Caracterização e identificação de espécies de Colletotrichum associadas à antracnose de anonáceas no estado de Alagoas

Abstract

Anthracnose is an important disease of Annonaceae, mainly caused by Colletotrichum gloeosporioides. Recent work in Colombia and Mexico identified C. acutatum infecting the soursop, and C. fragariae and C. orbiculare in cherimoya fruit. The objective of the study was to identify possible associations of species of Colletotrichum infecting the culture of pineapple and guanabana in the state of Alagoas. Single spore colonies of Colletotrichum obtained from leaves displayed typical symptoms of the disease were collected in the municipalities of Maceió, Palmeira dos Índios and União dos Palmares. The isolates were characterized morphologically by conidia and appressoria, staining of the colony, mycelial growth rates in BDA, sequence analysis of the rDNA ITS region and pathogenicity test. Fifty-one isolates, chosen according to the results of morphological, cultural and molecular, were pathogenic when inoculated on detached leaves of sugar apple and soursop. According to the cultural characteristics of the isolates were separated into four distinct groups: A, B, C and D. The G-A was formed by sixteen isolated, G-B twenty-one isolates, G-C and G-D four isolates with ten isolates representing 30%, 43%, 8% and 19% of the isolates, respectively. In morphology, the isolates were grouped into three groups: A, B and C. The G-A was formed by thirty-two isolates, which showed typical features of C. gloeosporioides. The GB with fifteen isolates showed characteristics of C. boninense. And the G-C grouped four isolates with similar characteristics to the species C. fragarie. Based on the sequence of rDNA identity of these isolates showed 99 to 100% with the species C. gloeosporioides, C. boninense, C. fragarie and Glomerella magna. A phylogenetic tree was constructed from sequences of rDNA. The isolates are separated by genetic similarity into three distinct groups (GI, GII and G-III), with the different species of Colletotrichum. The G-I grouped the isolates of C. gloeosporioides and C. fragarie. Twenty-eight isolates showed similarity to C. gloeosporioides and only five isolates with C. fragarie. The G-II grouped fourteen isolates, all genetically related C. boninense, the second most common species. The G-III grouped four isolates, which are phylogenetically related to the species G. magna. The heterogeneity found in the coloration of the colonies of the fifty-one isolates did not allow a reliable identification. However, the morphological characteristics contributed to the identification of most of them, confirming the sequence data of the rDNA region. Thus, according to results obtained in this study, we demonstrate that at least four species of Colletotrichum are responsible for causing anthracnose on sugar apple and soursop in the state of Alagoas: C. gloeosporioides, C. boninense, C. fragariae and G. magna, as first reported occurrence of the last three in these cultures.