Pathogenic variation among three major root-knot nematodes ( Meloidogyne spp.) affecting guava ( Psidium guajava L.) cv. Allahabad Safeda

The pathogenic potential of three root-knot nematodes, Meloidogyne enterolobii , M. incognita , and M. javanica on the guava ( Psidium guajava L.), cultivar Allahabad Safeda, was investigated in a greenhouse setting. The guava seedlings were inoculated with 0 (control), 100, 500, 1000, 1500, and 2000 s-stage juveniles (J 2 s) per plant. When compared to the control, nematode-inoculated plants showed significant differences in all three Meloidogyne spp., namely M. enterolobii , M. incognita , and M. javanica , in terms of growth parameters and nematode reproduction on the host plant. At 100 J 2 s and higher inoculum levels, such as 500, 1000, 1500, and 2000 J 2 s per plant, the reductions in growth were discernible compared to the control. As inoculum levels increased, root galling, egg mass production, and nematode populations all increased. The estimated soil and root populations of M. enterolobii and M. incognita gradually increased with increasing inoculum amounts. There was a noticeable increase in the population at all inoculum levels as compared to the lowest inoculum level (100 J 2 s). As the nematode inoculum increased, both the reproduction factor (RF) and multiplication factor (MF) decreased. The present study demonstrated that M. enterolobii is highly pathogenic, M. incognita is moderately pathogenic, and M. javanica is relatively less pathogenic to guava. At a minimum inoculum of 100 J 2 /plant, M. incognita can cause damage to guava by damaging the roots and inhibiting plant growth. At an initial population density of 100 J 2 s/plant of M. enterolobii , the guava crop suffers the most because of extensive multiple root galling and secondary infection by other soil-borne pathogens.