Multiple resistance to bacterial halo blight and bacterial leaf spot in Coffea spp.*

ABSTRACT Breeding for genetic resistance is an important method of crop disease management, due to the numerous benefits and low cost of establishment. In this study, progenies of 11 Coffea species and 16 wild C. arabica accessions were tested for their response to Pseudomonas syringae pv. garcae, the causal agent of bacterial halo blight, a widespread disease in the main coffee-producing regions of Brazil and considered a limiting factor for cultivation in pathogen-favorable areas; and also to P. syringae pv. tabaci, causal agent of bacterial leaf spot, a highly aggressive disease recently detected in Brazil. Separate experiments for each disease were carried out in a greenhouse, with artificial pathogen inoculations and ideal moisture conditions for disease development. The results showed that C. canephora, C. congensis, C. eugenioides, C. stenophylla, and C. salvatrix progenies, the wild C. arabica accessions Dilla & Alghe and Palido Viridis, and cultivar IPR 102 contain satisfactory levels of simultaneous resistance against bacterial halo blight and bacterial leaf spot. These results are useful in breeding programs for durable resistance to multiple biotic agents, providing new combinations of resistance alleles by hybridization, as well as for phytopathological studies, to identify infraspecific variability of the pathogens.

摘要
遗传抗性育种因其诸多优势且构建成本低廉，是作物病害防控的重要手段。本研究对11个咖啡属（Coffea）物种的后代群体以及16份野生阿拉伯咖啡（Coffea arabica）种质进行了抗性鉴定，以评估其对两种病原菌的抗性：其一为丁香假单胞菌瓜生致病变种（Pseudomonas syringae pv. garcae），该菌是细菌性晕枯病的病原菌，此种病害在巴西主要咖啡产区分布广泛，且被视为病害适宜种植区限制咖啡栽培的关键因素；其二为丁香假单胞菌烟草致病变种（Pseudomonas syringae pv. tabaci），该菌是近期在巴西检出的高致病性细菌性叶斑病的病原菌。
本研究针对两种病害分别开展温室盆栽试验，采用人工接种病原菌并维持病害发生所需的理想湿度条件。试验结果显示，刚果咖啡（Coffea canephora）、Congensis咖啡（Coffea congensis）、尤金尼奥咖啡（Coffea eugenioides）、狭叶咖啡（Coffea stenophylla）、Salvatrix咖啡（Coffea salvatrix）的后代群体，野生阿拉伯咖啡种质Dilla & Alghe与Palido Viridis，以及栽培品种IPR 102，均对细菌性晕枯病和细菌性叶斑病兼具令人满意的兼抗水平。
上述结果可为培育针对多种生物胁迫的持久抗性品种提供支撑，通过杂交聚合抗性等位基因以创制新的抗性组合，同时也可为植物病理学研究提供参考，用于解析病原菌的种内变异特征。