EFFECT OF SALT STRESS ON PROLINE METABOLISM IN CALLI OF LYCOPERSICON-ESCULENTUM, LYCOPERSICON PENNELLII, AND THEIR INTERSPECIFIC HYBRID

Amino acid pools and enzyme activities of NH3-assimilation (glutamine synthetase, glutamate synthase), proline biosynthesis (pyrroline-5-car boxylate reductase), proline catabolism (proline dehydrogenase, prolin e oxidase), and ornithine transamination (ornithine transaminase) were determined in control and salinized (140 mM NaCl) calli from tomato r oots. Three populations were used: the domestic salt-sensitive Lycoper sicon esculentum Mill. cv. P-73, the wild salt-tolerant Lycopersicon p ennellii (Correll) D'Arcy, accession PE-47, and their F-1 interspecifi c cross, for which the relative growth rate on salt media was intermed iate to those of the parents. Compared with control conditions, prolin e levels increased with NaCl treatments by twofold, threefold, and six fold in the wild species, the F-1 hybrid, and the domestic species, re spectively. This proline accumulation in the F-1 and the domestic popu lations was not modulated by changes in the enzyme activities of proli ne biosynthesis or catabolism. NaCl tolerance, amino acid (proline, al anine, arginine, asparagine) content, and velocity of enzymes responsi ble for proline biosynthesis and catabolism are dependent on explant s ources (cotyledon, root) from which the F-1 calli were derived. The co mparison of proline (PRO) responses in the different calli and populat ions indicated (i) various changes in anabolic or catabolic rates of P RO metabolism for a given range of PRO accumulation and (ii) the prese nce in the F-1 of both wild and sensitive parent characters in growth and PRO responses.