Abstract
Rice ragged stunt causes symptoms distinct from rice grassy stunt: the symptoms are stunting of plants, twisted, ragged, and shortened leaves, branching of tillers, panicle emptiness, and galls along the veins. Virus-like particles of 55-60nm in diameter occurred in dip preparations from the leaf and gall tissues of ragged stunt-diseased rice plants stained with phosphotungstate. Similar particles were found in extracts obtained from infectious vectors Nilaparvata lugens Stal. When the tissues were fixed with glutaraldehyde before dipping, particles had “spikes” around their periphery and 1-6 filaments were extended from the particles. Galls resulted from hyperplasia of phloem tissues and gall cells contained amorphous inclusions visible with the light microscope. Virus-like particles were embedded in viroplasm-like inclusions or were scattered in the cytoplasm of phloem and gall cells. Particles were about 65nm in diameter and had electron dense cores of about 45nm surrounded with less electron dense shells. Thirty to ninety percent of insect vecotrs in infectious colonies contained virus-like particles and about 1/2 to 1/3 of these insects were transmitters. Thin sections of insect transmitters showed that virus-like particles were embedded in viroplasm-like inclusions in the cells of the salivary glands, nerve tissues, muscles, fat bodies, and fore-gut. Particles were abundant and aggregated in crystalline arrangements in salivary glands and fat-body cells. Tubules with virus-like particles occurred in fat-body cells.
