Riboflavin (Vitamin B2) mediated defence induction against bacterial leaf blight: probing through chlorophyll a fluorescence induction O–J–I–P transients

Bacterial leaf blight (BLB) is a serious threat for rice (Oryza sativa L.) cultivation caused by the bacterial pathogen Xanthomonas oryzae pv. oryzae. The pathogen mainly damages the leaf chlorophyllous tissue, resulting in poor photosynthesis and causing up to 50% reductions in grain yield. In the present work, we have compared the structural and functional ability of the chloroplast of three varieties of rice with different degrees of susceptibility (TN1, highly susceptible; IR-20, moderately resistant; DV-85, resistant to BLB) treated with riboflavin (1 and 2 mM) and infected with BLB, with chlorophyll fluorescence as a tool. As indicated by the chlorophyll fluorescence technique, the disease progress curve and yield data, riboflavin acted as an effective vitamin for inducing resistance against BLB. Plants treated with riboflavin showed improved PSII activity, more chlorophyll content and higher yield than the diseased plants.