Cowpea witchweed [Striga gesnerioides (Willd.) Vatke] is a primary constraint of cowpea [Vigna unguiculata (L.) Walp.] production in West Africa. Previously, seven S. gesnerioides races were classified based upon host specificity and genotypic profiling. Because race number and distribution are dynamic systems influenced by gene flow, genetic drift, and natural selection, a thorough investigation of S. gesnerioides diversity and the effectiveness of known sources of resistance in cowpea is needed to develop varieties with durable and broad-spectrum Striga resistance. In this study, we screened seven cowpea lines against 58 unique S. gesnerioides populations collected from across nine West African countries. Individuals from 10 S. gesnerioides populations were genotyped with simple sequence repeat (SSR) markers. We identified six races of S. gesnerioides based on their parasitism of the seven cowpea lines with known differential resistance genotypes. No cowpea line was resistant to all 58 Striga populations and none of the Striga populations were able to overcome the resistance of all seven lines. A novel race, SG6, of the parasite collected from Kudu, Nigeria, was found to overcome more cowpea resistance genes than any previously reported race. SSR analysis indicates that Striga populations are highly differentiated and genetic relatedness generally corresponds with geographic proximity rather than their host compatibility. Due to the dearth of broad-spectrum resistance found among Striga-resistant cowpea lines, there exists a need to stack multiple Striga resistance genes in order to confer broad-spectrum and durable resistance.

中文翻译：

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西非豇豆金缕梅（Striga gesnerioides）的种系结构及其对豇豆独脚金抗性育种的启示

豇豆金缕梅[桔梗(Willd.) Vatke] 是豇豆 [豇豆(L.) Walp.] 在西非的生产。此前，七苦苣苔根据宿主特异性和基因型谱对种族进行分类。由于种族数量和分布是受基因流动、遗传漂变和自然选择影响的动态系统，因此对苦苣苔开发具有持久性和广谱性的品种需要豇豆的多样性和已知抗性来源的有效性独脚金反抗。在这项研究中，我们针对 58 个独特的豇豆品系筛选了 7 个豇豆品系苦苣苔从九个西非国家收集的人口。10 岁以下的个人苦苣苔使用简单序列重复（SSR）标记对种群进行基因分型。我们确定了六个种族苦苣苔基于它们对具有已知差异抗性基因型的七种豇豆品系的寄生。没有豇豆品系对所有 58独脚金人口和没有独脚金种群能够克服所有七个系的抗性。发现从尼日利亚 Kudu 收集的寄生虫的新种族 SG6 比以前报道的任何种族都克服了更多的豇豆抗性基因。SSR 分析表明独脚金种群高度分化，遗传相关性通常与地理接近度而不是它们的宿主兼容性相对应。由于缺乏广谱耐药性独脚金-抗性豇豆系，需要堆叠多个独脚金抗性基因，以赋予广谱和持久的抗性。