Study On The Change And Regulation Of Acid Content And Hereditary Tendency Of Chinese Dwarf Cherry Germplasm

Chinese Dwarf Cherry [Cerasus humilis(Bge.)Sok.]is a member of Cerasus genus in rosaceae family,which is one of the peculiar fruiting shrub resource in China.Organic acids play an irreplaceable role in the formation of fruit quality.Chinese Dwarf Cherry is rich in Germplasm resources.The content of organic acids in fruit is not only affected by differences germplasm,but also by other organs,cultivation conditions and environmental conditions.In this study,the titratable acid(TAC),soluble solids(SSC)and other fruit characteristics of 206 germplasm in Chinese Dwarf Cherry germplasm garden of Shanxi Agricultural University were determined,and the changes of TAC in germplasms with different TAC during four fruit developmental stages were observed.Effects of treatments(leaf-fruit ratio adjustment,shading and spraying leaf surface fertilizer)on TAC and SSC in fruit were studied,and the genetic variation tendency of TAC and SSC in fruit of Hybrid Progenies of Chinese Dwarf Cherry was analyzed,which provides a basis for scientific evaluation of germplasm and variety improvement of Chinese Dwarf Cherry.The main results are as follows:1.According to the clustering thermogram analysis of acid content,206 Chinese Dwarf Cherry germplasms were divided into four acid types: type 1: low acid type(TAC ranges 0.50%-1.18%,a total of40 germplasms),type 2: medium acid type(TAC ranges 1.19%-1.58%,a total of 84 germplasms),type 3:medium-high acid type(TAC ranges 1.59%-2.24%,a total of 71 germplasms),and type 4: high acid type(TAC ranges 2.25%-2.85%,a total of 11 germplasms).2.During the four fruit developmental stages(Fruit expansion period,Color transfer period,Coloring period,mature period),varieties with different TAC had a similar pattern of TAC increasing firstly and then decreasing.However,the initial acidity,the period during which the highest TAC peak occurred,and the magnitude of the increase and decrease of the TAC showed large differences.Firstly,high acid type(Y03-09)was significantly higher than medium acid type(09-03),medium acid type(Nongda 6,Nongda 7),low acid type(DS-1,10-06)at the stage of fruit enlargement,which means high acid type had higher acid accumulation than that of low acid type in early stage.Secondly,for low-acid cultivar `10-06',its peak TAC appeared earlier(about 10d)than other germplasms,making it have two acid-reducing periods.Futhermore,the low-acid varieties have larger TAC reduction.Therefore,the acidity of mature fruit is determined by the accumulation and the degradation of organic acids.TAC of Chinese dwarf cherry germplams showed a certain correlation with fruit SSC and ratio of total soluble solidstitratable to titratable acid(RTT).For the low TAC germplams,TAC was negatively correlated to SSC(p<0.05)and RTT(P <0.01),respectively.For the medium TAC germplams,TAC was positively correlated with SSC and negatively correlated with RTT(P <0.01).For the medium-high TAC germplams,TAC were positively correlated with SSC and negatively correlated with RTT.For the high TAC germplams,TAC was positively correlated with SSC and RTT.TAC was positively correlated with SSC and negatively correlated with RTT during fruit developmntal stages.Moreover,correlations reached to a significant level during the FES and CCS.4.Different treatments of leaf-fruit ratio adjustment posed a great impact on the fruit TAC and SSC of varieties 'Nongda 6' and 'Nongda 7'.The TAC of these two varieties decreased when the increasing their leaf-fruit ratio,however,for each variety,different leaf-fruit ratios had no significant effect on fruit TAC;Both SSC and RTT increased when the leaf-fruit ratio increased.For 'Nongda 6' and 'Nongda 7',their optimized leaf-fruit ratio were 6:1 and 10:1 respectively,at which TAC was reduced and SSC was increased.The shading treatment of 'Nongda 6' and 'Nongda 7' showed that the average fruit TAC and the fruit SSC were reduced under 60 % and 80 % of shading.Spraying different leaf surface fertilizers caused different results : For variety 'Nongda 4',both spraying sodium dihydrogen phosphate(2 times)and spraying ammonium molybdate(3 times)resulted in reduced TAC and improved RTT.For variety 'Nongda 6',The application of sodium dihydrogen phosphate(2 times)or ammonium molybdate(2 times)can significantly reduce the fruit TAC and improve the RTT.However,the application of sodium dihydrogen phosphate and ammonium molybdate had no obvious effect on the fruit TAC and the RTT of variety 'Nongda 7'.5.Progenies of `Nongda 6'×`Nongda 7',`DS-1'×`Y03-09',`DS-1'×`99-02' showed obvious continuous variation on the fruit TAC,which suggested that the inheritance of TAC was a quantitative trait controlled by polygenes.F1 generation showed a partial normal distribution,suggesting that TAC might be a complex inheritance controlled by one or more major and minor genes.F1 generation showed a continuous variation of SCC which were also normally distributed,indicating that SSC was a quantitative trait controlled by micro-effect polygenes.The variation coefficients of TAC in F1 generation of three combinations were higher than those of SSC,which indicated that TAC had greater selection potential than SSC.SSC of'Nongda 6'× Nongda 7' progenies tended to higher than the average value of their two parents,while TAC tended to be lower than their two parents Both SSC and TAC of 'DS-1'×'99-02' and 'DS-1'× 'Y03-09'progenies tended to be higher than the average value of their two parents,and therefore breeding of a new variety with lower acidity than 'DS-1' was less likely.On the other hand,it will be easier to select high SSC varieties.