Studies On The Embryo Rescue For Intraspecific And Interspecific Hybrids Of Sweet Cherry

European sweet cherry（Prunus avium L.）is known as big cherry,sweet cherry and is the plants of.the rose family plum genus cherry subgenus.Due to bright color,sweet and delicious,rich in microelement,high economic value,the fruit is known as‘the first branch of all fruit’.Although the fruit of sweet cherry has short development,early maturity,safe and healthy fruit,most of the cultivars have poor adaptability to the southern habitat,self-incompatibility and low germination rate.Intraspecific and interspecific hybridization and hybrid embryos rescue of sweet cherry and Chinese cherry are of great significance for overcoming self-incompatibility and embryo abortion of sweet cherry and enriching the resources of cherry in south China.The aim of this experiment is to select the best way to rescue hybrid embryos,improve the seedling rate of hybrid embryos and obtain hybrid seedlings.The hybridization and embryo rescue（before embryo abortion）was carried out with sweet cherry‘Jiangnanhong’‘Chaoyang-1’‘Changfeng-1’‘Van’as female,Chinese cherry‘Duanbing’‘Zijin’‘Chaozaohong’‘Gejiawu’‘Heizhenzhu’and sweet cherry‘04-8’‘04-11’‘Chaoyang-1’‘Van’‘Lapins’（a total of 10 cultivars）as male.By studying the effects of embryos age,genotypes,sterilization method of hybrid embryos,low temperature stratification,seed coat and types of culture medium on embryo rescue,the steps and methods suitable for hybrid embryos rescue were selected and a number of hybrid seedlings were successfully transplanted to the greenhouse.The experiment further accelerated the process of sweet cherry breeding and provided a certain basis for selecting new varieties of high quality sweet cherry in southern China.The results showed that:1.The fruit-setting rate of hybrid combinations was high 1 week after pollination,but decreased 4 weeks after pollination（stone stage）with hybrid embryos abortion occurred in different degrees.Compared with mature stage,the development of embryos in stone stage was better and the degree of abortion was less.Among the four female,‘Chaoyang-1’performed well that had high fruit-setting rate（28.55%）,rate of embryos（52.57%）at the stone stage and the least degree of abortion,so the compatibility of‘Chaoyang-1’was highest with the male parent.For‘Changfeng-1’,the fruits rate and compatibility and intraspecific hybridization was higher than interspecific hybridization（Prunus avium L.×P.pseudocerasus）.At the same time,the hybrid combinations of‘Zijin’and‘Chaoyang-1’male had higher rate of embryos（65.84%and 75.21,respectively）and lower embryos abortion degree.2.The mature stages of four female were different,so the embryo ages of embryo rescue were also different.‘Jiangnanhong’‘Chaoyang-1’‘Changfeng-1’‘Van’were respectively 30～38 d,37～48 d,33～41 d,32～46 d after pollination.At this time,PF value was greater than 0.5 and the germination rate of embryos was higher than 20%,which was suitable for embryo rescue.3.The germination and growth of hybrid embryos were normal after 3min sterilization with HgCl₂,which had the best effect with time saving and convenient operation.The hybrid embryos could not germinate at 5min and 8min.The best way of the low temperature stratification was puting fruits into 4℃low temperature refrigerator to storage35 d for the immature hybrid embryos.The immature embryos at stone stage of‘Changfeng-1’בChaoyang-1’as materials,germination of hybrid embryos with seed coat had slow development and rate of seedling 20.00%.After removing the seed coat,the germination rate increased to 60.00%and germination was faster,so the endopleura should be removed to ensure the germination and growth of hybrid embryos.4.Through the selecting of plant growth regulators with different proportions,the hybrid embryos rescue system for sweet cherry in southern China was preliminarily established.The suitable medium for the germination and growth of hybrid embryos was1/2 MS+6-BA 2 mg/L+IAA 1.8 mg/L.The optimal medium for‘Chaoyang-1’בGejiawu’multiplication was MS+IAA 0.4 mg/L+6-BA 0.3 mg/L.And the optimal medium for‘Chaoyang-1’בHeizhenzhu’multiplication was MS+6-BA 0.7 mg/L+IAA0.1 mg/L.The suitable medium for hybrids rootage was 1/2 MS+IBA 0.3 mg/L+IAA 1.1mg/L.5.Similar to rate of embryos,the hybrid combinations of‘Zijin’and‘Chaoyang-1’male had good germination situation and light browning degree.The mean germination rates respectively were 67.65%and 61.94%.‘Chaoyang-1’female had the least effect on the germination of hybrid embryos.It had the highest germination rate（51.82%）,growth well,rooted and the least browning degree.The female‘jiangnanhong’of hybrid embryos had the poor situation of germination with the mean rate of germination 30%and severe browning.6.The survival rate of hybrid seedlings had a certain impact by weather conditions of different transplanting stages in south warm regions.The survival rate of hybrid seedlings transplanted in mid-october was 17.50%.In mid-december,the survival rate of hybrid seedlings was highest（85.71%）,but the growth and development of hybrid seedlings were very slow.The suitable period for transplanting was mid-february,which survival rate was77.27%and plant was strong.Two weeks after transplantation to remove plastic film,the environmental conditions inside the shed are suitable with average temperature of 17℃and relative humidity of 60%.