The System Of Embryo Culture And Shoot Regeneration From Cotyledons Of Pear Cultivars

The stable efficient plant regeneration system is the prerequisite to success for transformation. In this study, the embryo of different periods of 'Jinhua' (Pyrus bretschneideri), 'Jinshui' (P. pyrifolia) and 'Cangxi' (P. pyrifolia) were used as explants. By means of the orthogonal experiment design, analysis of variance and multiple comparisons, the factors inculding the times of getting material, dark periods, plant growth regulators, AgNO3 concentrations were analyzed and the system of in vitro culture and shoot regeneration from cotyledons of pear cultivars was established. The results were as follows:1. The best time was 60 days after post-pollinated fruits from pear cultivar considering contamination, browning in vitro and death rate.2. In comparison with regenration rate and shoot per cotyledon, the optimal initiation medium for shoot regeneration of each cultivar was respectively as follows:For 'Jinhua' and 'Cangxi' , shoot regenerated best on NN69 supplemented with 0.2mg/L NAA and 3.0mg/L BA with a regeneration rate of 83.41% and 70.74%. The highest regeneration frequency accounted for 76.60% when cultured 'Jinshui' on AS medium supplemented with 0.5mg/L NAA and 2.0mg/L BA.3. Auxin played an important role in the shoot regeneration from the cotyledons of pear. NAA was more effective than IBA and 2,4-D.4. Three weeks of dark trentment increased the shoot regeneration rate from 72.11%to 85.24%. However, with the extension of dark periods(28 days), the shoot regeneration rate decreased.5. 'Jinhua' shoot regeneration frenquency was enchanced on medium containing l-4mg/L AgNO3 , the best effection is 2mg/L AgNO3, the shoot regerenation from 72.11% to 85.25% ; while the addition of AgN03 8 mg/L help to stimulated 'Cangxi' shoot regeneration.6. Multiplication culture: for 'Jinhua' the best of propagation on MS supplemented with 2.0mg/L BA and 0.2mg/L IBA could reach 5.94; for 'Jinshui' the propagation multiply was 5.63 on MS supplemented with 1.0mg/L BA and 0.1mg/L IBA; for 'Cangxi' the best of propagation on MS supplemented with 2.0mg/L BA and 0.1mg/L IBA could reach 5.94.7. According to rooting rate, mean root number, mean root length, the optimal condition for three cultivars was respectively as follows:For 'Jinhua' , the best of rooting on 1/3MS supplemented with 0.5mg/L NAA , 2.0mg/L IBA and 0.5mg/L AC with rooting rate of 66.71%;For 'Jinshui' , shoots were placed in the medium of 1/2MS supplemented with 1 .0mg/L NAA , 2.0mg/L IBA and 0.5mg/L AC with rooting rate of 56.92%;For 'Cangxi' , microcuttings were inoculated in 1/4MS supplemented with 2.0mg/L IBA and 0.5mg/L AC with rooting rate of 63.16%.