DBT Centre of Excellence on Brassicas, Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana, 141004, Punjab, India.
School of Agriculture and Environment and the UWA Institute of Agriculture, Faculty of Science, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.
Sci Rep. 2019 Nov 19;9(1):17089. doi: 10.1038/s41598-019-53444-3.
Sclerotinia stem rot caused by Sclerotinia sclerotiorum is a major disease of crop brassicas, with inadequate variation for resistance in primary gene pools. We utilized a wild Brassicaceae species with excellent resistance against stem rot to develop a set of B. juncea - B. fruticulosa introgression lines (ILs). These were assessed for resistance using a highly reproducible stem inoculation technique against a virulent pathogen isolate. Over 40% of ILs showed higher levels of resistance. IL-43, IL-175, IL-215, IL-223 and IL-277 were most resistant ILs over three crop seasons. Sequence reads (21x) from the three most diverse ILs were then used to create B. juncea pseudomolecules, by replacing SNPs of reference B. juncea with those of re-sequenced ILs. Genotyping by sequencing (GBS) was also carried out for 88 ILs. Resultant sequence tags were then mapped on to the B. juncea pseudomolecules, and SNP genotypes prepared for each IL. Genome wide association studies helped to map resistance responses to stem rot. A total of 13 significant loci were identified on seven B. juncea chromosomes (A01, A03, A04, A05, A08, A09 and B05). Annotation of the genomic region around identified SNPs allowed identification of 20 candidate genes belonging to major disease resistance protein families, including TIR-NBS-LRR class, Chitinase, Malectin/receptor-like protein kinase, defensin-like (DEFL), desulfoglucosinolate sulfotransferase protein and lipoxygenase. A majority of the significant SNPs could be validated using whole genome sequences (21x) from five advanced generation lines being bred for Sclerotinia resistance as compared to three susceptible B. juncea germplasm lines. Our findings not only provide critical new understanding of the defensive pathway of B. fruticulosa resistance, but will also enable development of marker candidates for assisted transfer of introgressed resistant loci in to agronomically superior cultivars of crop Brassica.
由核盘菌引起的菌核病是作物芸薹属的主要病害，其初级基因库中对该病害的抗性变化不足。我们利用一种野生芸薹属植物，其对菌核病具有极好的抗性，开发了一系列芥菜-短梗芥渐渗系（ILs）。利用一种对强毒病原体分离物具有高度重现性的茎接种技术，对这些渐渗系进行了抗性评估。超过 40%的 ILs 表现出更高水平的抗性。在三个作物季节中，IL-43、IL-175、IL-215、IL-223 和 IL-277 是最具抗性的 ILs。然后，使用来自三个最多样化的 ILs 的 21x 序列读取来创建芥菜假分子，方法是用重测序 ILs 的 SNP 替换参考芥菜的 SNP。对 88 个 ILs 也进行了基因型测序（GBS）。然后将所得序列标签映射到芥菜假分子上，并为每个 IL 准备 SNP 基因型。全基因组关联研究有助于对抗菌核病的抗性反应进行作图。在七个芥菜染色体（A01、A03、A04、A05、A08、A09 和 B05）上共鉴定到 13 个显著位点。在鉴定 SNP 周围的基因组区域的注释允许鉴定属于主要抗病蛋白家族的 20 个候选基因，包括 TIR-NBS-LRR 类、几丁质酶、类受体样蛋白激酶、防御素样（DEFL）、脱硫葡萄糖硫转移酶蛋白和脂氧合酶。与三个易感芥菜种质系相比，使用正在为菌核病抗性培育的五个高级世代系的全基因组序列（21x）可以验证大多数显著 SNP。我们的研究结果不仅为短梗芥抗性的防御途径提供了重要的新认识，而且还将为辅助转移渐渗抗性基因座到作物芸薹属的农艺优良品种中开发标记候选基因提供依据。
