In vitro bioassay of Purpureocillium lilacinum and Bacillus thuringiensis for control of Meloidogyne incognita on black pepper (Piper nigrum L.) in Sarawak, Malaysia, Northern Borneo

This study aimed to evaluate strains of the entomopathogenic fungus Purpureocillium lilacinum and the bacterium Bacillus thuringiensis from Bintulu, in north-eastern Sarawak, Malaysia for their in vitro nematicidal properties against different developmental stages of Meloidogyne incognita. Ten indigenous novel strains of P. lilacinum, a commercial strain of the fungus (P. lilacinum M), and a strain of B. thuringiensis carrying Cry6 and Cry14 gene sequences were screened for parasitism against M. incognita females and eggs, egg hatching inhabitation and 2^nd stage of active juveniles (J2) mortality. Our study demonstrates that P. lilacinum A and P. lilacinum B were the most effective biocontrol agent against M.incognita females, eggs and J2 due to highest infection of females, eggs and significant decrease in egg hatching events. P. lilacinum A, P. lilacinum B, and P. lilacinum M (positive control) demonstrated highly significant infection (>90%, P≤0.01) on M.incognita female nematodes. The present study revealed that spore suspension (10⁵ spore/mL) of P. lilacinum A, P. lilacinum B and P. lilacinum M resulted in 78.8%, 66.0% and 73.4% parasitism on eggs, respectively. P. lilacinum A, P. lilacinum B and P. lilacinum M with low mortality of 6.0%, 5.5% and 5.7%, respectively, showed significant (P<0.05) differences in mortality effect on J2 of M.incognita as compared with control treatment (2.3%). Hatching of M. incognita eggs incubated in spore suspension of P. lilacinum A, P. lilacinum B and P. lilacinum M for seven days were reduced by 89% when corrected for control mortality (26%).