Effect of genotype and explant type in regeneration frequency of tomato in vitro.

In order to develop transgenic tomato plants resistant to CMV via Agrobacterium mediated transformation, the regeneration frequency of hypocotyl, cotyledon and leaf explants of different tomato (Lycopersicum esculentum) cultivars was investigated in in vitro cultures. Leaf explants from greenhouse plants as well as cotyledon and hypocotyl explants from seedlings germinated in vitro were cultured on MS medium supplemented with various concentrations of plant growth regulators under controlled environmental conditions. Benzyladenin or Zeatin at concentrations ranging from 0.1 to 10 mg/l induced multiple shoot regeneration. The order of shoot regeneration was from hypocotyls to cotyledons to leaves. Genotypic differences were observed in the morphogenetic capacity of cultured explants. Tomato cv. San Marzano nano, San Marzano and Principe Borghese regenerated shoots most readily of an average number 7.95, 7.05 and 5.35 shoots per explant, respectively. The rate of explants expressing shoot forming capacity for the same cultivars was 95-100%. Tomato cv. ACE 55 VF and Pakmor regenerated shoots more slowly of an average number 2.60 and 2.75 shoots per explant, respectively. After four weeks of culture only 30% of the explants formed shoots, but after 8 weeks 80% of the explants differentiated shoots.