RESPONSES OF DIFFERENT TOMATO VARIETIES TO DISEASE STRESS UNDER DIFFERENT CONDITIONS OF GRAVITY

Résumé

A study was carried out to evaluate the responses of different tomato varieties to fungal disease stress under different conditions of gravity, in Lafia, Nasarawa State Nigeria. Seeds of three local tomato varieties namely; UTC, Teema and Dan Syria were plated on plant agar inoculated with culture filtrates of Sclerotinia sclerotiorum and Pythium ultimum, and rotated on a clinostat at a speed of 20 revolutions per minute (rpm) for 96 hours in a dark growth chamber. Seedlings of Dan Syria subjected to the condition of normal gravity had the highest Frequency of germination (79.61%), seedling height (4.01mm) and stem girth (0.19mm). Teema had the
highest width of vascular bundles (1.18mm) under normal gravity condition. Under conditions of microgravity, the highest number of trichomes (15.38), plant height (3.25mm), width of epidermis (0.19mm), and frequency of germination (66.63%), were observed in the UTC variety. The least frequency of germination (27.75%) and seedling height (1.06mm) was observed in Dan Syria under the condition of microgravity. Trichomes were absent in seedlings of Dan Syria under normal gravity. Seedlings of Dan Syria, UTC, and Teema subjected to disease stress revealed absence of stomata on exposure to microgravity conditions. Differences in effect of gravity conditions on morphological and anatomical features of the seedlings were significant (P≤0.05). The UTC tomato variety showed higher disease tolerance under microgravity stress, and could be considered for genetic studies aimed at selection of stress tolerance genes in the tomato variety, for enhanced yield and productivity