Resistance screening of tomato cultivars to Meloidogyne incognita and M. javanica populations from Ethiopia

Soil and root samples were collected from major tomato growing areas of Ethiopia during the 2012/2013 growing season. Meloidogyne species were identified using DNA based identification techniques. Meloidogyne incognita and M. javanica were found to be the predominant root-knot nematode species across the sampled areas. The aggressiveness of the different populations of these two species were tested on two susceptible tomato cultivars (Marmande and Moneymaker). Of each species, the two most aggressive populations (‘Jittu’& ‘Babile’ for M. incognita and ‘Jittu’ & ‘Koka’ for M. javanica) were further used to screen fourteen commercial tomato cultivars (ARP-Tomatod2, Bishola, Chalie, Cochoro, Eshete, Fetane, H-1350, Marglobe, Melkasalsa, Melkashola, Metadel, Miya, Moneymaker and RomaVF) commonly used in Ethiopia. Cultivar Marmande was used as a susceptible control. The resistance screening was done by inoculating 30 individual seedlings (4-leaf stage) of each cultivar with 100 freshly hatched second-stage juveniles (<24hrs). Plants were grown in plastic tubes (66ml volume) and kept in a growth chamber in a completely randomized design. Seven weeks after inoculation the number of egg masses produced on each cultivar was assessed. For all populations egg masses were found on each cultivar. The M. incognita ‘Jittu’ population was consistently aggressive across all the cultivars tested in comparison with the other three populations. Lower numbers of egg masses of both populations of M. incognita and population Jittu of M. javanica were produced on the cultivars RomaVF and Chochoro. For M. javanica population Koka the lowest number of egg masses was observed on cultivars Melkashola and Marglobe. On several plants of these cultivars no egg masses of M. javanica population Koka were detected indicating possible resistance. Even though complete resistance was not found from this study there is a potential that a few cultivars viz Chochoro (a cultivar largely used by Ethiopian small scale farmers), Melkashola and Roma VF could perform well if they are crossed with tomato cultivars with Mi gene. Further assessment of the resistance mechanism will generate important information for local breeding programmes.