TOBACCO WITCHES' BROOM. A PRELIMINARY REPORT

Abstract

While transmitting potato witches' broom to several varieties of potatoes, attempts were made to transmit this disease to Lycopersicum, Physalis, and Nicotiana. Witches' broom of potato and tomato have been described by Young and Morris.2 No symptoms appeared in the cultivated Physalis plants that were grafted to transmit witches' broom to them. Prominent symptoms of a distinct disease appeared in tobacco, which are described in the present paper. Normal stems of White Flowering tobacco plants were inarch-grafted on witches'-broom stems of Bliss Triumph, Burbank, and Six-Weeks potatoes, and on stems of Earliana and Bonny Best tomatoes having witches' broom. The various plants were kept in separate pots, and were often sprayed and fumigated to control insects. One of these tobacco plants grafted on an Earliana tomato with witches' broom showed several spindly little branches at the base of the tobacco stem about two months after grafting. Thirteen of these sprouts appeared within 83 days after grafting. Numerous slender axillary branches also developed, bearing greatly dwarfed leaves. The new leaves on the main stems were abnormally small. Many of them showed marginal flavescence,3 and most of them were entirely flavescent. This tobacco plant soon bloomed profusely, but the flowers were only half as long and thick as normal tobacco flowers of this variety (P1. XXI, fig. D). Later, rosettes of little leaves only I to 2 cm. long appeared on the stems. Many leaves turned white, with green veins and necrotic brown spots. This group of symptoms clearly distinguished this plant from 50 normal White Flowering tobacco plants that were successively observed during three years. The marginal flavescence of the leaves, and the abnormally numerous, spindling, axillary and basal branches were clear symptoms of a distinct disease.