Mapping Qtl For Heat Tolerance Component Traits In Triticum Durum Desf. X Aegilops Speltoides Tausch. Backcross Introgression Lines And Transfer To Triticum Aestivum L.
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Date
2023
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Punjab Agricultural University
Abstract
Wheat, a major cereal crop, is the most consumed staple after rice in India. Frequent episodes of heat waves during the past decade have raised concerns about food security and necessitates the development of heat-tolerant wheat cultivars. A mapping population comprising 315 BC2F10 backcross introgression lines (BILs) was developed by crossing Triticum durum cultivar PDW274 and heat tolerant diploid wild relative Aegilops speltoides accession pau3809 to map QTLs for terminal heat tolerance. The homozygous BILs were evaluated for heat stress tolerance component traits under an optimum environment (OE) and a heat-stressed environment (HE) for the two cropping seasons 2017-18 and 2018-19. Data on spike length, spikelet number per spike, peduncle length, thousand-grain weight, grains per spike, days to heading, days to maturity, grain filling duration, NDVI at heading and plot yield were recorded. Heat tolerance index was calculated for all the traits except plant height and used for QTL mapping. Genotyping-by-sequencing (GBS) of the BILs was carried out, and 3085 polymorphic SNPs were obtained. The QTL mapping for heat tolerance traits detected fifty QTLs on all the chromosomes except 7B. The PVE of the mapped QTLs ranged from 5% to 11.5%, indicating the minor effect contributed by the QTLs on the total phenotypic variability. Several candidate genes reported to play a role in heat stress responses were identified by browsing the 1 Mb physical region flanking the stable QTLs detected under the HE. To introgress the heat tolerance QTLs, three BILs, DS201, DS394 and DS437, which were superior for one or more phenotypic traits, were crossed with the popular bread wheat cultivars PBW723 and PBW725 along with an advanced breeding line CB762 (= PBW550+GpcB1+Yr5). Kompetitive allele-specific PCR (KASP) markers were designed based on the mapped SNPs for targeting the QTLs associated with heat tolerance traits. But these markers failed to differentiate between the donor BILs and the bread wheat parents, making them unfit for marker-assisted selection. Therefore, phenotypic selections were carried out from the BC2F2 generation onwards to select promising lines for important heat tolerance traits. Nineteen BC2F3 lines were selected that performed better than the respective bread wheat parents for one or more of the heat tolerance-associated traits. The selected BC2F3 lines can be advanced further and screened for heat tolerance at multiple locations. A well-developed root system is essential for efficient nutrient and water uptake. The BILs were evaluated for various root architecture traits during the 2019-20 and 2020-21 cropping seasons. The roots were sampled at the maximum tillering stage and data on various root architecture traits namely, total root length, root surface area, root projected area, root volume, average root diameter, number of root tips, number of root forks, number of root crossings and root dry weight were recorded. The QTL mapping for root architecture traits detected twenty-one QTLs for various root architecture traits on chromosomes 1A, 2A, 2B, 3B, 5A and 6B. Scanning of the 1Mb region flanking the mapped SNPs linked to the stable QTLs revealed multiple genes involved in root growth and development. These QTLs can be used in breeding programmes after the development and validation of suitable marker assays.
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Navaneetha Krishnan J (2023). Mapping Qtl For Heat Tolerance Component Traits In Triticum Durum Desf. X Aegilops Speltoides Tausch. Backcross Introgression Lines And Transfer To Triticum Aestivum L. (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.