Soils of Tropical Dry Forest and with Different Crops Presenting Ascospores of Monosporascus cannonballus

Abstract

The vine decline caused by Monosporascus cannonballus is a limiting factor in different crops in several countries. The objective of this study was to quantify the M. cannonballus ascospores in soils covered with tropical dry forest and areas cultivated with pineapple, cotton, coconut, corn, mango, melon, papaya, sorghum and watermelon. Five areas were sampled in tropical dry forest and every crop. The M. cannonballus ascospores were extracted using the flotation method of sucrose. Ascospores of M. cannonballus were detected in all soil samples from Rio Grande do Norte and Ceará states, including tropical dry forest. There were significant differences among the ascospores densities of M. cannonballus, which varied from 0.55 to 2.21 ascospores g-1 soil. The lower densities were found in areas with cotton, coconut, mango, pineapple, and melon within the first and fifth years of cultivation, in addition to uncultivated areas of tropical dry forest. The highest ascospores density was found in papaya areas. Up to date, there is no study to prove that this crop is considered host of this phytopathogen. Cultivated areas with cucurbitaceous with more years of cultivation presented higher densities of M. cannonballus ascospores in soils from Brazilian semiarid. However, there is no direct relationship between M. cannonballus population density in the soil and the susceptibility of the host being cultivated in the soil at the time of sampling.