Construction Of Hybrid Populations Of 20 Germplasms Of Chinese Cherry(Cerasus Pseudocerasus(Lindl.) G.Don),and Identification And Cultivation Of Their Hybrid Springs

Chinese cherry[Cerasus pseudocerasus（Lindl.）G.Don],is an important deciduous fruit tree with highly ornamental and economic values.As a traditional fresh fruit with fabulous flavor,the drupes contain rich nutritional ingredients and trace elements rich nutrition,which has been known as“treasures of fruit”and“earliest fruit in spring”.Over a long time of domestication,large numbers of excellent variations have been deposited in landraces for the adaptation to various harsh environmental conditions.These landraces contain greater genetic diversity than elite cultivars and represent an intermediate stage in domestication between wild and elite cultivars.In the past few decades,Chinese cherry has become an important medium for the rapidly developed rural tourism.The business is also booming throughout its distribution due to its alluring daintiness,disease resistance and graceful flowers.However,with the improvement of living standards and the impact of market competition,the requirement for fruit quality of Chinese cherries becomes more demanding.The characters such as small fruit size,similar mature period and intolerance of storage and transportation have restricted its development.In addition,due to the small seeds,hard endocarp,difficult seedlings of hybrid,long breeding cycles,and slow of molecular-assisted breeding,as well as limited researches of genetic maps,breeding is mainly focused on the landraces.The new varieties from cross breeding is extremely low,the renewal of good varieties is relatively slow.Therefore,in this study,excellent and representative resources were selected for hybridization based on the phenological phase and quality analyses of landraces collected in recent years.Identification of hybrid was also conducted use SSR molecular markers,the germination of Chinese cherry seeds were processed using physical and chemical methods.It applies different combinations of NPK and different concentrations of compound fertilizers to cultivate the hybrid seedling,increase the survival rate,shorten the breeding cycle,provide reliable materials for molecularly assisted breeding,and speed up the breeding process.The main findings are as follows:i Selection of Cross-parentThis study investigated the phenology period,quality analysis and genetic cluster of twenty Chinese cherry landraces.Due to the short blossoming period of Chinese cherry（lasted for 5 to 10 days）we preserve the pollen grains temporarily early blossoming to avoid asynchronism in blossoming time.The peels of Heizhenzhu（HZZ）and Hongfei（HF）were dark purple and fuchsia,while Nanzaohong（NZH）was orange red and（Pengzhoubai）PZB was yellow,respectively.HF and Pujianghonghua（PJHH）revealed different fruit size.There were significant genetic difference of fruit shape and fruit top shape among HF,HZZ and NZH germplasms.HF showed the best econimic performance with large fruits,high soluble solids,and deeper skin color,exhibting excellent potentiality of cherry breeding.We selected these germplasms with excellent economic traits and significant genetic difference to cultivate hybrid varieties.These choosen hybridization combinations were HF×NZH,HF×MY5,HF×PJHH,HF×PZB,NZH×HF,PZB×HF,and HZZ×PZB.ii Construction of hybrid populationsPollen vigor,fruit setting rate and fruit quality analyses were performed on the seven cross combinations.Finally,SSR markers were performed to identify the true hybrids.The PZB and MY5 revealed relatively low levels of pollen viability,resulting in the low fruit setting rate of the hybridization as male parent.Those combinations with PJHH as male parent showed the highest fruit setting rate.Based on fruit quality analysis,different male parents had significant influence on the content of total soluble solids and total acids of the fruits when using HF as female parent.Among them,the highest total soluble solids exhibited in the cross of HF×NZH and HF×MY5,while the highest total acids in the cross of HF×PZB.There was no significant difference between natural growth and self-cross for the remaining cross combinations.Five pairs were selected from twenty pairs of SSR primers to amplify the bands of the cross parents and hybrid populations.129 hybrid plants could be identified to be true hybrids by five pairs of primers,while 124 were identified by five pairs complementally.Thus,253 hybrid plants were all true hybrids of’HF×PJHH’.iii Cultivation of hybrid seedlingAccording to the treatment of endocarp-pelt,stored in low temperature sand and gibberellin on the hybrid seeds,the treatment with endocarp-pelt+stratified+gibberellin had the most significant improvement for the germination rate of hybrid seedlings.The germination rate of the hybrid seeds was 78.67%of endocarp after soaking in low temperature sand for seven days with 100 mg·L^-1 gibberellin.Different ratios of nitrogen（N）,phosphorus（P）and potassium（K）and different concentrations of compound fertilizer were used to fertilize hybrid seedlings.The results showed that the optimal nitrogen,phosphorus and potassium formulas for seedling height growth was N₂P₂K₃,and the best growth formula for ground diameter was N₃P₃K₅,for height-diameter ratio was N₁P₃K₃,for chlorophyll content and net photosynthetic was N₂P₅K₁.The combination with the highest rate was N₂P₅K₁.The best effect of stomata conductance on hybrid seedlings was N₂P₅K₁.Considering the effect of hybrid seedlings on growth and photosynthetic physiology,the order of impact was potassium,followed by nitrogen and phosphorous.The most economical and efficient formula for hybrid seedling growth was N₂P₂K₃.The nitrogen,phosphorus and potassium were 1 g,1 g and 0.5 g for each hybrid seedling.The best effect of different concentrations of compound fertilizer on the growth of hybrid seedlings was 4 g·tree^-1;the 4 g of compound fertilizer was used per plant.