Etiologia e prevalência das manchas de cladódios da palma forrageira miúda nos estados de Alagoas e Pernambuco

Abstract

Nopalea cochenillifera Nopalea cochenillifera Salm-Dyck is a crop of extreme importance in the arid and semi-arid zones of several countries. In Brazil, it is widely used in the states of Alagoas, Pernambuco, Paraíba, Rio Grande do Norte and Ceará, serving as a food source for animals during the dry season. In spite of its rusticity, the palm can be host to a series of pathogens, mainly of fungal nature, which, in addition to rotting, cause cladodes patches that are initially characterized by brown and then necrotic stains, which can later be observed on the other side Of the cladode, causing fall of the infected tissue, that in certain conditions, can compromise the production. However, studies on cladodes of small forage palm are scarce, especially those that are based on the identification of the pathogens and epidemiological aspects of the diseases. In this context, the objective of this study was to determine the etiology and prevalence of phytopathogens involved in cladodeal patches and to identify and characterize species belonging to the Botryosphaeriaceae family associated with patches of forage palm cladodes (N. cochenillifera) in Northeast Brazil. Cladodes presenting symptoms of spots on their surface were collected in eight regions, five of which were in Alagoas and three in Pernambuco. The fungal isolates were obtained from typical lesions of the diseases in small palm cladodes and identified based on molecular, morphological and cultural analyzes. A total of 118 pathogenic isolates were obtained, which were associated to nine fungal genera: Fusarium, Neoscytalidium, Colletotrichum, Macrophomina, Neopestalotiopsis, Altenaria, Lasiodiplodia, Diaporthe and Neofusicoccum, according to ITS region sequence analyzes and morphocultural characteristics. In addition, analyzes of the prevalence of pathogens obtained by collection region were performed. These analyzes showed that the most prevalent genera were Neoscytalidium and Fusarium. In view of the molecular characterization of the Botryosphaeriaceae species based on the partial sequences of Transcribed Internal Space (ITS) and genes, Stretching Factor (EF1-α) and β-tubulin, it was possible to identify two species of Lasiodiplodia, L. theobromae and L Jatrophicola, one of Macrophomina, M. alagoensis sp. nov., One of Neofusicoccum, N. batangarum and one species of Neoscytalidium, Ne. hyalinum, the first four being associated with the brown spot, whereas Ne. hyalinum was associated with spot- squamous. The species L. theobromae and N. batangarum have already been described occurring in small palm, however, the present study constitutes the first records of L. jatrophicola, M. alagoensis and Ne. hyalinum in this culture.