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Efficacy of Trichoderma spp. in Controlling Root-knot Nematode (Meloidogyne incognita)
Dissertation Abstract:
Six species of Trichoderma (T. piluliferum, T. hamatum, T. harzanium, T. longibrachiatum, T. aureoviride, and T. koningii) irradiated with ultraviolet (UV) light for various times including 0, 5, 10, 15, 30, 45, and 60 minutes were tested for the efficacy in parasitizing eggs of root-knot nematode (Meloidogyne incognita). Three species, namely: T. piluliferum, T. hamatum, and T. harzanium, which were exposed to UV for 30 minutes provided the percentage of infectivity of 49.48, 30.45, and 28.25, respectively. Wildtypes and mutants from each species of Trichoderma selected from those with highest percentage of infectivity were transferred to PDA and PDA supplemented with benomyl (Benlate 50% WP) at the rates 5, 10, 20, and 40 ppm of active ingredients. Mutants from T. piluliferum and T. hamatum could grow on PDA and PDA supplemented with 5 and 10 ppm benomyl. T. harzanium (wildtype and mutant) could grow on 5-40 ppm benomyl. Amount of chitinase and cellulase enzymes were determined by enzyme activity and enzyme specific activity. T. harzanium (mutant and wildtype), T. piluliferum (mutant), and T. hamatum (mutant) could produce more chitinase than other species. Mutant of T. piluliferum could markedly produce more chitinase as compared to wildtype isolate. Enzymespecific activity of chitinase and cellulose, and enzyme activity of cellulase were similar to enzyme activity of chitinase.
The efficacy of the root-knot nematode control agent was tested under screenhouse and field condition with leaf lettuce. For screen house test, application of Trichoderma spp. at 3 rates 1, 2, and 4 g/pot indicated that application of T. piluliferum and T. harzanium at 4 g/pot provided more fresh shoot weight than other treatments. A slight difference of average fresh root weight could be seen. Populations of Trichoderma spp. were determined from 30 and 60 days after planting. T. harzanium and T. piluliferum were found to have the highest population in the soil. The second crop of this experiment was conducted by planting leaf lettuce after harvesting the first crop. The results from this crop were the same pattern except number of gall was one fold higher than the first crop by average. The results showed that T. piluliferum and T. harzanium should be selected for testing in the field conditions. The tests for Trichoderma application under field conditions were conducted as pot test at Klongsan, Bangkok and in two experimental fields at Kamphaengsaen Campus and Chonburi province. The results from all tests seemed to follow the same pattern of expression. T. piluliferum and T. harzanium gave higher fresh shoot weights, lower fresh root weights, lower numbers of galls, and higher populations in the soil when compared to control (M. incognita inoculation). A slight difference could be seen when Paecilomyces lilacinus was mixed with Trichoderma. This study showed that T. piluliferum and T. harzanium had a potential to control root-knot nematodes.