Cacao families and parents selected as resistant to natural infection of Moniliophthora perniciosa

Abstract The known sources of resistance to witches' broom (WB), a severe disease of cacao, are limited. Aiming to identify families and parents resistant to Moniliophthora perniciosa, a population of 22 families was evaluated by assessing the number of brooms formed per tree during 10 years under field conditions. The population was established in randomized blocks with three replications of 12 plants each. Significant differences were observed among families. The most outstanding families were NA33 x RB39 and RB39 x P4B, which presented the lowest WB incidence during 10 years. The increase in natural field infection of Scavina clones families and their descendants were clearly demonstrated after 2006. The existence of additive effects for resistance appears clearly for families, which had other source of resistance associated with Scavina. Clones RB39, RB36, P4B, NA33 and CSUL3 are promising parents for pyramiding resistance genes and increasing the stability and durability of resistance to WB.

摘要 可可严重病害丛枝病（Witches' Broom, WB）的已知抗源极为有限。为筛选抗嗜丝单胞霉（Moniliophthora perniciosa）的家系与亲本，本研究对22个家系组成的试验群体开展了为期10年的田间抗性评价，通过统计单株形成的丛枝数量完成抗性鉴定。该试验采用随机区组设计，设置3次生物学重复，每个小区定植12株供试植株。结果显示，不同家系间的抗病性存在极显著差异。其中，NA33×RB39与RB39×P4B两个家系在10年的鉴定周期内WB发病率最低，抗病表现最为优异。2006年后，斯嘉维纳（Scavina）无性系家系及其后代的田间自然发病程度显著升高。进一步分析表明，携带与斯嘉维纳相关抗源的家系，其抗病性存在显著的加性遗传效应。无性系RB39、RB36、P4B、NA33与CSUL3可作为优良亲本，用于聚合抗WB基因，进而提升可可丛枝病抗性的稳定性与持久性。