A soil bioassay, using rice as an indicator plant, and a host susceptibility experiment were conducted to investigate the impact of wheat on population densities of Meloidogyne graminicola in a rice-wheat rotation area of Bangladesh. The bioassay revealed widespread infestations of M. graminicola following wheat harvest. Root-galling severity ratings on a 1 to 9 scale for all 18 fields tested ranged from 1.5 to 7.0 with a mean of 4.8. Root-galling severity in rice nursery seedbeds ranged from 1.0 to 4.4 with a mean of 3.3. In the host susceptibility experiment, all wheat varieties commonly cultivated in ricewheat rotation areas of Bangladesh were determined to be excellent hosts to M. graminicola. The reproduction on wheat roots was 26.4 to 57.9 times the initial nematode population density. The results of these two experiments indicate that wheat is contributing to high population densities of M. graminicola in soil which can negatively impact rice, and possibly wheat, productivity in a rice-wheat rotation.
