The effect of root-knot nematode, Meloidogyne graminicola, on the quality and vigour of rice seed

The root-knot nematode, Meloidogyne graminicola, is a serious pest of rice known to reduce grain yield. The effects of a series of infestation levels of M. graminicola on the nutritional and seed quality parameters of the grain have been studied under pot and field conditions using two cultivars of rice, a basmati, cv. Pusa Sugandh-5 and a non-basmati, cv. Pusa-44. The 1000 grain weight was significantly reduced by as much as 44.5% in cv. Pusa Sugandh-5 and 50.7% in cv. Pusa-44 seed when the parent plants were grown in soil with very high levels of M. graminicola infestation. The protein and amylose contents of the grains were significantly reduced in both the rice cultivars. The seed germination percentages of both the rice cultivars were also reduced as the nematode inoculation rates increased from 1-8 second-stage juveniles (J2) cm(-3) in a pot experiment. Similar trends were also observed in field conditions. There was a significant decrease in the seedling vigour indices of both the rice cultivars. These results showed that the rice grains produced on plants infected with the nematode M. graminicola were lighter in weight and had poorer nutrient qualities, such as amylose and protein content. Further, if these grains were used as seed, the germination percentage was lower and, even more importantly, seed vigour was poor compared to the seed obtained from plants grown in M. graminicola-free soil.