| There are many insects in nature that can spin cocoons and metamorphosis inside.As a model organism in Lepidoptera Bombycidae,silkworm(Bombyx mori)has the largest feeding amount and the most economic valuein.However,it is often attacked by pathogenic microorganisms,which threaten the sericulture.Fungus is one of the main pathogens,the fungal diseases of silkworm mainly include White muscardine,Green muscardine,Yellow muscardine,Aspergillosis,etc.Among them,White muscardine is the most common with high harm,and it is very easy to be diffused.Therefore,we want to find an effective and safe antifungal drug to reduce the harm of White muscardine to sericulture.We used Jingsong × Haoyue silkworm as experimental materials than we found that Terbinafine Hydrochloride(TFH)can prolong the survival time of silkworm infected with B.bassiana,Then,we conducted an in-depth study on the TFH,The minimum inhibitory concentration of the TFH on B.bassiana in vitro and the optimal therapeutic concentration for White muscardine in silkworm were screened,and the safety of the TFH was evaluated by investigating its effects on the physiological growth,cocoon quality and intestinal microorganisms of silkworm.The main results are as follows: 1.TFH has antibacterial effect on B.bassiana in vitro and has therapeutic effect on White muscardine in silkwormTFH has a minimal inhibitory concentration(MIC)of 25?g/ m L on B.bassiana in vitro,and also has an inhibitory effect on the growth and reproduction of B.bassiana in silkworm,within a certain concentration range,as the concentration increase of TFH the survival time of infected silkworm is gradually extended,and the best therapeutic concentrationt is 95?g/m L.2.Effects of TFH on growth and cocoon quality of silkwormBy investigating the changes of silkworm weight in the fifth instar of different treatment groups,it was found that the weight of silkworm in the TFH experimental group was not significantly changed compared with the control group,and no significant difference was observed in the sensory evaluation.The results of cocoon quality investigation showed that,compared with the control group,the weight of cocoon,the percentage of cocoon weight,and the weight of pupa and cocoon of three different TFH test groups were decreased,but the difference was not significant.3.Effects of TFH on intestinal microorganisms of silkwormUsing the 16 Sr DNA gene amplification technique,the intestinal microbial composition of silkworm 5th larva was analyzed on Illumina Novaseq high-throughput sequencing platform after feeding 3 and 4 days respectively.The results showed that the silkworms fed 95?g/m L TFH and 0.1% DMSO on the third day of the experiment had similar diversity and relative abundance of intestinal microbial species at the phylum and genera levels compared with normal silkworms.The diversity and relative abundance of intestinal microbial species are similar at the phylum level and genus level.Firmicutes,Proteobacteria,Acidobacteria and Actinomycetes were the main groups at the phylum level.The abundance of Enterococcus,Sphingomonas,Pseudomonas,Stibactobacter and Brevundimonas are highest in genus level.On the fourth day of the experiment,the relative abundance of intestinal microflora in each group changed greatly at the level of phylum,The species diversity and relative abundance at genus level were changed in varying degrees.Enterococcus was still the main intestinal flora in each group,but the relative abundance of 95g/m L TFH group and 0.1% DMSO group were significantly reduced,meanwhile the Cuprobacter became one of the dominant bacteria in the intestine of silkworm blank control,the relative abundances of Ralstonia and Brevundimonas were increased in 0.1% DMSO control group while the relative abundances of Pseudomonas were decreased.In addition,we detected 12.20% Enterobacteriaceae unclassified in 95g/m L TFH group. |
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