Effects on Meloidogyne incognita of chitinase, glucanase and a secondary metabolite from Streptomyces cacaoi GY525

Abstract

Streptomyces cacaoi GY525, isolated from liquid compost containing crab shell powder, produced a secondary metabolite 3-benzyl-1,4-diaza-2,5-dioxobicyclo[4.3.0]nonane (BDDB) and lytic enzymes including chitinase and β-1,3-glucanase. To examine the effect of the bacterial culture filtrate (CF) and BDDB on mortality of second-stage juvenile (J2) and hatch inhibition of Meloidogyne incognita, different concentrations of them were added in 24-well plates containing ca 250 eggs and 250 J2, respectively. With increasing concentrations of CF and BDDB mortality of J2 increased while hatch decreased. In pot trials, tomato plants were treated with the GY525 culture (SC), culture medium (CM), commercial nematicide (5% ethoprophos) (CN) and combination of CN and SC (CN+SC). Tap water (TW) was used as a control. During the experimental periods, growth of tomato plants treated with SC markedly increased compared with TW and CN treatments. After 7 weeks the number of egg masses in TW was over 220, while that in SC was around 40 per plant. Population of J2 in soil and the number of egg masses in plant roots in SC, CN+SC and CN were significantly lower than those in TW and CM. Our results suggest that S. cacaoi GY525 has potential as a biological control agent against root-knot nematodes.