Instituto de Biotecnología, Centro de Investigaciones en Ciencias Veterinarias y Agronómicas (CICVyA), Instituto Nacional de Tecnología Agropecuaria (INTA); Instituto de Agrobiotecnología y Biología Molecular (IABIMO), INTA-CONICET Nicolas Repetto y Los Reseros s/n (1686), Hurlingham, Buenos Aires, Argentina.
Consejo Nacional de Investigaciones Científicas y Técnicas-CONICET, Ciudad Autónoma de Buenos Aires, Argentina.
BMC Plant Biol. 2020 Jul 8;20(1):322. doi: 10.1186/s12870-020-02529-7.
Sclerotinia sclerotiorum is a necrotrophic fungus that causes Sclerotinia head rot (SHR) in sunflower, with epidemics leading to severe yield losses. In this work, we present an association mapping (AM) approach to investigate the genetic basis of natural resistance to SHR in cultivated sunflower, the fourth most widely grown oilseed crop in the world.
Our association mapping population (AMP), which comprises 135 inbred breeding lines (ILs), was genotyped using 27 candidate genes, a panel of 9 Simple Sequence Repeat (SSR) markers previously associated with SHR resistance via bi-parental mapping, and a set of 384 SNPs located in genes with molecular functions related to stress responses. Moreover, given the complexity of the trait, we evaluated four disease descriptors (i.e, disease incidence, disease severity, area under the disease progress curve for disease incidence, and incubation period). As a result, this work constitutes the most exhaustive AM study of disease resistance in sunflower performed to date. Mixed linear models accounting for population structure and kinship relatedness were used for the statistical analysis of phenotype-genotype associations, allowing the identification of 13 markers associated with disease reduction. The number of favourable alleles was negatively correlated to disease incidence, disease severity and area under the disease progress curve for disease incidence, whereas it was positevily correlated to the incubation period.
Four of the markers identified here as associated with SHR resistance (HA1848, HaCOI_1, G33 and G34) validate previous research, while other four novel markers (SNP117, SNP136, SNP44, SNP128) were consistently associated with SHR resistance, emerging as promising candidates for marker-assisted breeding. From the germplasm point of view, the five ILs carrying the largest combination of resistance alleles provide a valuable resource for sunflower breeding programs worldwide.
核盘菌是一种坏死型真菌，可引起向日葵的核盘菌茎腐病（SHR），该病的流行会导致严重的产量损失。在这项工作中，我们提出了一种关联作图（AM）方法来研究栽培向日葵对 SHR 天然抗性的遗传基础，向日葵是世界上第四大广泛种植的油料作物。
我们的关联作图群体（AMP）由 135 个自交系（ILs）组成，使用 27 个候选基因、一组 9 个与 SHR 抗性相关的简单重复序列（SSR）标记、以及一组 384 个位于与应激反应相关的分子功能基因的 SNP 进行了基因分型。此外，考虑到该性状的复杂性，我们评估了四个疾病描述符（即疾病发病率、疾病严重度、疾病发病率的疾病进展曲线下面积和潜伏期）。因此，这项工作是迄今为止对向日葵抗病性进行的最详尽的 AM 研究。混合线性模型考虑了群体结构和亲缘关系，用于表型-基因型关联的统计分析，允许鉴定出 13 个与疾病减少相关的标记。有利等位基因的数量与疾病发病率、疾病严重度和疾病发病率的疾病进展曲线下面积呈负相关，而与潜伏期呈正相关。
这里鉴定的与 SHR 抗性相关的 4 个标记（HA1848、HaCOI_1、G33 和 G34）验证了先前的研究，而另外 4 个新标记（SNP117、SNP136、SNP44、SNP128）与 SHR 抗性一致相关，成为标记辅助育种的有前途的候选标记。从种质资源的角度来看，携带最大抗性等位基因组合的 5 个 IL 为全世界的向日葵育种计划提供了宝贵的资源。
