Differential feeding site development and reproductive fitness of Meloidogyne incognita and M. javanica on zucchini, a source of resistance to M. incognita

The development of Meloidogyne incognita and M. javanica on zucchini ‘Amalthee’ was compared to characterise critical events in plant parasitism. Meloidogyne incognita was much less successful parasitising zucchini than M. javanica despite similarities in penetration rates and juvenile development. The increased frequency of undersized individuals, immature females and empty galls evidenced a failure in M. incognita development. Meloidogyne incognita induced larger feeding sites that contained more and larger giant cells than did M. javanica. Malformation of the M. incognita giant cells and abnormal growth of the surrounding tissues was observed at both 11 and 25 days post-inoculation. Critical events in parasitism differentiating the nematode isolates were the transition from fourth-stage juveniles to females, and the reduced fertility of the egg-laying females. Zucchini can be considered a source of resistance to M. incognita because it restricted nematode proliferation by supporting less fertile egg-laying females and producing fewer egg masses and total eggs.