Physiological and biochemical alterations imposed by Fusarium fujikuroi infection in aromatic and non-aromatic rice cultivars

Bakanae is the major fungal disease of rice posing threat to rice production all over the world. In order to understand the physiological and biochemical basis of resistance, the disease free and Fusarium fujikuroi infected seedlings of two aromatic (PUSA 1121 and PUSA 1509) and two non-aromatic (PR 121 and PR 126) rice cultivars were evaluated. The seeds of rice cultivars were inoculated with the virulent isolate of F. fujikuroi. Percent disease incidence, percent field emergence, seedling length and biochemical traits of 25 days old seedlings raised from healthy (disease free) and pathogen inoculated seeds in the nursery were compared. The experimental design was RBD and data was analysed using tukey’s HSD test. The infection led to a significant decline in the chlorophyll content in the infected seedlings of the aromatic cultivars, whereas non-significant variation between healthy and infected seedling of non-aromatic rice cultivars was observed. Seed inoculation with the fungus resulted in significant increase in length of the infected seedlings in aromatic rice cultivars as compared to non-aromatic indicating the resistance response to the production of Gibberellic acid in non-aromatic rice cultivars. The endogenous GA enhanced significantly postinfection in the aromatic PUSA 1121 and PUSA 1509 seedlings. Post pathogenesis, the infected seedlings of aromatic cultivars retained lower level of total phenols. The depletion of phenols post infection in infected seedlings of aromatic cultivars may be due sugar depletion. Our results show that the higher total antioxidant and enzymatic activity in aromatic rice cultivars post infection could be a useful biochemical marker for screening the tolerance potential of rice cultivars against bakanae disease.