Viruses that induce breaking in color of flower petals in pansies and violas

Abstract does not appear. First page follows.

Introduction

Pansies (Viola tricolor var. hortensis) and violas, or tufted pansies (Viola cornutus) in California home gardens, nurseries, and seed farms frequently show a conspicuous breaking in the color of flower petals. The flowers, especially violas, are often dwarfed and malformed. Such plants are frequently stunted. An investigation was undertaken to determine the cause.

When the trouble was found to be due to two viruses—celery-calico and western-cucumber-mosaic—the method of transmission and control of the diseases were investigated. A study was made of the symptomatology on pansies and violas infected with these viruses and with common-cucumber-mosaic virus (which has not been reported in California). Experiments were also conducted with viruses known to cause breaking in flower petals of other ornamentals, to determine whether any of these would induce the disease in pansies and violas. This paper reports the results of these investigations.

A review of the literature indicates that three references to a mosaic disease in species of Viola in the United States have appeared. Martin3(1926) mentions a “yellows—undetermined mosaic type” on pansy (Viola tricolor) in Washington, D.C. (Edson and Woods (1936)) report a mosaic on Viola sp. in the state of Washington. (Perone (1939)) lists pansy among twenty-nine ornamental flowering plants affected with mosaic in New Jersey, and in a general description of symptoms reports “breaking of blossoms on these host plants.”

In England, (Smith (1935), (1936a), (1936b), (1937) reported breaking in violas and stated that inoculation experiments “seem to show that the virus causing this variegation is a strain of cucumber-mosaic virus (cucumber virus I).” (Moore (1933-1942)) reported a mosaic on several pansies and violas in Somerset in 1936.

In New Zealand, Chamberlain (1936) described foliage symptoms and breaking in pansy, viola, and violet.

In New South Wales, (Dunn (1941)), in notes contributed by the biological branch, recorded for the first time a “mosaic (virus) of pansy (Viola tricolor) in Sydney, Metropolitan area.”