SUSCEPTIBILITY OF SUGARCANE VARIETIES TO TWO SPECIES OF ROOT-KNOT NEMATODE (MELOIDOGYNE JAVANICA AND M. INCOGNITA), AND IMPLICATIONS FOR CROPS GROWN IN ROTATION WITH SUGARCANE

THE MULTIPLICATION of two species of root-knot nematode (Meloidogyne javanica and M. incognita) on tomato and 13 varieties of sugarcane was assessed by inoculating potted plants with 4000 nematode eggs and later measuring the number of nematodes present on roots and in soil. Fifty days after inoculation with M. javanica, there were 970 000 nematodes/pot on tomato and only 81 850 nematodes/pot on sugarcane (averaged across all varieties). The corresponding figures with M. incognita were 1 340 000 for tomato and 7720 for sugarcane. This result indicates that sugarcane is much less susceptible to root-knot nematode than tomato, a highly susceptible host. Ninety days after inoculation, nematode population densities on most sugarcane varieties had increased 80–126 times for M. javanica and only 1–10 times for M. incognita, indicating that sugarcane is more susceptible to the former species. Varieties varied considerably in their capacity to host both nematode species, as there was almost a 10-fold difference in final population densities between the most susceptible and resistant varieties. No variety was resistant to M. javanica, but Q152 and Q158 supported much lower population densities than other varieties. Q138 and Q196A were relatively resistant to M. incognita. The implications of these findings for crops that are currently grown in rotation with sugarcane (e.g. vegetable crops, legumes and pineapples) are discussed.