The common bean (Phaseolus vulgaris) is a high protein crop and the main legume in the cropping system of western Kenya. Despite its importance, common bean yields are low (<1.0 t/ha) and declining. Bean common mosaic virus (BCMV) and bean common mosaic necrosis virus (BCMNV) are the most common and most destructive viruses and can cause a yield loss as high as 100%. In Kenya, a limited number of cultivars and exotic genotypes with resistance to BCMV and BCMNV strains have been reported. This study sought to determine the distribution and screen popular cultivars for resistance to the viruses. In October 2016 and May 2017, two diagnostic surveys for bean common mosaic disease (BCMD) were conducted in seven counties of western Kenya namely Bungoma, Busia, Homa Bay, Nandi, Vihiga, Kakamega and Siaya. Leaf samples showing virus‐like symptoms were collected and analysed by ELISA. Sixteen popularly grown bean cultivars together with cowpea (Vigna unguiculata), soybean (Glycine max), green grams (Vigna radiata) and groundnut (Arachis hypogaea) were planted in a greenhouse in a completely randomized block design with three replicates. The plants were inoculated with BCMNV isolate at 3‐leaf stage. Data were taken weekly for 3 weeks on type of symptoms expressed and number of plants infected. In total, 270 bean farms were visited. Symptoms of mosaic, downward curling, local lesions, stunting or a combination of these were observed during both surveys. Mean virus incidence was higher in the short rain season (50.2%) than in the long rain season (35.6%). The mean BCMD severity on a scale of 0–3 was highest (2.3) in Kakamega County and lowest (0.5) in Siaya. On variety resistance tests to BCMNV isolate, 10 bean cultivars were susceptible, four tolerant and two resistant. BCMNV is widely distributed across counties probably because of use of uncertified seeds by farmers and inoculum pressure from seed and aphid vector. For improved yields of common bean, farmers should be advised to plant certified seeds for all legumes in the cropping system.

中文翻译：

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肯尼亚西部豆类常见花叶病的发病率和严重程度以及流行的豆类品种对该病的抵抗力

普通豆（Phaseolus vulgaris）是一种高蛋白作物，是肯尼亚西部种植系统中的主要豆科植物。尽管它很重要，但普通豆类的产量很低（<1.0 吨/公顷）并且还在下降。豆类普通花叶病毒 (BCMV) 和豆类普通花叶坏死病毒 (BCMNV) 是最常见和最具破坏性的病毒，可造成高达 100% 的产量损失。在肯尼亚，已经报道了对 BCMV 和 BCMNV 菌株具有抗性的数量有限的栽培品种和外来基因型。该研究试图确定流行品种的分布并筛选对病毒的抗性。2016 年 10 月和 2017 年 5 月，在肯尼亚西部的七个县，即班戈马、布西亚、霍马湾、南迪、维希加、卡卡梅加和西亚亚，对豆类常见花叶病（BCMD）进行了两次诊断调查。收集显示病毒样症状的叶样本并通过 ELISA 进行分析。将十六个普遍种植的豆类品种与豇豆 (Vigna unguiculata)、大豆 (Glycine max)、绿豆 (Vigna radiata) 和落花生 (Arachis hypogaea) 一起种植在温室中，采用完全随机的区组设计，三个重复。在 3 叶期用 BCMNV 分离株接种植物。在 3 周内每周采集有关表现的症状类型和感染植物数量的数据。总共访问了 270 个豆类农场。在两次调查中都观察到马赛克、向下卷曲、局部病变、发育迟缓或这些症状的组合。短雨季（50.2%）的平均病毒发病率高于长雨季（35.6%）。卡卡梅加县 0-3 级的平均 BCMD 严重程度最高 (2.3)，最低 (0. 5）在西亚。在对 BCMNV 分离株的抗性试验中，10 个豆类品种敏感，4 个耐受，2 个抗性。BCMNV 广泛分布于各县，可能是因为农民使用未经认证的种子以及种子和蚜虫载体的接种压力。为了提高普通豆的产量，应建议农民在种植系统中为所有豆类种植经过认证的种子。