Pathogenic effect of Meloidogyne graminicola on growth of rice seedlings and susceptibility of cultivars

Pathogenicity test conducted on rice cv. Malvia 36 showed conclusive evidence of the damaging potential of M. graminicola on rice seedlings in terms of plant growth characters. Eventhough maximum reduction in all the plant growth parameters was recorded at 5000 J₂, the significant reduction in shoot & root length and fresh shoot & root weight was observed at 1000 J₂ / kg of soil and was considered as damaging threshold level of M. graminicola. The nematode significantly reduced the growth of rice seedlings: shoot length by 31.2, 44.0 and 63.5%; root length by 39.2, 40.8 and 43.4%; fresh weight of shoot by 42.0, 53.6 and 69.5%; fresh weight of root by 40.2, 42.7 and 49.1%, respectively at 1000, 2000 and 5000 J₂ / kg of soil. The root galls also increased significantly with the increasing levels of nematode inocula with maximum at 2J₂/g being at 2000 J₂ / kg of soil. Wilting of rice seedlings was also observed at 5000 J₂ / kg of soil. Twenty one varieties/ genotypes of rice were screened against M. graminicola and almost all the genotypes showed susceptibility. However, number of root galls varied with genotypes. Maximum numbers of root galls (41.8) were recorded in rice cv. Ratna whereas minimum root galls (2.0) were registered in rice cv. BL-111-3. In general, all the varieties showed yellowing and stunting; however, some varieties viz., BL- 149, PBS- 23, HUR- 3021, and LM- 1 recorded wilting of seedlings.