Effects of high grafting on tomato plants infected by Meloidogyne incognita and Ralstonia solanacearum

The root-knot nematode Meloidogyne incognita is known to increase the severity of bacterial wilt in many solanaceous crops. In Japan, several bacterial wilt-resistant rootstocks that have the M.incognita resistance (Mi) gene in their genome have been developed for tomatoes. In this study, we aimed to examine whether the presence of Mi gene-breaking M.incognita population affects the development of bacterial wilt in bacterial-wilt-resistant tomato rootstocks with Mi in their genetic background. We also aimed to examine the possibility of using high-grafted tomatoes to control bacterial wilt in plants infected by M.incognita. Our results indicate that the resistance to bacterial wilt was easy to break in usual-grafted tomato plants infected with M.incognita and that M.incognita enhanced the vertical movement of Ralstonia solanacearum in the bacterial-wilt-resistant tomato rootstocks. In addition, our results suggest that high grafting led to significantly less wilting in the plants infected by M.incognita than did usual grafting.