Especificidade de Trichoderma spp. no parasitismo de fungos fitopatogênicos produtores de escleródios

Abstract

Some soil-dwelling phytopathogenic fungi can survive saprophytically or through resistance structures, such as sclerotia, making it difficult to manage the disease caused by these agents.In this context, biological control has been widely studied and used, with the genus Trichoderma being one of the most widely used agents in the control of soil pathogens.This study aimed to evaluate the genetic diversity and specificity in the parasitism of sclerotia of Rhizoctonia solani, Sclerotinia sclerotiorum and Agroathelia rolfsii by isolates of Trichoderma spp., as well as their potential in promoting plant growth and suppressing R. solani in a common bean bioassay.Isolations were made from plants, leaf litter, and soils from different locations in Minas Gerais. The genetic diversity of 98 isolates was analyzed using the BOX-PCR technique. Representative isolates from the BOX-PCR groups were selected for molecular identification based on amplification of the tef-1α gene.Ten isolates were selected to evaluate their specificity in parasitism of sclerotia of R. solani, S. sclerotiorum and A. rolfsii.These 10 isolates were then tested in a bioassay with common bean plants, in which the following were evaluated: first emergence count, emergence speed index and final emergence, shoot and root length, and the incidence of the disease caused by R. solani.BOX-PCR analysis revealed that the 98 isolates were distributed into 58 groups, with 58.51% consisting of groups with more than one isolate and 41.4% consisting of groups of a single isolate.Of the 20 representative isolates analyzed, six species were identified: T. pseudoasperelloides, T. zelobreve, T. anisohamatum, T. amoenum, T. linzhiense, T. subuliforme and a possible new species.Trichoderma pseudoasperelloides LFM0081 and LFM0027 and T. zelobreve LFM001 stood out for parasitizing and reducing the viability of the sclerotia of S. sclerotiorum and R. solani and A. rolfssi.The isolates T. pseudoasperelloides LFM0081, LFM0085 and T. anisohamatum LFM00102 provided an increase in the emergence percentage and growth of common bean plants, in addition to reducing the incidence of disease and damping-off caused by R. solani, demonstrating potential for biocontrol.The results demonstrate the potential of Trichoderma spp. in biocontrol, although variations among isolates reinforce the importance of complementary studies for validation and selection of promising isolates.