Analysis of Occurrence and Mixed Infection of Sugarcane Bacilliform Virus Disease in Hainan Sugarcane-growing Area

[Objectives]The paper was to explore the occurrence and mixed infection of sugarcane bacilliform virus disease in Hainan sugarcane-growing area.[Methods]A total of 348 sugarcane leaf samples were collected from 7 sugarcane-growing areas in Hainan Province.Molecular detection of sugarcane bacilliform virus(SCBV)was carried out by PCR using specific primers.[Results]SCBV was detected in 244 out of 348 sugarcane samples,with an average detection rate of 70.11%.The highest detection rate was 76.66%in the Danzhou sugarcane-growing area,while the lowest was 57.14%in the Baisha sugarcane-growing area.The SCBV-positive samples were subjected to testing for SCYLV,SCSMV,SrMV,and SCMV,respectively.The results indicated that 106 out of 244 positive samples exhibited a single infection with SCBV,while 138 samples exhibited mixed infections with SCBV and other sugarcane viruses.The proportion of mixed infections among the SCBV-positive samples was as high as 56.56%.Among the various types of mixed infections,two-virus and three-virus mixed infections were the most prevalent.[Conclusions]SCBV has emerged as a significant threat to the secure production of sugarcane in the Hainan sugarcane-growing region.It presents an explosive infection in the Hainan sugarcane-growing region and frequently combines with other sugarcane viruses to infect sugarcane.The findings of this study will provide a theoretical foundation for the prevention and control of sugarcane bacilliform virus disease.

Isolation,Screening and Identification of Antagonistic Actinomycetes against Ustilago scitaminea Syd

[Objectives] This study was conducted to obtain actinomycetes strains having antagonistic effect on Ustilago scitaminea Syd.[Methods] At first, actinomycetes strains were isolated from 22 soil samples in Hainan sugarcane regions. Then, antagonistic actinomycetes against U. scitaminea were screened by confrontation culture. Finally, the taxonomic status of antagonistic actinomycetes was determined using 16S rDNA.[Results] From the 22 samples, 984 actinomycetes strains were isolated. From all the isolated strains, 23 antagonistic actinomycetes strains were obtained through primary screening, and one strains with better antagonistic effect was then obtained through secondary screening, and designated FAS. 16S rDNA identification showed that strain FAS shared 99% sequence similarity with Streptomyces cealestis US24. A phylogenetic tree was built with MAGE 7.0 software, and the results showed that strain FAS had the shortest genetic distance with S. caelestis US24. Therefore, the actinomycetes FAS was determined as S. caelestis .[Conclusions] This study provides a new biocontrol method for the biological control of sugarcane smut, thereby ensuring sustainable development of sugarcane industry and sugar industry.

Optimization of Streptomyces caelestis Culture Conditions and Preliminarily Determination of Its Antifungal Components

Streptomyces caelestis FAS is an actinomyces strain isolated with Ustilago scitaminea as an indicator. With GAUZE s medium as the basic medium, carbon source and nitrogen source in the medium and ventilation volume were optimized, and the antifungal substances produced by S. caelestis FAS were preliminarily determined through organic solvent extraction and ammonium sulfate precipitation. The results showed that the antifungal components produced by S. caelestis FAS were proteins, and the optimal culture conditions were using corn flour as carbon source and KNO 3 as nitrogen source and culturing in 250 ml triangular flask added with 70 ml of culture medium. The crude protein obtained under these culture conditions had the best antifungal effect with an inhibition zone diameter of 25 mm. This study will provide a scientific basis for further study on the antifungal mechanism and application of S. caelestis FAS.

Study on Wide Antifungal Property of Bacillus subtilis HAS

Bacillus subtilis HAS is a biocontrol strain with better inhibitory effect on Sporisorium scitaminea Sydow. In order to further understand its action range,with fungal pathogens in sugarcane production as targets,confrontation tests and tests of inhibitory effect of secondary metabolites on growth of pathogens were carried out. The results showed that B. subtilis HAS not only had better inhibitory effect on S. Scitaminea,but also inhibited the growth of various fungal pathogens in sugarcane production. The inhibitory effect was the best on Ceratocystis adiposum,Thielaviopsis paradoxa,Fusarium moniliforme and Colletotrichum fuleatum,which was reflected by the radius of inhibitory zone over 10 mm. The inhibitory rates of the secondary metabolites were about 70%. It indicates that B. subtilis HAS has wide antifungal property,providing reference for further application of this strain.