Marcenaro Delfia, Valkonen Jari P T
Nicaraguan Institute of Agricultural Technology (CNIAB-INTA), Managua, Nicaragua.
Department of Agricultural Sciences, University of Helsinki, (Latokartanonkaari 7), Helsinki, Finland.
PLoS One. 2016 Dec 20;11(12):e0168662. doi: 10.1371/journal.pone.0168662. eCollection 2016.
Common bean (Phaseolus vulgaris L.) is an important legume with high nutritional value. In Nicaragua, certified healthy seeds of local bean varieties are not available, and seedborne fungi have gained little attention. Here, were surveyed seedborne pathogenic fungi in an important local bean cultivar, 'INTA Rojo'. Beans grown in the four main production areas in Nicaragua (Boaco, Carazo, Estelí, Matagalpa) for future use as seed stock were sampled from four seed storehouses and six seed lots. A total of 133 fungal strains were isolated from surface-sterilized beans and inoculated to healthy lima beans (Phaseolus lunatus) under controlled conditions. Eighty-seven isolates caused symptoms of varying severity in the seedlings, including discoloration, necrotic lesions, cankers, rot, and lethal necrosis. Pathogenic isolates were divided into eight phenotypically distinguishable groups based on morphology and growth characteristics on artificial growth medium, and further identified by analysis of the internal transcribed spacer sequences (ITS1 and ITS2) of the ribosomal RNA genes. The pathogenic isolates belonged to eight genera. Fusarium spp. (F. chlamydosporum, F. equiseti, F. incarnatum), Lasiodiplodia theobromae, Macrophomina phaseolina, and Penicillium citrinum were the most damaging and common fungi found in the seed lots. Furthermore, Corynespora cassiicola, Colletotrichum capsisi, Colletotrichum gloeosporioides, Aspergillus flavus, and Diaporthe sp. (Phomopsis) were seedborne in cultivar 'INTA Rojo' and found to be pathogenic to bean seedlings. This study reveals, for the first time, many seedborne pathogenic fungi in beans in Nicaragua; furthermore, prior to this study, little information was available concerning F. equiseti, F. incarnatum, L. theobromae, C. cassiicola, and Diaporthe spp. as seedborne pathogens of common bean. Our results lay the basis for developing diagnostic tools for seed health inspection and for further study of the epidemiology, ecology, and control of the pathogenic fungi of common beans in the field.
菜豆（Phaseolus vulgaris L.）是一种具有高营养价值的重要豆类。在尼加拉瓜，当地豆类品种的经过认证的健康种子无法获得，且种传真菌很少受到关注。在此，我们对当地一个重要的菜豆品种‘INTA Rojo’中的种传致病真菌进行了调查。从四个种子仓库和六个种子批次中采集了在尼加拉瓜四个主要产区（博阿科、卡拉佐、埃斯特利、马塔加尔帕）种植的、未来用作种子储备的菜豆。从表面消毒的菜豆中总共分离出133株真菌菌株，并在可控条件下接种到健康的利马豆（Phaseolus lunatus）上。87个分离株在幼苗中引起了不同严重程度的症状，包括变色、坏死斑、溃疡、腐烂和致死性坏死。根据在人工生长培养基上的形态和生长特征，致病分离株被分为八个表型可区分的组，并通过分析核糖体RNA基因的内部转录间隔区序列（ITS1和ITS2）进一步鉴定。致病分离株属于八个属。镰孢菌属（Fusarium spp.）（F. chlamydosporum、F. equiseti、F. incarnatum）、可可毛色二孢（Lasiodiplodia theobromae）、菜豆壳球孢（Macrophomina phaseolina）和桔青霉（Penicillium citrinum）是在种子批次中发现的最具危害性且常见的真菌。此外，卡西棒孢（Corynespora cassiicola）、辣椒炭疽菌（Colletotrichum capsisi）、胶孢炭疽菌（Colletotrichum gloeosporioides）、黄曲霉（Aspergillus flavus）和Diaporthe sp.（拟茎点霉属）在‘INTA Rojo’品种中是种传的，并且被发现对菜豆幼苗具有致病性。这项研究首次揭示了尼加拉瓜菜豆中的许多种传致病真菌；此外，在本研究之前，关于F. equiseti、F. incarnatum、可可毛色二孢、卡西棒孢和Diaporthe spp.作为菜豆种传病原体的信息很少。我们的结果为开发种子健康检测诊断工具以及进一步研究菜豆致病真菌在田间的流行病学、生态学和防治奠定了基础。
