First report of Fusarium oxysporum causing damping-off of tree bean (Parkia timoriana) seedlings in Northeastern India

Abstract

Tree bean (Parkia timoriana), is an important multipurpose leguminous tropical deciduous tree species widely grown in the Northeastern states of India. The occurrence of the high incidence of damping-off (86.19%) disease was observed in tree bean nursery grown in Umiam, Meghalaya, a state in Northeastern India. Therefore, a systematic study was undertaken to record the symptoms and characterize the morphological features, the taxonomy of pathogen causing damping-off disease of P. timoriana and confirm it by pathogenicity assay. The infected seeds exhibited typical symptoms of covering with whitish mycelium and cotyledons were completely rotten in later stages of infection and emitted foul odour. Infected seedlings exhibited the symptoms of root rot followed by wilting, dried stem, and complete mortality of the seedlings. The pathogen isolated from the rotten seeds and wilted seedlings consistently showed the association of Fusarium oxysporum and its identity was confirmed based on morphological characteristics and sequences of ITS-rDNA and TEF genomic regions. Five representative isolates (TBSR 1 to 5) exhibited high similarity (>98%) to the known authentic gene sequence of F. oxysporum. The pathogenicity test produced similar to natural symptoms of wilt at 30 days after inoculation, confirming the etiological association of Fusarium oxysporum. To the best of our knowledge, this is the first to report on F. oxysporum causing damping-off disease of P. timoriana in India and worldwide.