Infectivity, Development, and Reproduction of Heterodera cajani on Pigeonpea: Influence of Soil Moisture and Temperature.

The effect of soil moisture on penetration, development, and reproduction of Heterodera cajani on pigeonpea (cv. ICPL 87) was investigated in growth chambers held at 20 and 25 C, and in a greenhouse where temperature fluctuated between 25 and 32 C. Averaged across temperatures, the percentage of juveniles that penetrated roots was 34.3, 31.8, 8.8, and 3.7% at 24, 32, 16, and 40% soil moisture levels, respectively. Numbers of females per root system 4 weeks after infesting soil with second-stage juveniles was 79.6 at 24%, 65.3 at 32%, 26.1 at 16%, and 2.9 at 40% soil moisture. Nematode reproduction was greatest (P = 0.001) at 24% soil moisture and 25 C. Reproductive factor was 19.4 at 24%, 15.2 at 32%, 5.7 at 16%, and 0.5 at 40% soil moisture level. Nematode penetration, development, and reproduction at different moisture levels were greater (P = 0.01) at 25 and 25-32 C than at 20 C. Plant growth was retarded at 40% soil moisture and 20 C in comparison to that at 24 and 32% moisture levels and 25 C. This information on influence of temperature and soil moisture will be helpful in developing models for predicting changes in H. cajani densities in pigeonpea fields during rainy and postrainy dry seasons in the semi-arid tropics.