Morphology and Distribution of Deformed Panicles in Downy Mildew Diseased Rice

Abstract

Deformed panicles and spikelets of downy mildew (Sclerophthora macrospora (Sacc.) Thirum., Shaw et Naras.) diseased rice were investigated to elucidate the morphology and distribution of deformed panicles in a paddy field in Akita Prefecture, which was flooded on July 6 (28 days before heading), 2012. The deformed panicles were classified into elongated type, shortened type, and elongated-shortened type. The panicles in the elongated type were long with a few spikelets, long glumes, and long awns. The panicles in the shortened type had short culms, short panicles, many spikelets and short glumes. In the elongated-shortened type, the upper part of the panicles was of the elongated type, and the basal part was of the shortened type with a high percentage of proliferation. The percentage of proliferation, awned spikelets, and long glumes was higher in the first and secondary spikelets, while the percentage of short glumes was higher in the tertiary spikelets. The percentage of hills with deformed panicles was 66%, while the percentage of deformed panicles was 7.8%. The deformed panicles were observed more in the poorly drained area around the inlets. The percentage of deformed spikelets of the deformed panicles was more than 80%. The estimated yield loss was 6%.