Studies On Aseptic Seed Germination And Regeneration In Loquat

Loquat has important research values,but there is still no stable regeneration system.In this study,the germination of different cultivars of loquat seeds,the factors of seed germination and the effects of storage on seed germination were studied and the disinfection methods of loquat seeds were optimized.Using aseptic seedlings,regeneration of loquat was studied by direct and indirect adventitious shoot regeneration pathways,through induction of adventitious buds from explants for the direct pathway,and firstly induction of callus from explants and then differentiation of buds from callus for the indirect way.The main results were shown below:1.Through comparison of seed germination of 13 loquat cultivars,the germination rate and seedling height of white-fleshed loquat seeds were generally higher than that of red-fleshed loquat seeds.Through determination of the content of endogenous ABA and IAA,the results showed that the content of ABA was negatively correlated with the germination rate while the content of IAA was not significantly correlated with the germination rate at 80 days after sowing.Besides,omitting the ethanol promoted seed germination.The effects of promotion on'Dahongpao' seed germination were higher than that on 'Yingtiaobaisha' seed germination.2.The maturity of fruits had little effect on the germination of loquat seeds.However,there were differences between cultivars.For example,the seeds of fully mature 'Oobusa' fruits have a higher germination rate(the germination rate is 73.33%and that is 2.5 times of germination rate of seeds from color-changed period fruits).Besides,the storage methods had little effect on the seed germination rate(fruit storage and seed storage),which was mainly affected by storage days.Specifically,the seed germination rate of the two storage methods was not significantly different and was significantly decreased after stored for 20 d or more.For example,the germination capacity of loquat seeds was lost after stored for 40 d.Moreover,the characteristics of stored loquat seeds were quite different between cultivars.The results showed that 4? and 15? had little effect on the germination of'Zaozhongliuhao' seeds,but 25? significantly inhibited seed germination.And different temperatures had little adverse effect on the germination of 'Taipingbai'seeds.Generally,15? can be used as the preferred test temperature for loquat seeds storage.Through studies of seed storage and advance harvesting,the supplied period of loquat seeds can be prolonged.3.Different explants(leaves,cotyledons and stems),different cultivars and different seedling ages of adventitious buds were all difficult to regenerate from cotyledons directly.Callus were easier to induce from leaves,but the adventitious buds were still very difficult to be induced from callus.Moreover,whether explants were easy to be regenerated and the optimal kinds and concentrations of plant hormones were varied with cultivars.White-fleshed loquat 'Yingtiaobaisha' and'Ninghaibai' were earlier and most likely to form callus,and red-fleshed loquat'Dawuxing' and 'Dahongpao' callus induction were relatively difficult.The best medium for 'Yingtiaobaisha' and 'Dahongpao' was MS6(MS + 1.0 mg/L 6-BA + 0.8 mg/L 2,4-D + 0.4 mg/L NAA).The optimum medium for 'Ninghaibai' was MS4(MS+ 0.5 mg/L 6-BA + 1.0 mg/L 2,4-D).The optimum medium for 'Dawuxing' was MS5(MS + 0.5 mg/L 6-BA + 2.0 mg/L 2,4-D).