First Record of the Fungus Rhizoctonia Solani that Causes Root Rot and Damping off on Catharanthus Roseas L. In Provinis Karbala And

Abstract

This study was conducted with the aim of isolating and diagnosing the fungus that causes root rot and seedling death of Catharanthus roseas L. in some nurseries in the governorates of Babylon and Karbala and to test its pathogenicity in the laboratory and under greenhouse conditions. The results showed that 30 isolates of the fungus Rhizoctonia solani were phenotypically diagnosed. Isolate RK22 significantly outperformed the other isolates in reducing the percentage of germination of red radish seeds on Water agar media, as the germination percentage in it was 0.00% and the percentage of inhibition was 100% compared to the comparison treatment in which the percentage of seed germination was 100%. The results of the plastic pots experiment in the greenhouse also showed that the results matched the laboratory experiment, as isolate RK22 was significantly superior in reducing the germination rate, which amounted to 3.33% and an inhibition rate of 96.67% when treating the seeds of Catharanthus roseas plant with the isolated fungi compared to the comparison treatment, in which the percentage of germination reached 100%. The results of the molecular diagnosis showed that the most pathogenic isolate RK22 belongs to the fungus Rhizoctonia solani, and it was deposited in the American Gene Bank underthe entry number.