Blast Disease Occurred on Wild Rice, Zizania palustris L. Caused by Pyricularia sp.

Abstract

Many blast lesions appeared on the leaf blades, leaf sheath, and panicles of wild rice (Zizania palustris L.) cultivated in paddy field, Narugo-machi in Miyagi Prefecture (University Farm of Tohoku University) in summer in 1993. The conidia collected from lesions on leaf blades and panicles were identified as Pyricularia sp. under light microscope. However, the size of the conidia and colony characteristics of wild rice isolates differed from Pyricularia sp. obtained from leaf blast lesion on Manchurian wild rice, Zizania latifolia. The wild rice isolates from leaf blade and panicle were produced the same, rather greater blast lesions on wild rice by spray inoculation. Thus, it is clear that the Pyricularia sp. is responsible for this disease on wild rice. Pathogenicity test on the wild rice isolates to many gramineous plants showed the same results as those of isolates from rice plant grown around the wild rice paddy field. And also the pathogenicity of the isolates were same to 2 isolates of Pyricularia oryzae Cavara maintained on PSA medium in our laboratory. Furthermore, the HPLC profile of toxic substances released in culture filtrate of wild rice isolate was the same as the profile of isolates from rice plant almost. From these results, it is revealed that the blast disease of wild rice was caused by rice blast fungus Pyricularia oryzae Cavara which came from the neighboring rice paddy field. This might be the first report of blast disease on cultivated wild rice.