Survival and infectivity of the reniform nematode, Rotylenchulus reniformis, in relation to moisture stress in soil without host*

The pre-adult females and males of Rotylenchulus reniformis survived under six levels of moisture stress ranging from 0.02 to 21.3 bars in sandy loam soil for 450 days in the absence of host. The population density declined faster during the initial three months period and slowly thereafter. Nine to 33 per cent R. reniformis were found to survive at various moisture tensions after 450 days. Survival was better in relatively dry soil compared to moist and wet soil. Moisture tension of 3.0 bars was found optimum for longer survival. The nematodes in soil with high moisture tension were found to survive in tightly coiled anhydrobiotic state. A few individuals were also loosely coiled in soil with sufficient moisture. The infectivity, rate of development and fecundity of the surviving nematodes was adversely affected with an increase or decrease in moisture tension from 3.0 bars. The nematodes reactivated after 180and 450 days infected and reproduced, at lower rates than the fresh nematodes, on the root of green gram (Vigna radiata).