Cumulative concentrations of tobacco mosaic virus in tobacco and tomato at different temperatures

Assays from inoculated leaves, tip leaves, and composite samples of all the leaves of tobacco and tomato systemically infected with TMV, as well as assays from roots and composite stem and leaf samples of tomato, revealed that, initially, virus concentration increased with an increase in air temperature from 16° to 28°. Subsequent assays from susceptible tobacco and tomato showed an orderly shift of virus concentrations among the different temperatures. In periodic tip leaf assays from any group of plants, there were alternating high and low virus concentrations which coincided directly with periods of severe and mild symptoms, respectively. In resistant tobacco, the highest virus concentrations were always found in plants grown at the highest temperatures where severe symptoms were produced.In soil temperature studies with tobacco, virus concentration initially increased with an increase in soil temperature from 16° to 28°. Later assays revealed a definite reversal of virus concentration order in regard to temperature in susceptible tobacco in that highest concentrations were found in plants grown at 16°. No such reversal occurred in resistant tobacco. Studies on the interaction of air and soil temperatures indicated that soil temperature was less important in determining initial virus concentration in the inoculated leaves and composite samples of all the leaves than air temperature.Data of virus concentration and host growth plotted in cumulative curves showed a definite relationship between rate of host growth and virus concentration. After maximum virus concentrations were reached, as host growth increased, virus concentration decreased.