Isolation,Screening Of Nematicidal Actinomycetes And Identification Of A High Efficient Strain

Plant parasitic nematode is one of the important pathogens,which cause economic losses about hundreds billions dollars in agriculture and forestry every year.Currently,the control of plant nematode disease is mainly chemical nematicides control.However,the impact of nematicides on human and animal health as well as ecological environment damage is gradually limited,biological control has been developed to become as environmental friend to control plant parasitic nematodes.In this study,soil samples were collected from South China Agricultural University arboretum,Guangzhou Panyu Central Lake Park,Zhaoqing Xinghu National Wetland Park,Qingyuan Feilai Lake Wetland Park,Jiangmen Enping Town Bay Mangrove Wetland Park,Zhuhai Qi’ao Island Mangrove Wetland Park,Guangzhou Haizhu National Wetland Park,and Guangzhou University City nursery base,with pine wood nematode and root knot nematode as targets the main results are as follows:1.Pine wood nematode was used as the test material,and 12 hole cell culture plate was used for preliminary screening After 24 h,17 strains had a corrected mortality of more than 90%,accounting for 5%of the total tested strains;56 strains have corrected mortality of 70%～90%,accounting for 17%of the total;68 strains have corrected mortality of 50%～70%,accounting for 21%of the total;189 strains have corrected mortality of less than 50%,accounting for 57%.2.After diluting the fermentation filtrate of the active strain with a corrected mortality more than 90%of nematode,and then rescreening with pine wood nematode as the target,the corrected mortality has been significantly different after diluting twice.As a whole,9 strains with a corrected mortality of more than 50%,accounting for 53%,the adjusted mortality of HZSD8-1 with the strongest activity is 95.02%,and the adjusted mortality of MPJD6-4 with the worst activity is 35.85%.3.The second instar larvae of Meloidogyne incognita were tested in the fermentation filtrate of HZSD8-1.The lethal rates of original solution,diluted 2-fold solution and diluted 5-fold solution were 95.87%,86.42%and 63.19%,after 24 h,respectively.4.In order to verify the application potential of the strain,the tomato infected with Meloidogyne incognita was used as the experimental material in the pot experiment.The results showed that the root knot index of the control group was 81.25,the fresh weight of the root was 2.23 g,the plant height was 42.63 cm.The root knot index of the HZSD8-1 fermentation filtrate original solution group was 40.63,the fresh weight of the root was 2.54 g,the plant height was 45.25 cm,the control effect on the 2^ndinstar larvae of Meloidogyne incognita was 49.99%.The root knot index of the diluted 5-fold solution group was 62.50,the fresh weight of root was 2.26 g,the plant height was40.88 cm,the control effect on the 2^ndinstar larvae of Meloidogyne incognita was23.08%.5.The strain HZSD8-1 was identified by the insert method to observe the morphological characteristics of the colony and mycelium.Observed the culture characteristics of the colonies using Chass agar,glycerol-aspartic acid agar,inorganic salt starch agar,oatmeal agar,yeast powder-malt extract agar,PDA,nutrient agar,and measured the physiological and biochemical characteristics of carbon source utilization,gelatin liquefaction,starch hydrolysis,nitrate reduction,milk coagulation and peptoneization,H₂S gas and melanin production.Based on the sequence analysis of16S r DNA and phylogenetic tree was constructed,the strain HZSD8-1 was identified as Streptomyces spectabilis.