Identification of rice seed infection routes of Fusarium fujikuroi inciting bakanae disease of rice

Bakanae disease caused by Gibberella fujikuroi, Sawada, Wollenworth (teleomorph) (anamorph: Fusarium fujikuroi Nirenberg), is emerging as a serious disease of rice in India. Histopathological study of plant tissue during infection can provide valuable insight for understanding the pathogenesis and the mechanism of resistance. The early infection process of F. fujikuroi in rice was observed at microscopic level using light microscopes and scanning electron microscope (SEM). In seed, the pathogen was observed in the husk, embryo and endosperm with maximum colonization in the husk region. Different infectious structures such as swollen tip hyphae, infectious hyphae, appressorium and infection cushion were observed in F. fujikuroi-rice interactions. The estimates of per cent (%) transmission of inoculum (seed-seed; seedlings-seed and florets-seed) revealed maximum transmission of F. fujikuroi through florets followed by seedlings and seed. The present study established that the infection of rice plants by F. fujikuroi can occur through three routes namely seed, seedlings (soil) and florets (air). The information generated in the present study will be valuable for providing an understanding on the pathogenesis and help to device effective strategies for management of bakanae disease of rice.