CANDIDATE GENE EXPRESSION PROFILING DURING CHILLING IN TWO DIFFERENTIALLY TOLERANT CULTIVARS OF TOMATO

Low temperature is a major factor limiting the productivity and geographical distribution of many plant species, including important agricultural crops. The capacity to adapt to a cold environment is significantly different among species, and dividing them in acclimating and notacclimating ones. Many plants of tropical or subtropical origin, such as tomato, maize, soybean, and rice, are severely injured or even killed by exposure to low, nonfreezing temperatures. Most tomato cultivars are sensitive to chilling temperatures during all stages of plant development. Genetic variation for chilling tolerance exists between cultivated Solanum lycopersicum and its related wild species, but intra-specific variation has not been thoroughly investigated and fully exploited so far to improve such tolerance. The general objective of the present study was to give an insight into the molecular processes that underlie chilling tolerance in the chilling-sensitive species S . lycopersicum. Consequently, specific aims have been the selection of two tomato cultivars contrasting for their response to chilling exposure by means of a phenotypic characterization of a large germplasm collection. After the phenotypic screen and the choice of the two contrasting lines, a set of functional candidate genes belonging to gene families regulated by cold in plants have been chosen, and evaluated for cold-modulated expression by RT-PCR in the two cultivars. We report here results of genetic variation in the UniMORE germplasm collection for chilling tolerance (stress treatment at 1°C for 24h) together with the selection of Albenga (tolerant) and San Marzano (susceptible) cultivars. Then, twenty candidate genes induced by chilling and/or with putative roles in abiotic stress-response pathways have been then identified, in this first survey comprising both transcription factors and effector genes. Gene expression profiling was conducted by exposing plants to +1°C at a total of six time points. The study shows a first insight into cold modulated expression profiling of tomato cultivars contrasting for chilling tolerance.