MORPHOLOGICAL AND PHYLOGENETIC DIVERSITY OF Rhizoctonia solani Kühn (CANTHARELLALES: CERATOBASIDIACEAE) ISOLATES AFFECTING DIFFERENT HOSTS PLANTS IN MOROCCO

Root and stem rot are serious fungal diseases caused by Rhizoctonia solani Kühn (Cantharellales: Ceratobasidiaceae) on several plant species worldwide.

This study was conducted, during the period between 2015 and 2018, to investigate morphological and phylogenetic diversity of R. solani strains isolated from different crops including melon, watermelon, olive tree, strawberries, tomato, and potato grown in different locations of Morocco. Fungal colonies of all the isolates collected from various host plants were morphologically diverse in color, growth rate and distribution of sclerotia (black scurf of potato).The variability in the growth rates of R. solani isolates was observed after 48 hrs incubation. The mycelium growth rate recorded for RS6 and RS1 isolates ranged between 8.3 and 12.7 mm/day respectively. After 15 days of incubation on PDA medium, the color of the sclerotia was classified into three groups based on the dominant spectral color. Also, distribution of the sclerotia in the colony was observed in the center or periphery of Petri dishes in most isolates except for isolates FOR and R2, which did not produce sclerotia. Molecular characterization, of studied isolates, based on sequence information of the internal transcribed spacer (ITS1–ITS2) and nuclear small subunit rDNA (SSU rDNA) showed that there was no correlation between isolates and their geographical locations and host plant, suggesting a genetic similarity between RS13, RS8, RS6, RS3, RS1 and R1 isolates originating from different locations and host plants. In contrast, this phylogenetic characterization revealed that there is no similarity among R1, FOR and R2 isolates collected from strawberries plants and the same location (Moulay Bousselham). These results may help in the molecular characterization of the pathogen R. solani and for development of disease management strategies.