REACTIONS OF LIMA BEAN (Phaseolus lunatus L.) ACCESSIONS TO Colletotrichum truncatum

ABSTRACT Lima bean (Phaseolus lunatus) can be considered as an alternative income and food supply to farmers of the Brazilian Northeast. This crop has faced serious sanitary problems. Among the most important diseases that attack this crop, the anthracnose caused by Colletotrichum truncatum requires greater attention. This study aimed to determine the resistance of lima bean accessions to the isolates of C. truncatum. Detached leaves were used from ten lima bean accessions, originated from production fields in Paraíba State - Brazil. They were artificially inoculated with ten isolates of C. truncatum. The isolates were grown on bean-dextroseagar medium under temperature 27 ± 2 °C and a photoperiod of 12 hours, for fourteen days. The evaluations of the accessions’ resistance to the isolates were performed at 5, 7, 9, 11 and 13 days after inoculation (DAI), adopting a scale of notes, and the results were transformed in the area under the disease progress curve. The research was carried out in completely randomized design, in a 10x10 factorial arrangement (accessions x isolates) with 12 replications. The first symptoms of anthracnose on the detached leaves appeared from the third day after inoculation. The accessions were grouped from highly to moderately resistant or susceptive. The aggressiveness among C. truncatum isolates varied depending on the genetic variability of the lima bean accessions used. Accessions with significant resistance levels to anthracnose can be used as resistance sources in future breeding programs.

摘要 利马豆（Phaseolus lunatus）可作为巴西东北部农民的替代收入来源与粮食补给。该作物曾面临严重的植保问题，其中由菜豆炭疽菌（Colletotrichum truncatum）引发的炭疽病是危害该作物的最重要病害之一，需予以重点关注。本研究旨在测定利马豆种质对菜豆炭疽菌菌株的抗性。试验采用源自巴西帕拉伊巴州生产田的10份利马豆种质的离体叶片，人工接种10株菜豆炭疽菌菌株。菌株于豆粉葡萄糖琼脂培养基上，在27±2℃、12小时光周期条件下培养14天。分别于接种后5、7、9、11、13天（Day After Inoculation，DAI）采用评分法对参试种质的菌株抗性进行评价，并将结果转换为病害进展曲线下面积。试验采用完全随机设计，设置10×10析因排列（种质×菌株），共12次重复。离体叶片上的炭疽病初始症状于接种后第3天出现。参试种质可分为高抗、中抗及感病三类。菜豆炭疽菌菌株的致病力因所用利马豆种质的遗传变异而存在差异。对炭疽病具有显著抗性的种质可作为后续育种项目的抗源材料。