Protoplast and leaf explant culture of Lycopersicon cheesmanii and salt tolerance of protoplast-derived calli

In vitro manipulation of Lycopersicon cheesmanii was attempted in order to evaluate its potential to improve salt tolerance of L. esculentum following somatic hybridisation of these two species. The main study concerned three populations of the typicum form (LCS) used for tissue culture and protopla st studies. The minor halophytic form (LCT) was used only for protoplast ex periments. Mother plants were sown and propagated in vitro. Shoots (2-7) we re obtained from explants (leaflets, petioles, cotyledons), through calli, when 3-4 mg l(-1) BA, kinetin or 2iP were used in association with auxin. I AA (0.2 and 1 mg l(-1)) was the most efficient, while 2,4-D or NAA were som etimes inhibitory according to genotype and explant. Leaf protoplasts (2-5 x 10(7)/g of fresh weight) were obtained from LCS and LCT. For LCT, protopl ast division declined after five subcultures of the plantlets that had been established from seeds. Protoplast-derived calli were obtained from all po pulations (maximum PE 30% for LCS). However, they failed to regenerate shoo ts. Protoplast-derived calli involved in salt tolerance tests showed that L CS17 line was the most tolerant.