Studies of Effect of Trace Aliments on Pathogenicity of Rhizcotonia Solani & Susceptibility of Rice plant

Abstract

Cultural variability amon_g 25 isolates of Rhizoctonia so/ani causing sheath blight in rice (from different parts of India) was observed. growth pattern and colony growth showed great diversity in all the isolates. Based on colony pigmentation, all the isolates were assigned into six groups i.e.whitish brown, light brown, yellowish brown, Dark brown, pale brown and milkish brown. Isolates were classified into three groups on the basis of growth rate i.e. fast, medium and slow growing. Out of 25 isolates, seven isolates had sclerotia! diameter between the range of 1.21 to 1.75mm. and seventeen isolates had sclerotia! diameter between the range of 1.75 to 2.94mm. The isolate,RS-24 didn't produced any sclerotia. Among 25 RAPD primers used, only 18 primers resulted in the PCR products and rest of the 7 primers couldn't resulted in any PCR product. Out of 18 primers resulting in PCR products, 17 RAPD primers gave polymorphic bands whereas one primer i.e. UBC-373 resulted in one monomorphic band also. The cluster dendogram revealed that all the 25 isolates of R. so/ani can be grouped into two major clusters at a cut off similarity coefficient level 0.53. Among these two clusters, the cluster 1st was having only one isolates i.e. RS-16, whereas the cluster lind was largest with 24 isolates. The highest level of similarity coefficient i.e. 0.94 was observed between the isolates RS-11 and RS-12 both belonging to Uttar Pradesh followed by 0.92 between RS-20 and RS-21also belonging to Uttar Pradesh. Lowest level of similarity coefficient i.e.0.51 was observed between isolates RS-1 belonging to Punjab and RS-16 belonging to Uttar Pradesh. Supply of sucrose helped the R. so/ani in minimizing the incubation period and also to increase the size of sheath blight lesions. Supply of sucrose + fructose + lactose together helped the R. so/ani in increasing the number of lesions produced on the host. Additional supply of alanine, calcium nitrate and sodium nitrate helped R. so/ani to increase its virulence and aggressiveness on rice plants. Supply of three vitamins together i.e. biotin +calcium pentothenate +thiamin as nutrition supplement helped the R. so/ani to reduce the incubation period, whereas supply of inositol or biotin, helped the pathogen to increase the lesion length whereas thiamin alone was able to increase the disease severity as a whole. Application of Iron, Zinc and Manganese was able in reducing level of sheath blight disease and also increase the phenol quantity in rice plants. Sulphur and Molybdenum also helped rice plants in reducing the level of sheath blight in rice crop.