Screening coffee genotypes for brown eye spot resistance in Brazil

Several researchers have attempted to develop coffee plants that are resistant to brown eye spot (BES); however, no coffee cultivars are resistant to the disease. In the present study, a blend of strains from Cercospora coffeicola was inoculated into 19 Brazilian commercial cultivars and 41 accessions from the Germplasm Collection of Minas Gerais to evaluate the genetic resistance ability within the population and select superior genotypes for the breeding program. After predicting the genotypic values of the studied material, the evaluations number necessary for selecting genotypes with accuracy and efficiency was determined based on the data of severity to BES. The action of defense mechanisms plant was also investigated by assessing the levels of total soluble phenolic compounds and soluble lignin in contrasting genotypes for disease susceptibility. Based on the results, the accession MG 1207 Sumatra, had an intrinsic genetic capacity to maintain low levels of severity to BES. The genotype MG 1207 Sumatra can substantially contribute to the development of new cultivars, which may lead to the reduced use of pesticides. According to the accuracy and efficiency results obtained, four evaluations BES severity are sufficient to achieve accuracy, providing expressive genetic gains. Finally, the levels of lignin and phenolic compounds were not found to be associated with the resistance of coffee genotypes to BES.

已有多位研究者尝试培育抗咖啡褐斑病（brown eye spot, BES）的咖啡植株，但目前尚未有对该病害具有抗性的咖啡栽培品种问世。本研究将咖啡尾孢菌（Cercospora coffeicola）的混合菌株接种至19个巴西商业栽培品种以及米纳斯吉拉斯州种质资源库的41份种质材料中，以评估该群体内的遗传抗性能力，并为育种项目筛选优良基因型。在预测供试材料的基因型值后，本研究基于咖啡褐斑病病情分级数据，确定了精准高效筛选基因型所需的评价次数。本研究还通过分析病情抗性存在显著差异的基因型的总可溶性酚类物质与可溶性木质素含量，探究了植株的防御机制作用模式。研究结果显示，种质材料MG 1207 Sumatra具有维持低褐斑病病情等级的内在遗传特性。该基因型MG 1207 Sumatra可显著助力新型咖啡栽培品种的培育，进而减少农药的使用量。基于所获精度与效率结果，仅需4次咖啡褐斑病病情分级评价即可达到理想精度，同时可获得可观的遗传增益。最终研究发现，木质素与酚类物质的含量与咖啡基因型对褐斑病的抗性并无显著关联。