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Defense Function of Spodoptera Litura Epidermis Against Nomuraea Riley Infection

Author: YuHaiYong
Tutor: YinYouPing
School: Chongqing University
Course: Biology
Keywords: Spodoptera litura Levin 's Nomura bacteria Biological Control Pathogenic mechanism
CLC: S476.12
Type: Master's thesis
Year: 2011
Downloads: 42
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Abstract

The entomopathogenic fungi important factors controlling pest populations nature, the body wall of invasive fungal infection insects main ways. Therefore, in addition to the infection ability of the pathogenic fungus itself, the structure and chemical composition of the insect body wall directly affect the efficiency of fungal infestation. The strains CQNr01 in our laboratory from diseased Spodoptera litura the stiff worm on an isolated entomopathogenic fungi, early studies have shown that the strains of the young larvae of Spodoptera litura better insecticidal effect, but old larvae infestation The lower rate. In order to explore the potential for the development and application of the strain, the subject is based on the biological characteristics of the strains, culture conditions, research dealt with different infection methods instars of S. litura larvae of different treatment under CQNr01 strain on the Spodoptera litura instar larvae virulence differences in the infection process of Spodoptera litura instar larvae the epidermal lipid germination of spores CQNr01 impact to do a preliminary study aimed to explore the epidermis of Spodoptera litura defense function and mechanism defense CQNr01 strains infect, a clear interaction between pathogenic fungi and Spodoptera litura provide a theoretical basis for biological control. The main findings of the study are as follows: the observed morphological and biological characteristics of the strains, combined with ITS sequence comparison results to determine the taxonomic status of the strains of the Leydig Nomura bacteria (Nomuraea riley), and named strains CQNr01. Biological research to determine the the suitable foundation the strains CQNr01 growth medium SDAY medium to determine the optimum temperature for mycelial growth and sporulation of 25 ° C, the optimum pH of 6.5; also the strain extracellular protease and chitinase ability to do research, found that poor bacteria chitinase production capacity, while the the strong protease production capacity of 25 ℃. The spore suspension soaked and injection two methods determined by the virulence differences of the strains CQNr01 conidia on 2nd instar larvae of Spodoptera litura. Soaking treatment Spodoptera litura, 1 × 10 ^{to 8 spores · mL ^{-1 concentration, age 2 and 4 larvae mortality were 89.98% and 13.33%; same The concentration of the bacterial suspension for injection treatment, age 2 and 4 larvae mortality to reach 100% and 88.89% respectively. Proved Elderly larval body wall the defense CQNr01 infection plays a decisive role. The spore suspension production instars of S. litura larvae in vitro epidermis and inoculated CQNr01 of using the fluorescence microscopy and scanning electron microscopy of spore germination and infection structure. Fluorescence observed the strains CQNr01 the spores be able to successfully attached to the larvae of Spodoptera litura vitro epidermis, but better than the fourth instar larvae spores in the 2nd instar larvae epidermal adhesion ability; inoculated 24h from the two age vitro epidermal on both started the phenomenon of spore germination and appressorium and germ tube produce germ tube growth and as the inoculation time constantly elongation, but under the same inoculation time spore germination rate and appressorium production quantity obvious in the 2nd instar larvae epidermal More than 4th instar larvae epidermis. Inoculated 24h and 26h, age 2 and 4 instar larval body surface observation of the scanning electron microscope, 24h 2nd instar larvae epidermal spore germination appear for 36 h increased the number of spore germination, germ tube continues to elongate ; larvae epidermis basically did not find the phenomenon of spore germination. To Spodoptera litura instars surface lipid ingredient is extracted, the extract process CQNr01 spores, then cultured in the medium of water agar medium and SMAY of to observe the treatment of epidermal lipids by instars larvae spores to germination, found in the oligotrophic water agar medium, the the epidermal lipid components can be strain growth of CQNr01 spore germination of the use of lipid components display the strain CQNr01 spore germination in a nutrient-rich medium inhibited, and the the 4th instar epidermal extract inhibitory effect more apparent. Conclusion: Leydig the the Nomura bacteria CQNr01 mycelial growth and sporulation of the optimum temperature of 25 ° C. The optimum pH value of 6.5. Old larvae of Spodoptera litura larvae infection capacity reduction is mainly influenced by the insect body wall structure and epidermal components. The young larvae epidermis more conducive to the the spores infect structure generation and invasive, old larvae epidermis is not conducive to spore attachment and infection structure formation. When nutritional deficiencies, S. litura larvae epidermal lipid composition can be strain CQNr01 spores growth germination utilized; while providing the nutrition they need to grow, spores selective medium easier use of nutrients, lipids The components of the spore germination overall inhibition.}}

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