Spray Application of Nonpathogenic Fusaria onto Rice Flowers Controls Bakanae Disease (Caused by Fusarium fujikuroi) in the Next Plant Generation

• Published in: Applied and environmental microbiology Vol. 87; no. 2; pp. 1 - 14
• Main Authors: Saito, Hiroki, Sasaki, Mai, Nonaka, Yoko, Tanaka, Jun, Tokunaga, Tomomi, Kato, Akihiro, Thuy, Tran Thi Thu, Vang, Le Van, Tuong, Le Minh, Kanematsu, Seiji, Suzuki, Tomotaka, Kurauchi, Kenichi, Fujita, Naoko, Teraoka, Tohru, Komatsu, Ken, Arie, Tsutomu
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 04-01-2021
• Subjects: Biological control; Blight; Control methods; Disease control; Disinfection; Elongation; Etiolation; Farms; Flowers; Flowers - microbiology; Fluorescence; Fungi; Fusarium; Fusarium fujikuroi; Oryza - microbiology; Pest Control, Biological; Plant diseases; Plant Diseases - prevention & control; Plant Microbiology; Plants (botany); Rice; Sanitation; Seedlings; Seeds; Signs and symptoms; Spores, Fungal; Spotlight; Spraying; bakanae disease; Fusarium fujikuroi; flower spraying; biocontrol; seed-borne; nonpathogenic Fusarium commune
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.01959-20

Bakanae disease, caused by
, is an economically important seed-borne disease of rice.
is horizontally transmitted to rice flowers and vertically transmitted to the next generation via seeds. The fungus induces typical symptoms such as abnormal tissue elongation and etiolation. Sanitation of seed farms and seed disinfection are the only effective means to control bakanae disease at present; however, the efficacy of these methods is often insufficient. Therefore, alternative and innovative control methods are necessary. We developed a novel method for applying nonpathogenic fusaria as biocontrol agents by spraying spore suspensions onto rice flowers to reduce the incidence of seed-borne bakanae. We visualized the interaction between
W5, a nonpathogenic fusarium, and
using transformants expressing two different fluorescent proteins on/in rice plants. W5 inhibited hyphal extension of
on/in rice flowers and seedlings, possibly by competing with the pathogen, and survived on/in rice seeds for at least 6 months.
We demonstrated that a spray treatment of rice flowers with the spores of nonpathogenic fusaria mimicked the disease cycle of the seed-borne bakanae pathogen
and effectively suppressed the disease. Spray treatment of nonpathogenic fusaria reduced the degree of pathogen invasion of rice flowers and vertical transmission of the pathogen to the next plant generation via seeds, thereby controlling the bakanae disease. The most promising isolate,
W5, colonized seeds and seedlings via treated flowers and successfully inhibited pathogen invasion, suggesting that competition with the pathogen was the mode of action. Seed-borne diseases are often controlled by seed treatment with chemical fungicides. Establishing an alternative method is a pressing issue from the perspectives of limiting fungicide resistance and increasing food security. This work provides a potential solution to these issues using a novel application technique to treat rice flowers with biocontrol agents.