TITLE:
Morpho-Physiological Traits Linked to High Temperature Stress Tolerance in Tomato (S. lycopersicum L.)
AUTHORS:
Muhammed Alsamir, Nabil M. Ahmad, Tariq Mahmood, Richard Trethowan
KEYWORDS:
Tomato Traits, High Temperature Stress, Hydroponic Media, Heat Stress Response
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.8 No.11,
October
19,
2017
ABSTRACT: The identification
of heat tolerance traits that express across environments is key to the successful
development of high temperature tolerant tomatoes. A replicated experiment of 145
tomato genotypes was established at two temperature regimes in two planting seasons
using hydroponics in a poly greenhouse to assess high temperature tolerance. Electrolyte
leakage, number of inflorescences, number of flowers and fruits, fresh
fruit weight and fresh and dry plant weight were measured and genotype and temperature
treatment differences were observed for all traits. Planting season impacted all
traits except electrolyte leakage and number of flowers. High temperature reduced
number of fruits by 88.8%, flower fruit set ratio by 77.2% and fresh fruit weight by 79.3%. In
contrast, traits little impacted by temperature included number of flowers per inflorescence
(1.3%) and plant dry weight (11.1%). The correlation between plant dry weight under
both high and optimal temperature was significant (R2 = 0.82). To assess
the effectiveness of plant dry weight and flower-fruit set ratio for selection under
heat stress two subsets of genotypes (A and B) comprising ten and six genotypes
respectively, were subsequently selected on the basis of their dry weight loss and
flower-fruit set ratio under high temperature. Organic metabolite analyses of set
A and B respectively, showed a significant change (%) in citric acid (77.4 and 15.4),
L-proline (117.8 and 40.2), aminobutyric acid (68.6 and 11.8), fructose (24.9 and
21.3), malic acid (50.3 and 42.7), myo-inositol (55.1 and 6.1),
pentaerythitol (54.1 and 39.0) and sucrose (34.7 and 25.8). The change (%) in all
metabolites was greater in heat tolerant genotypes with the exception of fructose and sucrose where sensitive genotypes produced
a higher variation. The change in sucrose in tolerant genotypes was variable
in subset A and more uniform in subset B. Flower-fruit set ratio was found as a
reliable trait for discriminating between heat tolerant and sensitive genotypes
and the sucrose levels in plant tissues provided confirmation of the heat stress
response.