STUDIES ON THE POSSIBLE ROLE OF PLANT HOST ON THE DEVELOPMENT OF ROOT-KNOT NEMATODE, MELOIDOGYNE JAVANICA AND PASTEURIA PENETRANS AS AFFECTED BY DIFFERENT HARVESTING DATES

Abstract

There were strong interactions between plant-hosts and Pasteuria (P<0.01) on numbers of eggmasses, root galling and numbers of eggs/eggmass produced by females of Meloidogyne javanica after 422, 595 and 767 degree days after first, second and third harvests. The presence and absence of the biocontrol agent (Pasteuria penetrans) in the treatments influenced these parameters and it was also influenced by plant hosts. After the first harvest, there were significant differences in the above-mentioned parameters between P. penetrans and control treatments (P<0.01). There was lesser root galling (3.13) in the treatments where P. penetrans was applied compared with untreated control (5.53). Plant hosts also differed significantly in root galling (P<0.01) and the interaction between plant-host and Pasteuria was non-significant (P>0.05). After the second harvest, there were significant differences between Pasteuria and control treatments in these parameters. Plant-hosts differed significantly in numbers of eggmasses and root galling (P<0.01) and there was no interaction between plant-host and Pasteuria (P>0.05) regarding eggmasses and root galling. After the third harvest, there were significant differences between Pasteuria and control treatments in the production of eggmasses (P<0.01), root galling, and the number of eggs/eggmass (P<0.01). There were fewer eggmasses (379) and lesser galling (5.1) in the treatments where P. penetrans was applied. Plant-hosts differed significantly in numbers of eggmasses and root galling (P<0.01). However, there was no interaction between plant-host and Pasteuria (P>0.05) regarding eggmasses and root galling. Contrarily, a significant interaction between plant-hosts and Pasteuria (P<0.01) and greater numbers of eggs were observed among females developed on tomato in the presence (385) and absence (629) of Pasteuria. The rate of parasitism of M. javanica was very low and there was no P. penetrans infection after 422-degree days as neither vegetative stages nor mature endospores were observed in females. After 595-degree days, few females were observed having vegetative stages of the bacterium. The parasitism of females was only observed though very low after 767-degree days and females reared on okra were infected in greater numbers than those reared on tomato and eggplant.