Abstract

                                A pot culture experiment was conducted in a glass house to assess the pathogenicity of root-knot nematode, Meloidogyne incognita on Pongamia pinnata. Poly bags (15 cm x 10 cm) were filled up with steam sterilized fine river sand mixed with red earth at the ratio of 3:1. The freshly collected, surface sterilized seeds were sown. Fifteen days after germination of seedlings, second stage larvae of M. incognita were inoculated in the root zone of P. pinnata at the rate of 0,10, 100, 1000 and 10,000 larvae pot-1. Each treatment was replicated four times and arranged in a RBD in glass house at a room temperature of 27°C.The growth parameters such as root length, root weight, shoot length, shoot weight, number of galls, rhizobial nodules, number of egg masses on root, number of larvae, adult females and final soil populations were recorded at 120 DAI. The chlorophyll content and physiological parameters were also recorded at 120 DAI. The results revealed progressive reduction in length and weight of shoot and root significantly with the increase in the level of initial inoculum. The percentage of reduction in shoot length, shoot weight, root length and root weight were 38.6, 41.4, 18.3 and 34.7 per cent, respectively to the initial inoculum of 10,000 larvae when compared to uninoculated control. The percentage of reduction in plant weight was noticed due to the inoculum of M. incognita over uninoculated control. It was found that at an initial inoculum level of 10,000 larvae kg-1 soil, the collar diameter got decreased by 26.3 per cent over control. Significant reduction of rhizobial nodule was recorded for every level of larvae inoculated on P. pinnata. The respective per cent reduction in nodule and its diameter registered was 45.9 and 22.2, 56.4 and 26.7 and 59.2 and 40.0 to 100, 1000 and 10,000 larvae kg-1 soil over uninoculated control. It was found that there was significant reduction in chlorophyll 'a' chlorophyll 'b' and total chlorophyll in the inoculated pots. The data recorded on stomatal conductance, transpiration rate and net photosynthetic rate to the three levels of larvae inoculated showed significant decrease as compared to the uninoculated control.

Key words : Pungam, root - knot nematode, pathogenicity