Control Effect of Validamycin against Seedling Blight of Atractylodes macrocephala

[Objective] The paper was to explore the effective agent against seedling blight of Atractylodes macrocephala. [Method] The control effects of 60% validamycin A SP against seeding blight of A. macrocephala were studied in the field, and compared with that of control agent 20% bismerthiazol WP. [Result] At 14 d post the third spraying, the control effect of 60% validamycin A SP at the dose of 495-540 g/hm^2 was 76.9%,which was equivalent to that of control agent 20% bismerthiazol WP sprayed at the dose of 270 g/hm^2(76.7%). [Conclusion] 60% Validamycin A SP could be used as the ideal agent against seedling blight of A. macrocephala, with good prospects of application and popularization.

Efficacy Evaluation of 16% Validamycin·thifluzamide SC against Selerotium rolfsii in Dendrobium officinale Kimura et Migo

[Objective] The paper was to understand the control efficacy and the optimal dosage of 16% validamycin？thifluzamide SC on controlling Selerotium rolfsii in Dendrobium officinale Kimura et Migo. [Method] The control efficacy of 16% validamycin·thifluzamide SC against S.rolfsii was determined by spraying agents on the whole plant of D.officinale. The significance of differences was analyzed by Duncan＇s new multiple range test （DMRT）. [Result] The control efficacy of 16% validamycin.thifluzamide SC sprayed at the doses of 80-160 mg a.i./kg was 85.33% at 14 d post spraying, higher than that of control agent 4% validamycin AS sprayed at the dose of 80 mg a.i./kg （78.36%）, and equivalent to that of control agent 240 g/L thifluzamide SC sprayed at the dose of 120 mg a.i./kg （90.60%）. [Conclusion] 16% Validamycin·thifluzamide SC sprayed at the doses of 80-160 mg a.i./kg could effectively control the damage of S.rolfsii in D.officinale, and could be popularized in the production.

Capillary Electrophoretic Determination of Jinggangmycin A in Formulations Using Direct UV Detection

A simple, fast and reliable method was developed for the analysis of jinggangmycin A （validamycin A） in commercial formulations. The running buffer used was acetate buffer （100 mmol/L, pH 4.7） with 15 kV as the applied voltage. The detection was achieved by using direct UV mode at 200 nm and the detection limit was 0.2 μg/mL. Linearity in the concentration range of 5-500 μg/mL was excellent （RE 〉 0.999）. The run-to-run repeatability （n = 3）, as expressed by the relative standard deviation （RSD） for migration times and peak areas were less than 0.5% and 3.0% respectively. The mean recovery ranged from 97.2% to 101.4%.

Integrated Approach to Control False Smut in Hybrid Rice in Sichuan Province, China

Severe epidemic of false smut, caused by Ustilaginoidea virens （Cooke） Takahashi （teleomorph Villosiclava virens） has been reported in different parts of Asia and America. Different fungicides or bio-control agents against false smut were applied at different times before heading on a susceptible rice variety Pu-6. A control efficiency as high as 91.92% was resulted from spraying 2.5% Wenquning, a suspension of Bacillus subtilis in solution of validamycin with 4.5 L/hm2 at 6 d before heading. Among the 186 hybrid rice screened in 2010, low significant correlations between the dates of full heading, rates of infected plants and panicles as well as the number of infected florets were found, with the correlation coefficients ranging from 0.2331 to 0.5212. However, significant difference in susceptibility coefficients was also found between the varieties which had the same dates of full heading. In the plot experiments to compare the susceptibility in 2011, the average rates of infected panicles of Yixiangyou 2168, Chuanxiangyou 3, Dexiang 4103, Yixiangyou 2115, Nei5you 317, Yangxinyou 1 were significantly lower than those of the control varieties Gangyou 725 and Gangyou 188 at the disease nursery located at Qionglai, Sichuan Province, China. When Neixiangyou 8156 and Nei5you 317 were sprayed with 2.5% Wenquning at 4.5 L/hm2 for two times at 6 d before and 1 d after heading, respectively, the control efficiencies of Nei5you 317 and Neixiangyou 8156 were respectively 100% and 82.24% compared to that of Gangyou 725. Satisfactory control effects had also obtained by single spray of 2.5% Wenquning at 4.5 L/hm2 at 5-6 d before heading. Therefore, less susceptible hybrid rice in combination with spraying Wenquning at 5-6 d before heading was suggested for the disease control in Sichuan Province, China.

Validamycin treatment significantly inhibits the glycometabolism and chitin synthesis in the common cutworm,Spodoptera litura

Validamycin,as a broadly applied antibiotic,has been used to control rice sheath blight disease.Furthermore,validamycin was considered as an insecticide to control agricultural pests.Insight into the mechanism of validamycin’s action on insects can provide molecular targets for the control of agricultural pests.In this study,a toxicological test analysis revealed that Spodoptera litura larval growth and development was significantly inhibited and the pupation rate was significantly reduced with the increase of the concentration of validamycin.According to the NMR-based metabolomic analysis,a total of 15 metabolites involved in glycolysis and tricarboxylic acid cycle(TCA)pathways were identified.Additionally,trehalase activities,glucose and chitin contents were significantly downregulated,but the trehalose content was upregulated after exposure to validamycin.Reverse transcription quantitative PCR analysis revealed that the expression level of genes involved in glycolysis,TCA and chitin synthesis were upregulated after treating with validamycin.Further chitin staining also confirmed that chitin content was downregulated at 12 h after validamycin treatment.Our results indicated that validamycin worked via two different molecular mechanisms,one through inhibiting glycometabolism and the other by inhibiting chitin synthesis in S.litura.The information lays a theoretical foundation for further control of S.litura.

Integrated transcriptome sequencing and RNA interference reveals molecular changes in Diaphorina citri after exposure to validamycin

Validamycin has been widely used as a specific competitive inhibitor of tre-halase.In our previous research,validamycin significantly inhibited trehalase activity and chitin synthesis in Diaphorina citri,resulting in abnormal phenotypes.However,the mechanism of validamycin's action on D.citri remains unclear.Here,using a comparative transcriptome analysis,464 differentially expressed genes(DEGs)in D.citri were identified after validamycin treatment.A Gene Ontology enrichment analysis revealed that these DEGs were mainly involved in“small molecule process”,“structural molecule ac-tivity”and“transition metal ion binding”.DEGs involved in chitin metabolism,cuticle synthesis and insecticide detoxification were validated by reverse transcription quantitative polymerase chain reaction.The RNA interference of D.citri chitinase-like protein EN03 and D.citri cuticle protein 7 genes significantly affected D.citri molting.Moreover,the recombinant chitinase-like protein EN03 exhibited a chitin-binding property,and an antimicrobial activity against Bacillus subtilis.This study provides a first insight into the molecular changes in D.citri after exposure to validamycin and identifies two effective RNA interference targets for D.citri control.

Inhibition of trehalase affects the trehalose and chitin metabolism pathways in Diaphorina citri(Hemiptera:Psyllidae)

The Asian citrus psyllid,Diaphorina citri is the principal vector of huanglongbing,which transmits Candidatus Liberibacter asiaticus.Trehalase is a key enzyme involved in trehalose hydrolysis and plays an important role in insect growth and development.The specific functions of this enzyme in D.citri have not been determined.In this study,three trehalase genes(DcTreJ-1,DcTrel-2,and DcTre2)were identified based on the D.citri genome database.Bioinformatic analysis showed that DcTrel-1 and DcTrel-2 are related to soluble trehalase,whereas DcTre2 is associated with membrane-bound trehalase.Spatiotemporal expression analysis indicated that DcTrel-1 and DcTrel-2 had the highest expression levels in the head and wing,respectively,and DcTre2 had high expression levels in the fat body.Furthermore,DcTrel-1 and DcTrel-2 expression levels were induced by 20-hydroxyecdysone and juvenile hormone III,but DcTre2 was unaffected.The expression levels of DcTrel-1,DcTrel-2,and DcTre2 were significantly up-regulated,which resulted in high mortality after treatment with validamycin.Trehalase activities and glucose contents were downregulated,but the trehalose content increased after treatment with validamycin.In addition,the expression levels of chitin metabolism-related genes significantly decreased at 24 and 48 h after treatment with validamycin.Furthermore,silencing of DcTrel-1,DcTrel-2,and DcTre2 reduced the expression levels of chitin metabolism-related genes and led to a malformed phenotype of D.citri.These results indicate that D.citri trehalase plays an essential role in regulating chitin metabolism and provides a new target for control of D.citri.