SOME EFFECTS OF NITROGEN SUPPLY ON THE INFECTION OF TOMATO PLANTS WITH TOMATO SPOTTED WILT VIRUS

The susceptibility of tomato plants to systemic infection by tomato spotted wilt virus was increased by increasing nitrogen supply to levels above that optimal for growth. The virus content, estimated by local-lesions counts, was also raised by increasing nitrogen. The period between inoculation and the appearance of systemic symptoms was decreased by increasing nitrogen to a point slightly greater than the optimal level for growth, but increased by additional applications.
Infected plants receiving more nitrate or ammonium compounds than were needed for optimal growth showed abnormal leaf symptoms and no bronzing. N, P and Mg analyses showed that these symptoms were related primarily to nitrogen content. Such leaves contained more virus than bronzed leaves.     

TOMATO TRICHOMES AND MUTATIONS AFFECTING THEIR DEVELOPMENT

A new trichome type for the genus Lycopersicon is described in L. esculentum Mill. It is a short (0.03–0.08 mm), pendant, glandular hair with a club-shaped head consisting of 8–12 cells. Two previously described “hairless” mutations were examined microscopically. One, hl, does not affect the frequency of hairs nor the number of cells per hair, but causes abnormal enlargement of the stalk cells of all hair types, and thus produces shortened, extremely bent and twisted hairs. Observations on the time of action of this gene indicate that in trichome development two to four cell divisions occur prior to any appreciable cell enlargement. The second mutation, h, affects only the large type of trichome. This mutation effects a developmental shift from trichome to stomatal apparatus at the apex of the multicellular base normally supporting the large trichomes.     

RECOVERY FROM CURLY-TOP DISEASE IN TOMATO SEEDLINGS

Plants of commercial varieties of tomato cease to grow normally and usually die, when infected by curly-top virus by means of the beet leafhopper. Only rarely does an infected plant resume and maintain growth, i.e., recover. However, when tomato seedlings were infected with curly-top virus by means of the beet leafhopper, some plants of six of seven commercial varieties recovered. The best recovery of plants in a single trial was 20% in ‘Penn Orange’ infected with the Paso Robles strain of virus. The per cent and degree of recovery of infected seedlings were influenced by the variety of tomato, severity of the virus strain on the seedlings, and probably by factors affecting rate of development of both plant and virus.