Study On Diversity Of Pine Wood Nematode Associated Bacteria And Its Potential To Preserve Mulberry Fruit

Pine wood nematode disease,known as "pine cancer",spreads rapidly and is difficult to be effectively controlled.In recent years,the synergism of pine wood nematode and its associated bacteria has been the focus of research on the pathogenesis of the disease.Biological preservation is an important research direction of green preservation of agricultural products.The variety of associated bacteria of pine wood nematodes is beneficial to the screening of antagonistic bacteria that can be used for mulberry preservation and provide a diversified space for the research on biological preservation of mulberry after harvest.In this paper,various methods such as culture and isolation of microorganisms under different conditions,biology eco-plate analysis,16 s r RNA molecular sequencing,and metagenomics were explored.The effects of some associated bacteria strains on the long-term survival of pine wood nematodes were observed.1.Pine wood nematodes carry a large number of bacteria.From different types of media,each nematode can separate cfu with differences of 25208(PDA separation)?38000(NA separation).After the oscillating cleaning,the associated bacteria were shed off from the pine wood nematode body in large quantities,and each of the bacteria was between 1381 and 2660 cfu.2.The complete sequence sequencing of 16 s r RNA was used to identify 82 associated bacteria from 140 isolated strains,of which Pseudomonas sp accounted for nearly half(45%)(37 strains).Other strains are: Enterobacter sp accounted for 7.3%,Flavobacterium sp accounted for 6.1%,Janthinobacterium sp accounted for 6.1%,Pantoea sp accounted for 4.9%,Bacillus sp accounted for 4.9%,Stenotrophomonas sp accounted for 4.9%,Leclercia accounted for 4.9%,Rahnella sp3.7%,Massilia Sp 2.4%,Antarctic 2.4%,other less dominant strains are Brevundimonas sp,Acinetobacter sp,Pedobacter sp,Buttiauxella sp,Duganella sp,Rouxiella,etc.,accounting for about 1.2%.The associated bacterial groups isolated by different media and pine wood nematode treatment all showed overlap and differences,which also affected the proportion of their gram staining properties,but pseudomonas could be isolated under various treatment combinations.3.The metagenomic sequencing of the associated bacteria of pine wood nematodes revealed that 77% of the surface of pine wood nematodes were unidentified strains,and the remaining 23% were mainly pseudomonas,followed by Epilithonimonas sp.,Sphingomonas Sphingomonas sp.Acinetobacter,larne,short-wave monomonas and clostridium difficile were the secondary dominant strains,and the biological ecological plate showed that there were different physiological and biochemical types of the strains with different overlap degree,which may come from their classification attributes or physiological and biochemical similarities and differences.4.Through the observation of the number of survival period of pine wood nematode and associated bacteria in the wood segment,the bacteria had a certain influence on the long-term survival of pine wood nematode.5.The preservative effect of associated bacteria on mulberry was studied.9 kinds of associated bacteria were used to preserve mulberries.Through observing the changes of weightlessness rate,rot rate,Vc content and other indexes,the selected strains limited by the number of samples had no obvious preservative effect on mulberries.The above results especially showed the diversity and quantity of bacteria carried by pine wood nematodes.