Reaction of lima bean genotypes to Macrophomina phaseolina

ABSTRACT Charcoal rot, caused by Macrophomina phaseolina, is an important disease of lima bean (Phaseolus lunatus L.) in the Northeast of Brazil. Considering that there are no reports of resistance to this disease in Brazil, 37 lima bean accessions were evaluated for their resistance reaction and resistance stability against isolates of M. phaseolina in two periods of the year (February-March and July-August 2016), with the aim of selecting genotypes with the potential for use in the management of this disease. Seeds were inoculated at sowing, using rice grains with husk that were colonized by the pathogen. The evaluations of genotypes were carried out at every five days, from the tenth day after sowing, using a score scale and dividing them into six reaction classes. From a population of 37 accessions of P. lunatus, no immunity reaction to M. phaseolina was seen; however, thirteen accessions presented the lowest severity levels and greatest stability in the two seasons: UFPI 892, UFPI 908 and UFPI 905, which were considered resistant to the isolate COUFPI 06. The resistance reaction of accessions considered resistant varied depending on the isolate of M. phaseolina. Accession UFPI 908 expressed the most promising results for resistance and stability of resistance against the isolates COUFPI 06, COUFPI 08 and COUFPI 10. Therefore, accession UFPI 908 constitutes a promising source of resistance to M. phaseolina, making possible its use in breeding programs and in integrated management of charcoal rot.

摘要：由菜豆壳球孢菌（Macrophomina phaseolina）引发的炭腐病（Charcoal rot），是巴西东北部地区利马豆（Phaseolus lunatus L.）的重要病害。鉴于巴西境内尚未有该病害抗性种质的相关报道，本研究于2016年的两个时段（2-3月与7-8月），对37份利马豆种质材料开展抗菜豆壳球孢菌分离物的抗性反应及抗性稳定性评价，以期筛选可用于该病害防控的潜力基因型。试验采用被病原菌定殖的带壳稻粒作为接种体，于播种时完成种子接种。自播种后第10天起，每5天开展1次种质抗性评价，通过评分分级法将材料划分为6个反应等级。对37份利马豆种质材料的评价结果显示，未发现对菜豆壳球孢菌具有免疫反应的材料；但其中13份种质在两个试验时段均表现出最低的病害严重度与最优的抗性稳定性，包括UFPI 892、UFPI 908与UFPI 905，这3份种质对分离物COUFPI 06表现为抗性。进一步分析表明，上述被认定为抗性的种质，其抗性反应会因菜豆壳球孢菌分离物的不同而存在差异。其中，种质UFPI 908在应对COUFPI 06、COUFPI 08与COUFPI 10这3个分离物时，均展现出最为优异的抗性与抗性稳定性。综上，种质UFPI 908是抗菜豆壳球孢菌的优异抗性资源，可应用于炭腐病的抗病育种项目以及该病害的综合防控体系中。