Study on Sugarcane Smut

The pathogen and characteristics, infection cycle, occurrence regularity and damage symptoms of sugarcane smut were introduced in the paper. Moreover, the comprehensive prevention measures were proposed on the basis of planting disease-resistant species, strengthening cultivation managements to improve dis- ease-resistant ability of sugarcane, and adopting fungicide control as assistant measures. The study provided certain basis for reducing damages of sugarcane smut and imorovin yield and quality of sugarcane.

Occurrence of Major Diseases and Insect Pests in Medium-term Growth Period of Sugarcane and The Diseases Resistance Evaluation in Guangxi

To figure out major diseases and insect pests of sugarcane and sugarcane resistance to diseases,the occurrence of major diseases and insect pests on 11 main sugarcane varieties in eight sugarcane producing areas of Guangxi was investigated during the medium-term growth period of sugarcane in 2015,and field resistance to smut and mosaic diseases was evaluated. The results showed that the dead heart rate（ DHR） ranged from 0. 00% to 38. 55%; new-planting sugarcane of Guiliu 2 and ratoon sugarcane of Liucheng 05-136 suffered the most severe damage in Beihai city,and the DHR were 38. 55% and 37. 66%,respectively. The incidence rate of smut disease ranged from 0. 00% to 24. 89%. Ratoon sugarcane was more susceptible to smut than new-planting sugarcane among all investigated varieties. Variety ROC22 was most susceptible to smut,and performed moderate susceptibility. Guiliu 2 was the second susceptible and performed resistance,with the incidence rate of 7. 45%. The rest nine varieties had high resistance. Sugarcane mosaic disease occurred mildly in Guangxi,and the incidence rate ranged from 0. 39% to 7. 73%. ROC22,Guitang 42 and Guiliu 2 expressed moderate resistance and the rests exhibited resistance. Sugarcane in Nanning and Beihai suffered more severe damage than those in other producing areas. The field evaluation system of sugarcane resistance to borers was expected to be constructed. ROC22 was most susceptible to smut,compared with other main varieties. Mosaic diseases occurred lightly in Guangxi. Multi-location and multi-year observation are necessary for accurate evaluation of sugarcane resistance to smut and mosaic diseases.

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.