Ahmed Zubair, Khalid Maria, Ghafoor Abdul, Shah Muhammad Kausar Nawaz, Raja Ghazala Kaukab, Rana Rashid Mehmood, Mahmood Tahir, Thompson Addie M
Department of Plant Breeding and Genetics, Pir Mehar Ali Shah Arid Agriculture University, Rawalpindi, Pakistan.
Crop Disease Research Institute, National Agricultural Research Center (Pakistan), Islamabad, Pakistan.
Front Genet. 2022 Mar 16;13:819849. doi: 10.3389/fgene.2022.819849. eCollection 2022.
Global environmental changes with more extreme episodes of heat waves are major threats to agricultural productivity. Heat stress in spring affects the reproductive stage of maize, resulting in tassel blast, pollen abortion, poor pollination, reduced seed set, barren ears and ultimately yield loss. As an aneamophelous crop, maize has a propensity for pollen abortion under heat stress conditions. To overcome the existing challenges of heat stress and pollen abortion, this study utilized a broad genetic base of maize germplasm to identify superior alleles to be utilized in breeding programs. A panel of 375 inbred lines was morpho-physiologically screened under normal and heat stress conditions in two locations across two consecutive planting seasons, 2017 and 2018. The exposure of pollen to high temperature showed drastic decline in pollen germination percentage. The average pollen germination percentage (PGP) at 35 and 45°C was 40.3% and 9.7%, respectively, an average decline of 30.6%. A subset of 275 inbred lines were sequenced using tunable genotyping by sequencing, resulting in 170,098 single nucleotide polymorphisms (SNPs) after filtration. Genome wide association of PGP in a subset of 122 inbred lines resulted in ten SNPs associated with PGP35°C ( ≤ 10), nine with PGP45°C ( ≤ 10-10) and ten SNPs associated with PGP ratio ( ≤ 10). No SNPs were found to be in common across PGP traits. The number of favorable alleles possessed by each inbred line for PGP35°C, PGP45°C, and the PGP ratio ranged between 4 and 10, 3-13 and 5-13, respectively. In contrast, the number of negative alleles for these traits ranged between 2 and 8, 3-13 and 3-13, respectively. Genetic mapping of yield (adjusted weight per plant, AWP) and flowering time (anthesis-silking interval, ASI) in 275 lines revealed five common SNPs: three shared for AWP between normal and heat stress conditions, one for ASI between conditions, and one SNP, CM007648.1-86615409, was associated with both ASI and AWP. Variety selection can be performed based on these favorable alleles for various traits. These marker trait associations identified in the diversity panel can be utilized in breeding programs to improve heat stress tolerance in maize.
全球环境变化伴随着更极端的热浪事件，这是农业生产力面临的主要威胁。春季的热应激会影响玉米的生殖阶段，导致雄穗枯萎、花粉败育、授粉不良、结实率降低、果穗空瘪，最终造成产量损失。作为一种风媒作物，玉米在热应激条件下容易出现花粉败育。为了克服热应激和花粉败育的现有挑战，本研究利用了广泛的玉米种质遗传基础来鉴定可用于育种计划的优良等位基因。在2017年和2018年连续两个种植季节，在两个地点对一组375个自交系进行了正常和热应激条件下的形态生理筛选。花粉暴露于高温下，花粉萌发率急剧下降。在35℃和45℃时的平均花粉萌发率分别为40.3%和9.7%，平均下降了30.6%。使用可调测序基因分型对275个自交系的一个子集进行测序，过滤后得到170,098个单核苷酸多态性（SNP）。对122个自交系子集中的花粉萌发率进行全基因组关联分析，结果发现10个与35℃花粉萌发率相关的SNP（≤10），9个与45℃花粉萌发率相关的SNP（≤10 - 10），以及10个与花粉萌发率比值相关的SNP（≤10）。在不同花粉萌发率性状中未发现共同的SNP。每个自交系在35℃花粉萌发率、45℃花粉萌发率和花粉萌发率比值方面拥有的有利等位基因数量分别在4至10个、3至13个和5至13个之间。相比之下，这些性状的负等位基因数量分别在2至8个、3至13个和3至13个之间。对275个品系的产量（单株调整重量，AWP）和开花时间（抽雄 - 吐丝间隔，ASI）进行遗传图谱分析，发现了5个共同的SNP：3个在正常和热应激条件下的AWP中共享，1个在不同条件下的ASI中共享，还有1个SNP，CM007648.1 - 86615409，与ASI和AWP都相关。可以根据这些不同性状的有利等位基因进行品种选择。在多样性群体中鉴定出的这些标记 -性状关联可用于育种计划，以提高玉米的热应激耐受性。
