Diversity of <i>Colletotrichum</i> spp. in Legumes and Weeds in Northeast Brazil, With a Description of a New Species in the <i>C. acutatum</i> Complex

ABSTRACT In Brazil, leguminous crops of high commercial and social value are affected by anthracnose caused by Colletotrichum spp. Additionally, Colletotrichum spp. can infect weeds, ensuring their survival even in the absence of the cultivated host. The present study aimed to (i) identify species of Colletotrichum in cultivated legumes and symptomatic weeds using phylogenetic and morphological markers; and (ii) evaluate the pathogenicity and the ability of the obtained isolates to cause disease in six species of legumes. Fungal isolates were obtained in 2017 and 2018. Twenty‐two isolates were collected from rural producers in municipalities of states in the northeast region of Brazil. The isolates were identified by morphological markers and multilocus analysis of gene regions. Pathogenicity tests on the original hosts were conducted with 18 isolates. The host range of 12 isolates was evaluated on plants of Canavalia ensiformis , Crotalaria breviflora , Crotalaria ochroleuca , cowpea, common bean and soybean. Six species of Colletotrichum belonging to the acutatum, boninense, gloeosporioides, orchidearum, magnum and truncatum species complexes were identified. A new species, named Colletotrichum piauiense of the C. acutatum species complex obtained from Crotalaria spectabilis and Spigelia anthelmia plants was characterised. Several pathosystems are described for the first time in Indigofera hirsuta , cowpea and Mucuna pruriens among others. Koch's postulates were completed and the lack of specificity of the isolates between cultivated plants and weeds was confirmed. These results contribute to the knowledge of the diversity of Colletotrichum occurring in Brazil and provide a foundation for developing management strategies.