Análise de espécies de Curvularia associadas à cultura do inhame no estado de Alagoas

Abstract

The yam (Dioscorea cayennensis Lam.) is an important staple crop in the Northeast region of Brazil, mainly in the states of Alagoas, Pernambuco, and Paraíba, the highest producing areas in the region. The crop is affected by pathogens that reduce yield and leaf blight, caused by the fungus Curvularia eragrostidis, can cause considerable crop losses. In the socio-economic context in which this crop is placed, the use of resistant varieties is the most effective control strategy. However, for this strategy to be successful, knowledge of the genetic variability of the pathogen is required. Samples of infected yam leaves were collected in 2005 and 2008, from fields in Chã Preta, Paulo Jacinto, and Viçosa and 73 isolates were obtained. Based on morphological characteristics all isolates were identified as C. eragrostidis. All isolates were pathogenic to yam and there were differences in the values of area under the disease progress curve (P= 0.02). When different isolates were paired in culture, mycelia compatibility in the majority of pairings. Similarity and phylogenetic analyses supported the identification of the species associated to yam leaf blight. The AFLP markers were used to investigate the genetic structure of the population of C. eragrostidis. Gene diversity was high (Ht = 0.31) and there was low differentiation between populations (Gst = 0.06). The population was not structured according to geographical origin. The genetic variability within populations of C. eragrostidis was high.