PLANT-DAMAGE AND YIELD LOSS CAUSED BY THE RICE ROOT-KNOT NEMATODE, MELOIDOGYNE-GRAMINICOLA IN DEEP-WATER RICE

Studies on the magnitude of plant damage and yield loss in deepwater rice caused by the rice root-knot nematode, Meloidogyne graminicola, showed that the infested plants were stunted and were not able to elongate enough to cope with the increase of flood water and thus were drowned. It was found that about 50% of infested tillers were drowned under flooding, both in the field and under artificially inoculated conditions. A yield loss of 9.1-22.2% was recorded in diseased patches under field conditions. Yield components such as number of filled and percentage of unfilled grains per panicle and 1000 grain weight were found to be affected by this nematode, both under naturally infested and artificially inoculated conditions. One thousand or more juveniles per seedling were found to be most damaging, both in terms of plant damage and yield loss in a pot test.