Gram-Positive Bacteria Associated with Rice in China and Their Antagonists Against the Pathogens of Sheath Blight and Bakanae Disease in Rice

It is necessary to understand the bacterial populations associated with rice so as to provide more information and natural resources for effective management of major diseases in rice. A survey on screening and identification of gram-positive bacteria was conducted during 1998 2004. Seven hundred and fifty-six rice samples were collected from Zhejiang, Jiangsu, Fujian and Yunnan Provinces, China. Over 1000 bacterial isolates were isolated and tested for colony morphology, pathogenicity, and some characteristics of bacteriology including Gram staining, fluorescent pigment on Kings medium B and microscopic observation for endospore. Together with five standard reference strains, 74 representative gram-positive bacterial isolates were confirmed by Biolog and gas chromatographic analysis of fatty acid methyl esters. Five bacterial species of Bacillus and other three genera were identified and isolates from Bacillus sublitis and Bacillus megaterium, exhibited the most effective inhibition against the pathogens of sheath blight and bakanae disease of rice. A few isolates from Bacillus pumilus and Bacillus megaterium showed weak virulent on rice together with some virulent isolates, risk should be considered when isolates from these species were screened for biocontrol agents.

Control Efficiency of Different Treatments on Rice Bakanae Disease

After different treatments, germination of rice seeds and growth of young seedlings were observed, and the optimal seed soaking agent was selected by comparing seedling growth and incidence of bakanae disease in the fidd. The results showed that self-made powder （800 times） could promote indoor seed germina- tion and seedling growth, had no obvious inhibitory effect on the growth of seedlings in the field, and could reduce the incidence of bakanae disease of rice seed- lings, so it was the optimal treatment for controlling rice bakanae disease.

Studies on Pathogenie Fusarium species of rice Bakanae disease and strains

We collected infection plants of rice bakanae desiease from 22 counties (cities) in Hubei Province in 1990-1992. Thirty five isolates of single spore were isolated from the plants. Fusarium species were identified from these isolates based on the method of Booth(1971) and other authors. Six kinds of medium wereused in the experiment. Color and growth rate ofcolonies as well as other characters were determinedfrom cultures grown on PSA. The results showedthat thirty one isolates were Fusarium moniliformevar. zhejiangensis, two isolates were Fusariumgramineum, one was Fusariurn oxysporum, and onewas Fusarium solani.

Current insights on rice(Oryza sativa L.)bakanae disease and exploration of its management strategies

Bakanae is an emerging rice disease caused by the seed-and soil-borne pathogen Fusarium fujikuroi.It is becoming a more serious threat to sustainable rice production throughout rice-growing regions.Bakanae disease infection is responsible for high yield losses ranging from 3%to 95%,and disease incidence varies based on the region and cultivars.Hence,understanding the nature of the pathogen,its pathogenicity,disease epidemiology,symptoms,host–pathogen interaction,and the role of secondary metabolites in the disease cycle will be helpful in the development of effective and sustainable management strategies.However,very few comprehensive studies have described the details of rice bakanae disease.Thus,in this review we summarize and discuss in detail the information available from 1898 to 2023 on various critical facets of bakanae disease,and provide perspectives on future research.

OsWRKY65 enhances immunity against fungal and bacterial pathogens in rice

Diverse bacterial and fungal pathogens attack plants,causing biotic stress and severe yield losses globally.These losses are expected to become more serious as climate change improves conditions for many pathogens.Therefore,identifying genes conferring broad-spectrum disease resistance and elucidating their underlying mechanisms provides important resources for plant breeding.WRKY transcription factors affect plant growth and stress responses.However,the functions of many WRKY proteins remain to be elucidated.Here,we demonstrated the role of rice(Oryza sativa)WRKY groupⅢtranscription factor OsWRKY65 in immunity.OsWRKY65 localized to the nucleus and acted as transcriptional repressor.Genetic and molecular functional analyses showed that OsWRKY65 increases resistance to the fungal pathogen Fusarium fujikuroi through downregulation of GA signaling and upregulation of JA signaling.Moreover,OsWRKY65 modulated the expression of the key genes that confer susceptibility or resistance to Xanthomonas oryzae pv.oryzae to enhance immunity against the pathogen.In particular,OsWRKY65directly bound to the promoter region of OsSWEET13 and repressed its expression.Taken together,our findings demonstrate that the OsWRKY65 enhances resistance to fungal and bacterial pathogens in rice.