Weeds experimentally infected with beet-mosaic virus

Abstract

does not appear. First page follows. Introduction It is important to know what plants growing in the cultivated areas and on the uncultivated plains and foothills are reservoirs of the beet-mosaic virus. After the pasture vegetation becomes dry on the plains and foothills, enormous flights of aphid vectors fly into the cultivated areas, and are often abundant on favorable weeds, varieties of beets, and other economic plants. Unpublished data indicate that the host range of the virus among economic plants is limited to plants belonging to the families of Azioaceae, Chenopodiaceae, and Papaveraceae. This paper deals with the weed host range of the beet-mosaic virus. A study was made of the sequence of symptoms of experimentally infected weeds so that naturally infected plants could be recognized in the field. Some reports on weeds susceptible to the virus have been published; these are discussed in connection with our results (pp. 570-571.) Methods Weeds grown from seeds were experimentally infected with the virus by mechanical inoculation using the carborundum method described by (Rawlins and Tompkins (1936)).4 The virus was recovered from each species of weed and transferred to sugar beets by the same method. Weed Host Range and Symptomatology Six species of weeds in three genera of the family Chenopodiaceae were experimentally infected by mechanical inoculation with the virus extract from mosaic-infected beets. Systemic infection occurred in all of the weeds from which the virus was recovered. The symptoms on the weeds experimentally infected with the virus are as follows. Bractscale. The symptoms on bractscale, Atriplex bracieosa, are cessation of growth and a bending and curling of the apical shoot (plate 1, B) on infected plants. The young leaves are dwarfed, cupped outward, occasionally twisted along the midrib (plate 1, C) sometimes asymmetrical, mottled with small chlorotic spots; later the leaves become necrotic. Necrosis of the young leaves and death of the apical shoot occur within 3 weeks after inoculation. Red Orache, or Redscale. The symptoms on red orache, Atriplex rosea, develop in essentially the same manner as those described on bractscale. All of the infected plants died within 3 weeks after inoculation.