Effect of growth regulators on Direct Organogenesis and rooting in Cotyledonary Explant of Lettuce (Lactuca sativa L. ̒TN96-39̓) landrace

An efficient in vitro regeneration protocol has been developed for lettuce TN96-39 which is one of the most important Iranian lettuce landrace genotypes. The goal of the present study was to describe an in vitro regeneration protocol, where different factors were optimized for maximum multiplication and propagation of TN96-39. Various factors including the age of the explant and plant growth regulators were analyzed. The results showed that, 3 day-old seedling explants were found to be the most responsive to the treatments. A maximum shoot number of (20.51 shoots/explants) were produced from 3 day-old seedling explants, with an average shoot length of (5.25 cm) in (87.00 %) cultures after 6 weeks of incubation on Murashige and Skoog medium supplemented with benzyl adenine (BA) (0.5 mg/l) + naphthalene acetic acid (NAA) (0.05 mg/l). The highest rooting frequency (97.0 %) with maximum of (7.53 roots/shoot) having an average root length of (4.76 cm) was obtained on half-strength MS medium with (0.1 mg/l NAA) and solidified with (0.7%) plant agar. The plantlets were acclimatized in sterile soilrite under controlled conditions, hardened and successfully transferred to soil in natural conditions with 90% survival rate.