Studies on the pathogenicity of three host races of Rotylenchulus reniformis on castor

Three races (race 2, 3 and 4) of Rotylenchulus reniformis were identified using host differential from 20 populations collected from Aligarh, India. Pathogenicity tests were conducted using 250, 500, 1000, 2000, 4000 and 8000 immature females/kg soil of three races of R. reniformis on castor. The threshold inoculum levels of Race-2, Race-3 and Race-4 on castor were 500, 1000 and 2000 immature females/kg soil, respectively. Out of these three races present in Aligarh district, Race-2 was found more pathogenic followed by Race-3 and Race-4. Infected plants with all the three races of reniform nematode showed stunting, necrosis, leaf shedding and growth reduction at and above the inoculum threshold level of each race. Reduction in castor growth was directly proportional to the inoculum level of R.reniformis. The rate of nematode multiplication was density dependent.