Okul Valentor A, Ochwo-Ssemakula M, Kaweesi T, Ozimati A, Mrema E, Mwale E S, Gibson P, Achola E, Edema R, Baguma Y, Kawuki R
Makerere University, Department of Agricultural Production, P.O. Box 7062, Kampala, Uganda.
National Crops Resources Research Institute, Root Crops Program, P.O. Box 7084, Kampala, Uganda.
Crop Prot. 2018 Jun;108:39-46. doi: 10.1016/j.cropro.2018.02.008.
Cassava brown streak disease (CBSD) caused by (CBSV) and (UCBSV) is a threat to food security in sub-Saharan Africa, where the disease persistently reduces overall root quality and quantity resulting in up to 100% yield losses. Complexities in CBSD symptom expression and the damage caused on leaves, stems and roots throughout the 12 months of cassava growth require that appropriate ways of categorizing genotype response and optimal stages of evaluation be identified. This study aimed at: 1) determining plot based heritability of CBSD based on symptom expression and 2) categorizing genotype resistance to CBSD based on symptom expression. Herein, 41 genotypes were evaluated for two years at Namulonge with an additional evaluation conducted across three locations. Evaluations were done at three, six, nine and twelve months after planting. Genotype responses to CBSD varied significantly. High broad sense heritability estimates of up to 0.81 (incidence) and 0.71 (severity) were obtained. Average disease severity scores had higher broad sense heritability estimates (0.53 and 0.65) than maximum disease severity scores (0.33 and 0.61) for root and foliar severities respectively. These findings are important in choosing an appropriate evaluation method for CBSD. Genotypes displayed differing CBSD responses in type, locality and severity of symptoms. This suggested that genotypes had differences in mechanisms of resistance that can be exploited in CBSD resistance breeding.
由木薯褐色条纹病毒（CBSV）和乌干达木薯褐色条纹病毒（UCBSV）引起的木薯褐色条纹病（CBSD）对撒哈拉以南非洲的粮食安全构成威胁，在该地区，这种病害持续降低木薯的整体根质量和产量，导致高达100%的产量损失。CBSD症状表现复杂，且在木薯生长的12个月里，其对叶片、茎和根都会造成损害，因此需要确定对基因型反应进行分类的适当方法以及最佳评估阶段。本研究旨在：1）基于症状表现确定基于地块的CBSD遗传力；2）基于症状表现对CBSD的基因型抗性进行分类。在此，在纳穆隆格对41个基因型进行了为期两年的评估，并在另外三个地点进行了额外评估。评估在种植后3个月、6个月、9个月和12个月进行。基因型对CBSD的反应差异显著。获得了高达0.81（发病率）和0.71（严重程度）的高广义遗传力估计值。对于根和叶的严重程度，平均病害严重程度评分的广义遗传力估计值（分别为0.53和0.65）高于最大病害严重程度评分（分别为0.33和0.61）。这些发现对于选择合适的CBSD评估方法很重要。基因型在症状类型、发生地点和严重程度方面表现出不同的CBSD反应。这表明基因型在抗性机制上存在差异，可用于CBSD抗性育种。
