Genomic regions associated with heat stress tolerance in tropical maize (Zea mays L.)

Abstract

With progressive climate change and the associated increase in mean temperature, heat stress tolerance has emerged as one of the key traits in the product profile of the maize breeding pipeline for lowland tropics. The present study aims to identify the genomic regions associated with heat stress tolerance in tropical maize. An association mapping panel, called the heat tolerant association mapping (HTAM) panel, was constituted by involving a total of 543 tropical maize inbred lines from diverse genetic backgrounds, test-crossed and phenotyped across nine locations in South Asia under natural heat stress. The panel was genotyped using a genotyping-by-sequencing (GBS) platform. Considering the large variations in vapor pressure deficit (VPD) at high temperature (Tmax) across different phenotyping locations, genome-wide association study (GWAS) was conducted separately for each location. The individual location GWAS identified a total of 269 novel significant single nucleotide polymorphisms (SNPs) for grain yield under heat stress at a p value of < 10–5. A total of 175 SNPs were found in 140 unique gene models implicated in various biological pathway responses to different abiotic stresses. Haplotype trend regression (HTR) analysis of the significant SNPs identified 26 haplotype blocks and 96 single SNP variants significant across one to five locations. The genomic regions identified based on GWAS and HTR analysis considering genomic region x environment interactions are useful for breeding efforts aimed at developing heat stress resilient maize cultivars for current and future climatic conditions through marker-assisted introgression into elite genetic backgrounds and/or genome-wide selection.

Association analysis for agronomic traits in wheat under terminal heat stress

“…Each significant MTA was identifiend on 1A , 6A and 2B for flag leaf area, spikelet per spike and biomass per plant respectively whereas, only two MTAs were identified on 1A and 7D under heat stress conditions. MTAs for different agronomic traits on 3A , 4A , 6A , 1B , 2B , 2D and 6D were previously reported normal conditions ( Sharma et al, 2021 , Seetharam et al, 2021 , Gupta et al, 2015 , Ain et al, 2015 , Zhao et al, 2015 ) that was different from markers identified and grwoing conditions in current study. In summary, few markers associated with traits were identified previously on same chromosomes under normal conditions, although heat stress conditions investigated in present study was different from previous studies.…”

“…Higher the average allelic frequency and PIC value indicates the higher genetic diversity. Current study revealed the allelic frequency and PIC values on individual genome as well as each chromosome of wheat ( Sharma et al, 2021 , Seetharam et al, 2021 ). However, allele frequency and PIC values were observed from lowest to highest D < B < A genome that indicated lowest genetic diversity on D and B genome of wheat as compared to A genome in Pakistani post-green revolution varieties and CIMMYT lines…”

“…Marker trait associaion application is promising approach in plant breeding to deal with the limitations faced in linkage mapping ( Sharma et al, 2021 , Seetharam et al, 2021 , Kraakman et al, 2004 ). It improves the efficiency and precision of indirect selection of thermotolerance traits in breeding programs.…”

The Influence of Parental Heat-Stress Priming on Drought-Tolerant Maize Progenies’ Field Performance

“…Heat stress slows crop growth and may cause a shift in phenological development, resulting in a yield loss in maize [19]. Heat stress caused various reactions in maize plants in different regions [20]. This finding highlights the importance of including heat stress tolerance in maize cultivar development [20].…”

“…Heat stress caused various reactions in maize plants in different regions [20]. This finding highlights the importance of including heat stress tolerance in maize cultivar development [20]. It has been demonstrated that the response of maize plants to a single stressor differs from the synergistic effect of multiple stressors [3,4].…”