Longmei Ningthaipuilu, Gill Gurjit Kaur, Zaidi Pervez Haider, Kumar Ramesh, Nair Sudha Krishnan, Hindu Vermuri, Vinayan Madhumal Thayil, Vikal Yogesh
Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana, Punjab, India.
International Maize and Wheat Improvement Centre (CIMMYT), Asia Regional Office, Hyderabad, India.
BMC Genomics. 2021 Mar 4;22(1):154. doi: 10.1186/s12864-021-07463-y.
Heat tolerance is becoming increasingly important where maize is grown under spring season in India which coincide with grain filling stage of crop resulting in tassel blast, reduced pollen viability, pollination failure and barren ears that causes devastating yield losses. So, there is need to identify the genomic regions associated with heat tolerance component traits which could be further employed in maize breeding program.
An association mapping panel, consisting of 662 doubled haploid (DH) lines, was evaluated for yield contributing traits under normal and natural heat stress conditions. Genome wide association studies (GWAS) carried out using 187,000 SNPs and 130 SNPs significantly associated for grain yield (GY), days to 50% anthesis (AD), days to 50% silking (SD), anthesis-silking interval (ASI), plant height (PH), ear height (EH) and ear position (EPO) were identified under normal conditions. A total of 46 SNPs strongly associated with GY, ASI, EH and EPO were detected under heat stress conditions. Fifteen of the SNPs was found to have common association with more than one trait such as two SNPs viz. S10_1,905,273 and S10_1,905,274 showed colocalization with GY, PH and EH whereas S10_7,132,845 SNP associated with GY, AD and SD under normal conditions. No such colocalization of SNP markers with multiple traits was observed under heat stress conditions. Haplotypes trend regression analysis revealed 122 and 85 haplotype blocks, out of which, 20 and 6 haplotype blocks were associated with more than one trait under normal and heat stress conditions, respectively. Based on SNP association and haplotype mapping, nine and seven candidate genes were identified respectively, which belongs to different gene models having different biological functions in stress biology.
The present study identified significant SNPs and haplotype blocks associated with yield contributing traits that help in selection of donor lines with favorable alleles for multiple traits. These results provided insights of genetics of heat stress tolerance. The genomic regions detected in the present study need further validation before being applied in the breeding pipelines.
在印度春季种植玉米的地区，耐热性变得越来越重要，因为这与作物的灌浆期相吻合，会导致雄穗枯萎、花粉活力降低、授粉失败和空穗，从而造成毁灭性的产量损失。因此，需要鉴定与耐热性组成性状相关的基因组区域，以便在玉米育种计划中进一步应用。
对一个由662个双单倍体（DH）系组成的关联作图群体，在正常和自然热胁迫条件下对产量构成性状进行了评估。利用187,000个单核苷酸多态性（SNP）进行全基因组关联研究（GWAS），在正常条件下鉴定出130个与籽粒产量（GY）、50%抽雄天数（AD）、50%吐丝天数（SD）、抽雄-吐丝间隔（ASI）、株高（PH）、穗位高（EH）和穗位（EPO）显著相关的SNP。在热胁迫条件下，共检测到46个与GY、ASI、EH和EPO强烈相关的SNP。发现其中15个SNP与多个性状存在共同关联，例如两个SNP即S10_1,905,273和S10_1,905,274与GY、PH和EH共定位，而S10_7,132,845 SNP在正常条件下与GY、AD和SD相关。在热胁迫条件下未观察到SNP标记与多个性状的这种共定位。单倍型趋势回归分析分别揭示了122个和85个单倍型块，其中，在正常和热胁迫条件下分别有20个和6个单倍型块与多个性状相关。基于SNP关联和单倍型作图，分别鉴定出9个和7个候选基因，它们属于在胁迫生物学中具有不同生物学功能的不同基因模型。
本研究鉴定出与产量构成性状相关的显著SNP和单倍型块，有助于选择具有多个性状有利等位基因的供体系。这些结果提供了耐热胁迫遗传学的见解。本研究中检测到的基因组区域在应用于育种流程之前需要进一步验证。
