Resistance of the wild tomato Solanum habrochaites to Phytophthora infestans is governed by a major gene and polygenes

Abstract: This work aimed to study the inheritance of resistance to Phytophthora infestans in tomato plants, using the maximum likelihood estimation function. The susceptible cultivar Santa Clara (Solanum lycopersicum) was used as the female genitor and the P. infestans resistant S. habrochaites f. glabratum accession (BGH 6902) as the male genitor. F1 plants from the crossing were self-pollinated to produce F2 progenies, and also backcrossed with PR and PS to produce BC1:R and BC1:S generations, respectively. The tomato plants were inoculated 50 days after transplanting. Disease severity was evaluated via a diagrammatic scale. Comparison of the genetic models created using the maximum likelihood function revealed that the inheritance of resistance to P. infestans in S. habrochaites is conferred by a major gene with additive and dominance effects, polygenes with additive effects, plus the environmental effect. Vertical resistance can be explored using genes with major effects. Programs of recurrent and maker-assisted selection are considered efficient strategies with which to select genotypes that hold P. infestans resistance conferred by polygenes.

摘要：本研究借助最大似然估计函数，探究番茄植株对致病疫霉（Phytophthora infestans）的抗性遗传规律。试验以感病品种圣克拉拉（普通番茄，Solanum lycopersicum）作为母本，以抗致病疫霉的哈氏番茄光滑变型（S. habrochaites f. glabratum）材料BGH 6902作为父本。将杂交获得的F₁植株自交以获得F₂后代群体，同时分别与抗性亲本（PR）和感病亲本（PS）回交，分别得到BC₁:R与BC₁:S世代群体。于移栽后50天对番茄植株接种致病疫霉，采用图解分级法评估病害严重程度。通过最大似然函数构建的遗传模型比较分析显示，哈氏番茄光滑变型对致病疫霉的抗性遗传由兼具加性与显性效应的主效基因、仅具加性效应的微效多基因，以及环境效应共同决定。垂直抗性可借助携带主效效应的基因开展研究与应用。轮回选择及标记辅助选择（maker-assisted selection）育种方案被视为筛选携带多基因调控的致病疫霉抗性基因型的高效策略。