THE EFFECT OF TEMPERATURE ON RESISTANCE IN AFRICAN RICE (ORYZA GLABERRIMA STEUD.) GENOTYPES TO THE RICE ROOT-KNOT NEMATODE MELOIDOGYNE GRAMINICOLA

Abstract

The rice root-knot nematode, Meloidogyne graminicola, has emerged as a serious soilborne pathogen of rice in most Asian countries. The host response of the M. graminicola-resistant African (Oryza glaberrima) rice genotypes TOG5674, TOG5675, and CG14 was examined at two day/night temperature regimes, 29/26°C and 34/31°C. At the 34/31°C regime, second-stage juvenile population densities in roots of the African rice genotypes increased significantly compared to those of plants grown at the 29/26°C regime, suggesting that the resistance to M. graminicola became ineffective at the latter temperature regime. An increase in temperature also resulted in a significant reduction in all yield-contributing traits and yield of the three African rice genotypes. High variability was recorded in terms of percentage reduction of all traits measured among the genotypes examined at the 34/31°C, compared to the 29/26°C regime. However, the highest reduction was for yield