Lohithaswa H C, Balasundara D C, Mallikarjuna M G, Sowmya M S, Mallikarjuna N, Kulkarni R S, Pandravada Anand S, Bhatia Bhupendra S
Department of Genetics and Plant Breeding, University of Agricultural Sciences, GKVK, Bangalore, 560 065, Karnataka, India.
Corteva Agriscience Pvt. Ltd, Kallinayakanahalli, 561 213, Gauribidanur, Chikkaballapur, Karnataka, India.
J Appl Genet. 2024 Oct 24. doi: 10.1007/s13353-024-00911-x.
Northern corn leaf blight (NLB) caused by Setosphaeria turcica (Luttrell) Leonard & Suggs is a severe foliar disease in maize. Resistance to NLB is complexly inherited and controlled by several quantitative trait loci (QTL) distributed across the genome. Phenotype and DNA marker-based selection for resistance to NLB is expected to be effective. Hence, an investigation was carried out to predict the genetic value of selection candidates for resistance to NLB and compare the accuracies of genomic prediction in two F populations of two crosses (CM212 × MAI172; CM202 × SKV50) derived from contrasting parents. Linkage analysis using 297 polymorphic SNPs in population-1 and 290 polymorphic SNPs in population-2 revealed ten linkage groups spanning 3623.88 cM and 4261.92 cM with an average distance of 12.40 cM and 14.9 cM in population-1 and population-2, respectively. Location-wise and pooled data across locations identified common QTLs on linkage groups 1 and 6 in population-1 and 3 and 8 in population-2. The prediction accuracy of the QTL mapping (9.92 and 9.10 for population-1 and population-2, respectively) was based on only a few markers, which explained higher percent phenotypic variation. The prediction accuracies of the genomic estimated breeding values in the present investigation were relatively low in population-1 (0.24 to 0.26) and population-2 (0.29-0.32) compared to the expected accuracies. This could be due to fewer polymorphic markers and a small training/population size. Though the GS prediction accuracies were relatively low, they were significantly higher than QTL mapping, which promises better genetic gain per cycle. The resistant progenies from both populations were advanced to derive inbred lines and crossed with four different testers in line × tester mating design to test for their combining ability and effectiveness of genomic selection. High overall general combining ability was exhibited by 21 inbred lines. Among Fs, 48% were assigned high overall specific combining ability status. Out of the 136 single crosses, seven recorded significant positive standard heterosis over the best check for grain yield. Twenty-five inbreds with high GEBVs were crossed with four testers to obtain 100 Fs and evaluated for their response to NLB. The majority of hybrids displayed moderate to resistant reaction to NLB either in combination with susceptible or resistant testers indicating the effectiveness of selection based on high GEBVs.
由大斑刚毛座腔菌（Setosphaeria turcica (Luttrell) Leonard & Suggs）引起的玉米大斑病是玉米上一种严重的叶部病害。对玉米大斑病的抗性是复杂遗传的，由分布在基因组中的几个数量性状位点（QTL）控制。基于表型和DNA标记的玉米大斑病抗性选择预计是有效的。因此，开展了一项研究，以预测玉米大斑病抗性选择候选材料的遗传价值，并比较来自两个杂交组合（CM212 × MAI172；CM202 × SKV50）的两个F群体中基因组预测的准确性，这两个杂交组合的亲本具有明显差异。在群体1中使用297个多态性单核苷酸多态性（SNP）以及在群体2中使用290个多态性SNP进行连锁分析，分别在群体1和群体2中揭示了10个连锁群，跨度分别为3623.88厘摩（cM）和4261.92厘摩，平均间距分别为12.40厘摩和14.9厘摩。按位置以及跨位置汇总的数据在群体1的连锁群1和6以及群体2的连锁群3和8上鉴定出了共同的QTL。QTL定位的预测准确性（群体1和群体2分别为9.92和9.10）仅基于少数几个标记，这些标记解释了较高百分比的表型变异。与预期准确性相比，本研究中群体1（0.24至0.26）和群体2（0.29 - 0.32）中基因组估计育种值的预测准确性相对较低。这可能是由于多态性标记较少以及训练/群体规模较小。尽管基因组选择（GS）预测准确性相对较低，但它们显著高于QTL定位，这意味着每个周期有更好的遗传增益。来自两个群体的抗性后代被进一步培育以获得自交系，并在系×测验种交配设计中与四个不同的测验种杂交，以测试它们的配合力和基因组选择的有效性。21个自交系表现出较高的总体一般配合力。在F代中，48%被赋予较高的总体特殊配合力状态。在136个单交种中，有7个在籽粒产量方面比最佳对照表现出显著的正向标准杂种优势。将25个具有高基因组估计育种值（GEBV）的自交系与四个测验种杂交，获得100个F代，并对它们对玉米大斑病的反应进行评估。大多数杂交种在与感病或抗病测验种杂交时，对玉米大斑病表现出中度至抗性反应，这表明基于高GEBV的选择是有效的。
