The System Of In Vitro Culture And Shoot Regeneration From Cotyledon Of Balsam Pear

The stable efficient plant regeneration system is the prerequisite to success for transformation. In this study, the cotyledon of different age of 'Cuifei' and 'Cuixiu' were cultured in vitro. The factors including age and site of cotyledon, genotypes, basic media, plant growth regulators, dark period, AgNO₃ concentrations were analyzed and the system of in vitro culture and shoot regeneration from cotyledons of balsam pear was established. The results were as follows:(1) Age of cotyledon: Different age of cotyledon has different effect on balsam pear shoot regeneration. In this experiment, we found the age of 9 day was the best period for shoot regeneration from cotyledon of 'Cuifei' and 'Cuixiu'.(2) Site of cotyledon: Different site of cotyledon has different effect on shoot regeneration. In this experiment, we found the site near to hypocotyl was the best site for shoot regeneration from cotyledon of 'Cuifei' and 'Cuixiu'.(3) In Comparison with regeneration rate and shoot per cotyledon, the optimal initiation medium for shoot regeneration of each cultivar was respectively as follows:For 'Cuifei' and 'Cuixiu' , shoot regenerated best on MS supplemented with 0.2mg/L NAAand 1.0mg/L BA with a regeneration rate of 54.21% and 19.45% respectively.(4) CTK played an important role in the shoot regeneration from the cotyledon of balsam pear, BA was more effective than KT in inducing shoot regeneration from cotyledon of balsam pear.(5) Auxin played an important role in the shoot regeneration from the cotyledons of balsam pear. For 'Cuifei' NAA was more effective than IAA, IBA and 2,4-D; For 'Cuixiu' NAAand IAA were the same effective as IAA and 2,4-D.(6) One week of dark treatment increased the shoot regeneration rate of 'Cuifei' and 'Cuixiu' from 51.98% and 18.90% to 77.44% and 35.31%. However, with the extension of dark periods, the shoot regeneration rate decreased.(7) On the best combination of plant growth regulators for shoot regeneration, the addition of AgNO3 varied from Onig/L to Snig/L in the medium could not help to stimulate show! regeneration, only growing a few roots.(8) Multiplication culture: for 'Cuifei' the best of propagation rate on MS supplemented with 0.5mg/L BA and 0.1 mg/L NAA could reach 5.40; for 'Cuixiu' the propagation rate was 5.06 on MS supplemented with 0.75mg/L BA and 0.1 mg/L NAA.(9) According to rooting rate, the optimal condition for two cultivars was respectively as follows:For 'Cuifei' the best rooting medium was MS supplemented with 0.25mg/L NAA and the rooting ratewas 99.15%For 'Cuixiu' the best rooting medium was MS supplemented with 0.25mg/L NAA and the rooting rate was 93.51%.