【Objective】 Wheat is a cornerstone of global food security, with its production being pivotal in both China and the international community. With global climate change, the threat of high temperature has become increasingly prominent, posing a significant challenge to wheat cultivation. The strategic identification and selection of heat-tolerant germplasm, coupled with the exploration of genes associated with heat resistance, are crucial steps. These efforts are essential for broadening the genetic diversity of heat tolerance in wheat within China, providing prerequisites for breeding heat-tolerant wheat varieties and ultimately contributing to the safeguarding of our nation’s food security in the face of a warming climate. 【Method】 In this study, a natural population of 331 wheat accessions was utilized, and artificial climate chambers were employed to simulate high temperatures conditions. The heat tolerance of wheat seedlings was assessed by monitoring their survival rate under various durations of treatment, using heat resistance grade as the evaluative metric. Meanwhile, a genome-wide association study (GWAS) was conducted using the 55K SNP chip to identify genetic loci associated with heat tolerance. Expression data from multiple tissues, including roots, leaves under heat stress were analyzed, leading to the selection of genes related to heat tolerance. Subsequently, qPCR validation of candidate genes was performed using the extremely heat-tolerant accession Xinong 889 and the heat-sensitive accession Chinese Spring (CS) as materials. 【Result】 Under high-temperature stress, significant variations in survival rates were observed among different wheat accessions. The extremely heat-tolerant, moderately heat-tolerant, moderately heat-sensitive, and extremely heat-sensitive germplasm accounted for 110, 104, 110, and 7, respectively, representing 33.23%, 31.42%, 33.23%, and 2.12% of the total. Heat-tolerant germplasms, including Xinong 889, Zhengmai 7698, Zhongmai 895, Zhoumai 18, and Fengchan 3, were identified. Through GWAS, a total of 293 SNP loci significantly associated with the 12-hour survival rates (SR) and heat resistance grades (HRG) were detected, with the phenotypic variation explained ranging from 4.40% to 12.46%. Among these, 200 loci were related to the 12-hour survival rates, and 257 were related to the heat resistance grades, with 164 loci identified as the same heat-related loci. Based on significantly associated SNP markers, 313 heat-related genes were predicted. According to gene annotation information and expression data under heat stress, 23 heat tolerance candidates were selected, and after qPCR validation of differentially expressed candidate’s genes, 20 key heat tolerance candidate genes were identified. 【Conclusion】 At the seedling stage, 331 wheat germplasms were identified for heat tolerance. A rapid method was developed for determining the survival rate of wheat seedlings subjected to treatments of varying durations at 45 ℃ to assess their heat tolerance In total, 38 heat-tolerant germplasms and 293 loci significantly associated with seedling heat tolerance were screened. Also, TraesCS1A02G355900, TraesCS1A02G389500, TraesCS5A02G550700, TraesCS5D02G557100, TraesCS6D02G402500 and TraesCS7A02G232500 represented as candidate genes were filtered out.
【Objective】 The objective of this study is to develop InDel molecular markers for Island cotton, which is characterized by its superior fiber quality, particularly the fiber tensile strength-a key indicator of cotton fiber quality. The study aims to validate these markers using RIL (Recombinant Inbred Line) populations and resource materials, thereby providing a theoretical foundation for breeding new varieties of Island cotton with enhanced fiber quality. 【Method】 Utilizing a previously established population of 213 Pima S-7 and 5917 F5:6 RILs, we conducted QTL (Quantitative Trait Locus) mapping to identify the locus regulating fiber strength in Island cotton, designated qFS-chr17-1. InDel markers were designed based on whole genome sequencing (WGS) data of the parental lines, followed by the identification of polymorphic markers. Preliminary validation of these markers was performed using 40 extreme family materials selected based on phenotypic data. Genotyping was carried out on both the 213 RIL population and the 213 Island cotton resource population, alongside multi-year fiber quality data to assess the markers' effectiveness. 【Result】 The genotyping of the RIL and Island cotton resource populations with the two developed InDel markers indicated a close linkage to fiber strength phenotypic data, with significant differences observed in fiber strength traits among the differentiated materials. The analysis of genotypic combinations revealed an upward trend in fiber strength across four combination types, with materials exhibiting the Hap3 (B/A) and Hap4 (B/B) genotypes demonstrating significantly greater fiber strength than those with Hap1 (A/A) and Hap2 (A/B). Furthermore, the InDel-3L2 marker showed significant correlations with fiber length, fiber uniformity, and spinning consistency index, consistent with the observed phenotypic trends. Analysis of multi-year fiber quality data from two experimental sites revealed environmental variability in fiber quality, while temperature data indicated that the developed molecular markers are minimally influenced by environmental factors. Clustering analysis of fiber quality data from 213 Island cotton resource materials, combined with molecular marker genotyping, identified eight materials exhibiting superior fiber quality. 【Conclusion】 This study successfully developed two InDel molecular markers closely linked to the fiber strength QTL (qFS-chr17-1), which maintain their effectiveness upon combination. The InDel-3L2 marker demonstrates significant correlations with fiber length, fiber uniformity, and spinning consistency index. These markers can efficiently and accurately identify high-strength fiber resources in Island cotton, contributing to the breeding of improved fiber quality. Additionally, eight materials with excellent fiber quality have been identified.
