Characterization of Rhizoctonia spp. in strawberry cultivation areas and investigation of biological control possibilities with Trichoderma spp. against black root rot disease

This study was carried out to investigate the anastomosis groups (AG) of Rhizoctonia spp., an important root rot agent in strawberry, and the possibilities of using Trichoderma spp. for biological control of the disease. In Mersin, Bursa and Konya provinces, which are of great importance in strawberry production, plants showing disease symptoms and soil samples from the rhizosphere were collected from 173 gardens in the 2020 production season. As a result of isolation studies, 122 Rhizoctonia spp. and 180 Trichoderma spp. isolates were obtained. ITS region of Rhizoctonia spp. was amplified and sequenced with ITS1 and ITS4 primers and anastomosis groups were determined by BLAST analysis. Seven different Rhizoctonia AG groups were found; multinucleate Rhizoctonia AG-4 HGI and binucleate Rhizoctonia AG-A, AG-Fa, AG-G, AG-K, AG-V and AG-W. Binucleate AG-V and AG-W are the first records for Turkey and the first in the world in strawberry. Binucleate Rhizoctonia AG-Fa and multinucleate AG-4 HGI are the first records in strawberry in Turkey. Tef1, rpb2 and ITS loci of Trichoderma spp. were amplified and species identification was performed by sequencing analysis. Isolates of Trichoderma spp. were classified into 11 different species as T. atroviride, T. arundinaceum, T. gamsii, T. citrinoviride, T. hamatum, T. afroharzianum, T. harzianum, T. koningii, T. koningiopsis, T. spirale and T. virens. In this study, T. koningii, T. gamsii, T. atroviride, T. koningiopsis, T. arundinaceum, T. hamatum and T. spirale were detected in strawberry production areas for the first time in Turkey. T. arundinaceum is the first record detected in our country. Binucleate Rhizoctonia AG-A isolate SR43, which is the most common and highly virulent isolate, was subjected to dual culture inhibition tests in Petri dishes. Trichoderma spp. isolates were found to have inhibition rates between 39-100%. Pot efficacy tests were carried out with one isolate each of T. gamsii, T. spirale, T. harzianum, T. atroviride and T. koningii which showed the highest effect in the inhibition test. In the control, 85% disease severity occurred. T. harzianum and T. spirale treatments were the most effective isolates against the disease with 82.35% effect. As a result of the study, it is thought that local Trichoderma spp. species can be used for biological control against the black root rot disease caused by binucleate Rhizoctonia AG-A in strawberry.