DOI: doask213jdas0
Abstract
Macrophomina phaseolina and Fusarium spp. are soil borne plant pathogens causing seed-, root-, collar- and stem rot, as well as vascular wilt and discoloration. Several isolates obtained during 2014-2015 from rotten stems and roots of sunflower plants, hybrid LG 56.63 CL, from the region of Northeast Bulgaria, were studied for their basic morphological and cultural characteristics, pathogenicity and sensitivity to fungicides. One of the isolates was identified as Macrophomina phaseolina (Tassi) Goidanich and two of them were identified as Fusarium spp. using colony morphology, density and extent of mycelia growth. On PDA, the colonies of Macrophomina phaseolina showed dense growth, initially olive gray, then becoming black. None of the cultures produced pycnidia. Microsclerotia were produced after the 5th day. On PDA the cultures from single-spore isolates of Fusarium spp. formed pink to raspberry and purple colored floccuse mycelium, macroconidia, microconidia and chlamydospores. Pathogenicity tests were carried out in a greenhouse by the stem-tape inoculation method. In vitro sensitivity of Macrophomina phaseolina and Fusarium spp. to five fungicides was determined through the inhibition zone technique (Thornberry’s method). The antagonistic activity of Trichoder-ma viride (Tr 6) against Macrophomina phaseolina and Fusarium spp. in vitro was evaluated by means of the opposite culture method.