Endophytic Xylaria sp. enhances tolerance in rice to bacterial leaf blight and promotes growth

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive bacterial diseases of rice world wide. In the present study, five fungal endophytes isolated from rice leaves were tested for their antagonistic potential against Xoo. The endophyte isolate viz., KTD-2 inhibited the bacterial pathogen. The antagonism was visualized as overgrowth of the endophyte on the pathogen followed by degradation of its yellow pigmentation. The isolate could also successfully colonize the roots of rice plants within two weeks of inoculation. Phylogenetic analysis based on ITS and LSU sequences revealed that the endophyte belonged to the Xylariaceae family. Further characterization clustered the endophyte to the Xylaria genus with 95.35 and 94.04 per cent sequence similarity to Xylaria sicula f. major when sequenced with the btub and rpb-2 genes respectively. This is the first report of endophytic Xylaria sp. isolated from rice antagonistic to Xoo. Endophyte application as seed treatment and foliar application significantly reduced disease severity to 28.89% compared to 79.26% in the control at 90 days after transplanting (DAT). Seed treatment significantly enhanced seed germination to 94.31 per cent compared to 88.46 per cent in untreated control. The in vitro study revealed that the germination percentage, seedling length as well as the seedling vigour index were the highest in endophyte treated seedlings compared to untreated seeds. This strongly suggests that the identified endophyte, KTD-2 is a potential candidate for biological control for the management of BLB along with plant growth promoting activities.