SINGLE AND COMBINED EFFECTS OF THREE FUSARIUM SPECIES ASSOCIATED WITH RICE SEEDS ON THE SEVERITY OF BAKANAE DISEASE OF RICE

摘要

Fusarium spp. associated with susceptible rice variety Pusa Basmati 1121 were isolated. Based on translation elongation factor 1 alpha (TEF-1 alpha) Fusarium spp. were identified as F. fujikuroi, F. proliferatum, F. verticillioides (F. moniliforme), F. sacchari, F. pseudonygamai, F. thapsinum and F. andiyazi. Pathogenicity test conducted on susceptible variety Pusa Basmati 1121 confirmed that only F. fujikuroi, F. proliferatum and F. verticillioides produced bakanae disease as elongation, rotting or both types of symptoms. Gibberellic acid was exclusively extracted from the isolates of F. fujikuroi and it ranged from 450 mu g/g to 4361 mu g/g of mycelium. Gibberellic acid content was positively correlated (r = 0.79) with elongation symptom of the disease. Fusaric acid was present in all the species of Fusarium, ranging from 60 mu g/g to 2920 mu g/g of mycelium. However, significant correlation between fusaric acid content and disease severity could not be established. Co-inoculations of pathogens showed significant reduction in percent seed germination and increased disease severity compared to pathogen inoculated individually. Therefore, the present investigation will be helpful to understand the effect of different Fusarium spp. in bakanae disease etiology.