Selection of melon genotypes with resistance to Didymella bryoniae using a diallel approach

ABSTRACT. The development of melon lines resistant to gummy stem blight (GSB) is an important strategy for decreasing losses caused by this disease. Thus, selecting the best parents for such a goal is essential. We evaluated the general (GCA) and specific (SCA) combining abilities of lines and accessions to guide the selection of the most promising parents to develop GSB-resistant lines. Six genotypes representing two groups (group I - susceptible: group II - resistant) were crossed in a partial diallel mating design. The genotypes were evaluated for disease expression using a rating scale from 0 (resistant) to 4 (susceptible). Estimates of GCA were negative and significant for the accessions PI 420145 and PI 482398, which can be suggested for crosses aimed at obtaining melon lines resistant to GSB. There is a reciprocal effect for the resistance of melon genotypes to Didymella bryoniae, especially when PI 482398, PI 420145, and PI 140471 are crossed with JAB-20. Such results indicate that maternal effects may be involved in the resistance to gummy stem blight.

摘要：培育抗蔓枯病（gummy stem blight, GSB）的甜瓜品系是降低该病害造成损失的重要策略，因此选育适配该育种目标的最优亲本至关重要。本研究对甜瓜品系与种质资源的一般配合力（general combining ability, GCA）和特殊配合力（specific combining ability, SCA）进行评估，以指导筛选最具潜力的亲本，用于培育抗蔓枯病甜瓜品系。本研究采用部分双列杂交设计，对代表两个类群的6份基因型材料开展杂交：类群I为感病材料，类群II为抗病材料。采用0（抗病）至4（感病）的分级标准对材料的病害表现进行评价。结果显示，种质PI 420145与PI 482398的一般配合力估计值为负值且具有统计学显著性，因此可推荐用于旨在培育抗蔓枯病甜瓜品系的杂交组合。甜瓜基因型对瓜类蔓枯病菌（Didymella bryoniae）的抗性存在正反交效应，尤其当PI 482398、PI 420145和PI 140471与JAB-20进行杂交时该效应更为显著。上述结果表明，甜瓜对蔓枯病的抗性可能受母本效应调控。