Establishment of an artificial inoculation system for the efficient induction of rice bakanae disease

Abstract

Bakanae disease, mainly caused by Fusarium fujikuroi, can lead to yield losses ranging from 10 to 20%. The lack of systematic researches on efficient propagation of pathogenic F. fujikuroi, artificial inoculation technology and the pathogenic conditions presents a critical technological gap that has severely hampered research on rice resistance to bakanae disease. This study first explored the sporulation conditions of F. fujikuroi in mung bean liquid medium, and determined that F. fujikuroi cultured in 40 ​g/L mung bean liquid medium for 2–6 days could efficiently produce pathogenic spores in large quantity. On this basis, we further establish an artificial inoculation system to induce bakanae disease. The main steps and parameters include: Soak rice seeds in a F. fujikuroi spore solution with a concentration of 1 ​× ​10⁶ conidia/mL for 2 days; let imbibed seeds germinate, and choose germinating seeds with buds of a grain length and cultivate them on half strength MS medium (1/2 MS, pH 5.8–6.8) for about a week. The characteristic bakanae symptoms of excessively elongated seedlings could thus be induced. Furthermore, we found that the bakanae disease symptoms became more profound when a small amount of PDA (0.5%) was added to 1/2 MS medium. Hence our study established a technical system for the artificial induction of bakanae disease involving the use of mung bean medium for rapid propagation of F. fujikuroi spores, seed inoculation and cultivation of seedlings in 1/2 MS medium added with 0.5% PDA. This system will enable quick assessment of bakanae disease resistance and thus will be useful for rice breeding.