Oil cakes stimulate native population of Catenaria anguillulae that suppresses root-knot disease of cowpea

In the present investigation, oil cakes of linseed (Linum usitatissimum), mustard (Brassica juncea) and groundnut (Arachis hypogaea) were applied in a Meloidogyne incognita infested soil at a rate of 0.5% to examine their impact on the population dynamics of Catenaria anguillulae and its subsequent role in suppressing the root-knot in cowpea (Vigna unguiculata). The assessment of the population dynamics of the fungus following the application of the oil cakes at eight-day interval revealed the maximum stimulation (6.6 folds) in the native population of C. anguillulae 24 days after amendment of groundnut oil cake followed by linseed and mustard oil cakes. The stimulated native population of the fungus resulted in a significant reduction in the soil population of M. incognita juveniles (J₂s), and gall-index and getting the widest nematode-to-root biomass ratio (1:531) compared to the control (1:160, narrowest ratio). The population of other plant parasitic nematodes (PPNs) was also suppressed following the oil cake amendment. The suppressed population of M. incognita and other PPNs significantly improved the plant growth irrespective of the cakes. This is the first observation on establishing a relationship between the stimulated population of C. anguillulae and the suppression in the population of PPNs.