found among the tested genotypes. Single marker analysis was conducted using a subset of 71 genotypes and 424 diversity array technology (DArT) markers, well distributed across the genome. Out of the tested markers, 13 stable markers were identified that were significantly associated with resistance in both years (p-value ≤ 0.05). By using the sequence of the DArT markers, the chromosomal position of the significant DArT markers was detected, and nearby gene models were identified. Two markers on chromosomes 5A and 5B were found to be located within gene models functionally annotated with disease resistance in plants. These two markers could be used in marker-assisted selection for stripe rust resistance under Egyptian conditions. Two German genotypes were carrying the targeted allele of all the significant DArT markers associated with stripe rust resistance and could be used to improve resistance under Egyptian conditions.

Wheat is a key economically important cereal crop that is consumed globally. While the grain yield increase is steady at around 1%, it is not enough to meet the growing global demands of the next decades. One the major factor that affects wheat production is the uncertainty in climatic patterns. High temperature, drought, frost, and salinity are some of the abiotic stresses known to affect wheat production significantly. Developing wheat varieties with stable and high grain yield is the crucial for sustainable wheat production. Though, diversity for tolerance to abiotic stress exists within the wheat gene pools and elite germplasms, there is a need to rapidly introgress and breed for stress adapted lines. Optimization of the breeding process, through use of effective screening technologies, faster generation advance, and recycling of parents could impact the varietal development process significantly. The advances in

Abstract

Background and aims

Pb and Sn concentration increase rapidly due to the industrial revolution and cause a significant reduction in wheat production and productivity. Understanding the genetic control of Pb and Sn tolerance is very important to produce wheat cultivars that are tolerant to such metals.

Methods

Extensive genetic analyses using genome-wide association study, functional annotation, and gene enrichment were investigated in a set of 103 highly diverse spring wheat genotypes. Kernel traits such as kernel length (KL), kernel diameter (KD), kernel width (KW), and 1000-kernel weight (TKW) were measured under each metal as well as under controlled conditions.

Results

The GWAS identified a total of 131, 126, and 115 markers that were associated with kernel traits under Ctrl, Pb, and Sn. Moreover, the stress tolerance index (STI) for Pb and Sn was calculated and GWAS revealed 153 and 105 significant markers, respectively. Remarkably, one SNP Ku_c269_2643 located within TraesCS2A02G080700 gene model was found to be associated with KL under the three conditions. The results of gene enrichment revealed three, three, and six gene networks that have an association with the processes involved in kernel formation. The target alleles of all significant markers detected by GWAS were investigated in the most tolerant wheat genotypes to truly select the candidate parents for crossing in future breeding programs.

Conclusion

This is the first study that unlocked the genetic control of kernel yield under controlled and heavy metals conditions. Understanding the genetic control of kernel traits under heavy metals will accelerate breeding programs to improve wheat tolerance to Pb and Sn.