Browning Control And Callus Induction In In Vitro Culture Of Petioles And Veins In Loquat

In this study, leaves harvested from 10 year-old mother plants of loquat (Eriobotrya japonica L.) were used as experimental materials, the petioles and veins as explants, the browning control in in vitro culture, callus induction and callus sub-culture were studied including the effects of explants surface sterilization methods, leaf developmental stage, positions of petioles and veins, strength of MS medium, PVP concentrations, cold treatment at 4℃, growth regulators, dark culture, low temperature culture, transfer of cultures, callus induction and sub-culture. The results were as follows.1.The surface sterilization of explants were achieved with 75% alcohol for 10s, then 0.1% HgCl2 for 8 min, resulting in lowest contamination rate and browning rate (14.44% and 8.89%, respectively), at the same time high survival rate and callus induction rate (all 76.67%).2.Leaf developmental stage and positions of petioles and veins:the moderately mature (about 10 days) leaves and petioles were the ideal materials, and survival rate and callus induction rate were higher (55.56% and 53.33%, respectively), the callus structure was tight, light green, and with the best physical condition.3.The best treatment for browning control was in 1/8 MS medium with PVP 1.5mg/L and no 4℃ treatment, resulting in a lowest browning rate(11.11%) and highest survival rate (80.00%) and callus induction rate (77.78%).4.The best formula for loquat leaf petioles and veins callus induction was MS+ 6-BA 1.0mg/L+2,4-D 1.5 mg/L+NAA 0.4 mg/L, in which browning rate was 17.78% and survival rate and callus induction rate were all 72.22%.5.The best culture conditions and culture transfer times were culture temperature at 20 ℃, dark culture for two weeks, explants transfer per 5 days, resulting in the lowest browning rate, highest survival rate and callus induction rate (15.74%,75.82% and 69.93%, respectively).6.The best formula for callus sub-culture was MS(1/2N)+TDZ 1.0 mg/L+NAA 0.3mg/L+AgNO30.2mg/L, in which calluses were granular, partial surface protrusions, tight, green, some white particles on the surface and no browning.