School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg, 3209, South Africa.
BMC Plant Biol. 2024 Sep 19;24(1):871. doi: 10.1186/s12870-024-05590-8.
Genetic improvement for Striga hermonthica (Sh) and S. asiatica (Sa) resistance is the most economical and effective control method to enhance the productivity of maize and other major cereal crops. Hence, identification of quantitative trait loci (QTL) associated with Striga resistance and economic traits will guide the pace and precision of resistance breeding in maize. The objective of this study was to undertake a genome-wide association analysis of grain yield and Sh and Sa resistance among tropical and sub-tropical maize populations to identify putative genetic markers and genes for resistance breeding. 126 maize genotypes were evaluated under controlled environment conditions using artificial infestation of Sh and Sa. The test genotypes were profiled for grain yield (GY), Striga emergence counts at 8 (SEC8) and 10 (SEC10) weeks after planting, and Striga damage rate scores at 8 (SDR8) and 10 (SDR10) weeks after planting. Population structure analysis and genome-wide association mapping were undertaken based on 16,000 single nucleotide polymorphism (SNP) markers.
A linkage disequilibrium (LD) analysis in 798,675 marker pairs revealed that 21.52% of pairs were in significant linkage (P < 0.001). Across the chromosomes, the LD between SNPs decayed below a critical level (r = 0.1) at a map distance of 0.19 Mbp. The genome-wide association study identified 50 significant loci associated with Sh resistance and 22 significant loci linked to Sa resistance, corresponding to 39 and 19 candidate genes, respectively.
The study found non-significant QTL associated with dual resistance to the two examined Striga species Some of the detected genes reportedly conditioned insect and pathogen resistance, plant cell development, variable senescence, and pollen fertility. The markers detected in the present study for Sa resistance were reported for the first time. The gene Zm00001eb219710 was pleiotropic, and conditioned GY and SEC10, while Zm00001eb165170 affected SDR8 and SDR10, and Zm00001eb112030 conditioned SDR8 and SDR10 associated with Sh resistance. The candidate genes may facilitate simultaneous selection for Sh and Sa resistance and grain yield in maize after further validation and introgression in breeding pipelines. Overall, we recommend breeding maize specifically for resistance to each Striga species using germplasm adapted to the endemic region of each parasite.
对 Striga hermonthica (Sh) 和 S. asiatica (Sa) 抗性进行遗传改良是提高玉米和其他主要谷类作物生产力最经济有效的控制方法。因此，鉴定与 Striga 抗性和经济性状相关的数量性状位点 (QTL) 将指导玉米抗性育种的速度和精度。本研究的目的是对热带和亚热带玉米群体进行全基因组关联分析，以鉴定与 Sh 和 Sa 抗性相关的潜在遗传标记和基因，用于抗性育种。在受控环境条件下，使用 Sh 和 Sa 的人工侵染评估了 126 个玉米基因型。测试基因型的表型特征包括谷物产量 (GY)、种植后 8 周 (SEC8) 和 10 周 (SEC10) 的 Striga 出苗数，以及种植后 8 周 (SDR8) 和 10 周 (SDR10) 的 Striga 损伤率评分。基于 16000 个单核苷酸多态性 (SNP) 标记进行了群体结构分析和全基因组关联作图。
在 798675 对 SNP 中，连锁不平衡 (LD) 分析显示 21.52%的 SNP 对存在显著连锁(P<0.001)。在整个染色体上，SNP 之间的 LD 在图距为 0.19 Mbp 时低于临界水平 (r=0.1)。全基因组关联研究鉴定了 50 个与 Sh 抗性相关的显著位点和 22 个与 Sa 抗性相关的显著位点，分别对应 39 个和 19 个候选基因。
本研究发现与两种受检 Striga 物种的双重抗性相关的非显著 QTL。一些检测到的基因据称调节了昆虫和病原体的抗性、植物细胞发育、可变衰老和花粉活力。本研究中检测到的与 Sa 抗性相关的标记是首次报道。Zm00001eb219710 基因是多效的，调节 GY 和 SEC10，而 Zm00001eb165170 影响 SDR8 和 SDR10，Zm00001eb112030 调节与 Sh 抗性相关的 SDR8 和 SDR10。候选基因在经过进一步验证和导入育种管道后，可能有助于玉米同时对 Sh 和 Sa 抗性和产量进行选择。总体而言，我们建议根据每个寄生虫的流行地区，使用适应当地的种质资源，专门培育对每种 Striga 物种具有抗性的玉米。
