Studies On The Biology And Formulation Of Pochonia Chlamydosporia 152 Strain

Pochonia chlamydosporia is an important biocontrol fungi against plant parasitic nematodes. It's potentiality in nematode control is due to producing chlamydospore. In order to obtain more information about P. chlamydosporia 152 strain, its biological characteristic, sporulation conditions, fermentation conditions and formulation , as well as the bioefficacy to plant, were studied. The results are listed as follows:P. chlamydosporia 152 strain growed well on the PSA , CMA and Czapek media, the colony diameter was 5.95cm, 6.00cm and 6.10cm respectively for 15 days at 28℃.P. chlamydosporia 152 strain was measured in vitro for pathogenicity to eggs, egg masses and females of Meloidogyne incognita on water agar. The results showed that the parasitism percentage was 92.50%, 86.2% and 98.65% respectively. Infected eggs were full of hyphae, aberrant or wrinkled, the embryo was destroyed. The fungi could colonize on egg mass surface and gelatinous matrix, as well as the eggs in intact egg mass. The females were also parasitized, and the infected body was shrunken. In vitro test, the percentage of colonization to plant root segment was up to 80%, and the CFU in plant rhizosphere soils was 4.30×10⁶ cfu·g^-1 after 30 days.In order to obtain more information about fungi sporulation,a two-stage cultivation method was used to determine nutritional and environmental conditions affecting chlamydospore production of P. chlamydosporia 152 strain. Chlamydospore production of PC152 strain was the hightest when the Czapek medium contained 3.00 g·L^-1C , a C:N ration of 2.5:1, sucrose/ NaNO3 as the carbon and nitrogen sources, and pH8. Sporulation was enhanced by 1.00% NaCl(W/V). Absence of the macroelement, especially element P, could enhance sporulation of PC152 strain .Optimal liquid fermentation conditions for P. chlamydosporia 152 strain were studied, the results were as following:3.0%(W/V) shrimp shell meal as culture medium, the initial pH4.0⁷.0, inoculum volume 1/10(V/V), 200mL liquid medium per 500mL triangular flask , 28℃, 150 r·min^-1 shaking culture. P. chlamydosporia 152 strain could grow well in 10-Liter liquid fermentor, the conidia density were up to 1.82×10⁸ spores·mL^-1 for 72h. By means of single factor and orthogonal experiments, the optimal conditions of chlamydospore production for solid-state fermentation were obtained as following: the proportion of corn meal(270≤φ≤550) to juncao and material to water were 7:3(g/g) and 1:0.5(g·mL^-1) respectively, sucrose 1.5%, NaNO3 0.85%, NaCl 1.0%, fermentation liquor for 48⁶0h as spore inoculum, inoculum volume 0.50 mL·g^-1,the initial pH7.0⁸.0. By diphasic fermentation and under this optimal fermentation conditions, the chlamydospore density could reach 1.50×10⁶ spores·g^-1 and the conidia density were up to 4.00×10⁹ spores·g^-1 for 10 days.Based on assaying adjuvants compatibilities to P. chlamydosporia spores, the carrier diatomite, wetting agent Tween-80, dispersant PEG6000 and UV protectants folic acid were obtained. By orthogonal experiments, based on wetting efficiency and suspensibility of P. chlamydosporia PC152 strain formulation, the wettable powder of P. chlamydosporia was developed. It included 5% Tween-80, 5% PEG6000, 0.90% folic acid, 45% diatomite and 44.1% spore powder. The spore density of P. chlamydosporia WP was 3.28×10⁹cfu·g^-1, wetting time was 29.81 s, suspension rate was 75.80%.The results from pot test showed that P. chlamydosporia WP could control the tomato RKN disease and the water spinach RKN disease, and the control effects were 70.59% and 71.43% respectively. The results also indicated that P. chlamydosporia could colonize and grow on the plant rhizosphere and the CFU in rhizosphere soils was 4.30×10⁶ cfu·g^-1 for 60 days.