Preliminary Study On The Biological Characteristics Of Aschersonia Badia

Aschersonia is an important pathogen to control scale insects and whiteflies. However, it has never been reported that the biological characteristics of A. badia were studied. In this study, fungal preliminary investigations on the isolation, purification, strain identification, basic biological characteristics, medium optimization, and activity of secondary metabolites were carried out, which can lay the foundation for further research and development of this fungus.Specimen (briefly named GDSH-1) was collected from the city of Sihui in Guangdong Province and its morphological characteristics were obtained by morphological observation. The stroma, pycnidia and conidial characteristics were acquired by hand section. Stroma are discoid, orange to light brown, 1 to 3 dispersed orifice, surrounded by a wide and uniform yellow hypothallus, stoma diameter 1.2 mm, high-0.7mm. Pycnidia are elliptic, 441×277.5μm, from the top of stroma surface about 120μm. Paraphysises are present in pycnidia, 50.9 ~ 118.1μm in length. Conidia are fusiform or spindle-shaped, sharp at both ends, 10.0 ~ 13.0×1.2 ~ 2.0μm. Compared with reported Aschersonia, GDSH-1 was identified as Aschersonia bidia. Subsequently, ribosome large subunit (LSU rDNA) sequences of the strain were cloned and the length of the fragment is 1.03 kb, then the software of CLUSTALX was used to align homologous sequences obtained from GenBank. With the help of MEGA4.0 software, their phylogenetic tree and genetic distances were obtained. The results showed that the GDSH-1 was further confirmed as A. bidia.In this thesis, the effects of carbon sources, nitrogen sources, major elements, trace elements and vitamins on spore germination, mycelial growth and sporulation were studied. The results showed that sucrose and yeast powder were best for the growth, all major elements such as magnesium, iron, sulfur, phosphorus, potassium and so on are necessary for the growth. Zinc ion in trace elements can stimulate fungus growth but other members inhibit hyphal growth. Tested vitamins did not promote growth while showed contrary effects. Sporulation experiments indicated that glucose and yeast powder were best for spore conduction. All major elements were necessary for the sporulation, Mn2+,Ca2+,VB2 and VB6 increased sporulation. Soluble starch, L-glycine and casein could promote germination, Potassium and phosphorus among major elements were necessary for the germination, many microelements inhibited germination, VB4 and VB6 in vitamins could promote germination to different degrees. Optimization of medium by orthogonal test indicated that the best media for mycelial growth contained sugar (40g), yeast extract (7.5g), K2HPO4 (1.65g), FeSO4 (0.01g), MgSO4 (1.00g) and ZnSO4 (0.15g) per litre.Moreover, the influences of A. badia secondary metabolites on microbes were studied in the thesis and the results showed that they expressed somewhat bioactives against Bacillus subtilus, Escherichia coli and Saccharomyces cerevisiae.