Spinach yellow dwarf

Abstract does not appear. First page follows.

Introduction

Five virus diseases of spinach (Spinacia oleracea L.) have thus far been reported to occur under natural conditions in the United States-namely, spinach blight (McClintock and Smith, 1918)4, which is identical with common cucumber mosaic (Hoggan, 1933); aster yellows (Kunkel, 1926); (Severin, 1934); (Severin and Frazier, 1945); sugar-beet curly top (Severin and Henderson, 1928); (Scott, 1935); (Adams, 1936); beet mosaic (Jones, 1931); (Hoggan, 1933); (Smith, 1934); and spotted wilt (Gardner, Tompkins, and Thomas, 1937).

This paper deals with still another naturally occurring virus disease of spinach-bspinach yellow dwarf. The aspects covered include symptoms and host range of the disease, the properties and aphid vector of the virus, transmission of the virus by single aphids, a comparison of the transmission of the virus by one species of aphid with mechanical inoculation, and retention of the virus by aphids.

Materials and Methods

Source of Virus. The source of the spinach-yellow-dwarf virus was naturally infected spinach plants obtained from the truck-crop fields near San Pablo. The virus was retained through repeated mechanical inoculations and aphid transmission to spinach.

Spinach Extract. Juice from diseased spinach plants was obtained by grinding the plants to a-pulp in a sterilized food chopper or mortar. The pulp was then placed between two layers of cheesecloth and the sap expressed by hand into a sterile glass dish.

Mechanical Inoculation. The method of mechanical inoculation used is that described by (Rawlins and Tompkins (1936)). After inoculation, the inoculum and the carborundum were washed from the leaves with water. The virus extract from each preparation was inoculated into 5 healthy spinach plants.

Variety of Spinach. Long Standing Bloomsdale spinach was used in studies of properties and aphid transmission of the virus and as a source of virus in host-range studies. This variety grows rapidly and remains in good condition a long time without bolting to seed.

Noninfective Aphids. Noninfective green peach aphids were obtained from populations reared on healthy sugar beets maintained in the greenhouse.

Methods of Transferring Aphids. High populations of aphids were transferred by cutting off leaves which bore large numbers of aphids, then placing the leaves on the inner or youngest leaves of another plant.