Abstract
In the present study, we studied the biocontrol potential of Trichoderma harzianum (its teleomorph is Hypocrea lixii) against the root-knot nematode Meloidogyne javanica. T. harzianum used in this study was confirmed using the phylogenetic analyses of the LSU rDNA sequence. T. harzianum was grouped consistently with its teleomorph H. lixii in a highly supported clade within the family Hypocreaceae. Eggs treatment with H. lixii at 10(7) colony forming unit per mL (cfu/mL) infected 89.2% of eggs compared with 0.4% in the control. In addition, the fungus decreased the egg-hatching rate by 8.8%. Treatment of M. javanica second stage (J(2)) with culture filtrates of H. lixii caused 64.5% mortality of J2 in after 72 h of exposure. Under greenhouse conditions, all treatments reduced disease severity and enhanced plant growth compared with the untreated control. H. lixii reduced the number of galls (49), the number of egg masses (32.8), and the number of eggs per egg mass (399.8) compared to the inoculated control. Plant height, root length, and the fresh and dry plant weights were significantly reduced by infection with M. javanica; however, prior application of H. lixii prevented this reduction. Application of the fungus not only had a toxic effect on the nematode but also enhanced plant growth, supplying many nutritional elements and inducing systemic resistance in the plants. We demonstrated that application of H. lixii to the soil at a concentration of 106 or 10(7) cfu/mL is required for sufficient biocontrol of M. javanica.