Abstract:

To determine the relationship between population density of Meloidogyne graminicola and yield loss in upland rice, the effects of Meloidogyne graminicola initial population density (Pi) on the yield of upland rice and reproduction of nematodes were evaluated in pot experiments under the screen house condition with dry planting and management. The results revealed a linear regression relationship where rice parameters such as root length, root weight, plant height, tiller number, panicle length, 1000-seed weight and single basin grain weight decreased as Pi increased. The yield loss ranged from 28.4% at a Pi of 2 eggs and J2/100 cm³ soil to 67.8% at a Pi of 200 eggs and J2/100 cm³ soil. The reproduction factor of nematodes followed a declining trend with Pi. The relationship between population density and relative yield followed the Seinhorst model, Y=0.24+0.76(0.3252)^(Pi). A significant positive correlation was noted between upland rice yield loss and Pi of 2 to 200 eggs and J2/100 cm³ soil under dry planting and management, indicating a high risk of harm to upland rice caused by M. graminicola.

Key words: Meloidogyne graminicola, initial population density, upland rice, yield loss, reproduction factor, pot experiment, seinhorst model, resistance assessment, planting method, population number determination, disease occurrence, damage assessment, inoculum collection method, plant growth dynamics