Analysis Of Genetic Diversity And Genetic Relationship Of Fortunella And Its Relatives

Kumquat is a perennial,whose fruits can be eaten freshly or processed and which can be used as ornamentals.Kumquat germplasm resources contain abundant excellent genes and are the potential germplasm basis of kumquat breeding.To better dig and use the kumquat resources,this research collected 34 Fortunella Swingle resources,including wild germplasm,variation of cultispecies and their relatives.They are used as materials to evaluate and analyze the morphological characteristics,floral phenological characteristics,fruit quality characteristics and pollen characteristics of kumquat,and to screen excellent germplasm.This study can provide scientific basis for the breeding,development and utilization of kumquat.The main results are as follows:1.The basic morphology of the leaves is generically specific.The leaf morphology of Fortunella,Citrus and Poncirus is different,and the common characteristics of Fortunella and Citrus are more than those of Poncirus.According to the fruit appearance including pericarp color,fruit shape,shape of fruit top and shape of fruit botton,the varieties with a good appearance widely favored by consumers were screened out,such as F.crassifolia Swingle.huapijingan and F.crassifolia Swingle.Rongancuimi.Their appearance characteristics were the smooth fruit surface,the spherical fruit shape,and the orange pericarp color.2.According to the 2019 phenological records,the length of flower cycle was significantly affected by temperature.The flowering period is short when the temperature is high and long when the temperature low.Kumquat blooming time was in April,June,July,August,September,October and November respectively,and flowering times were 4 to 7times,with no significant difference among different varieties.The flowering times of Poncirus are few,flowering 1?2 times in a year.The mature period of kumquat is affected by the climate.The mature period of the same cultivar may be delayed or advanced because of the different environment and climate,which can provide theoretical reference for the cultivation of early maturing varieties or late maturing varieties.3.According to the analysis of the main components of fruit quality,the first component has sugar-acid ratio,ratio of TSS to TA,TSS,soluble sugar and TA,and the variance contribution rate is 46.51%.The second main component has content and fruit shape index and the variance contribution rate is 18.236%.The third main component is the Vc content and the variance contribution rate is 15.364%.The cumulative variance contribution rate of these three principal components reaches 80.11%,basically reflecting the most initial information of the eight quality indicators of 23 test varieties.It indicates that sugar-acid ratio,ratio of TSS to TA,TSS,soluble sugar and TA can be used as the main factors for the quality evaluation of kumquat.According to the comprehensive evaluation and sorting of fruit quality,the overall quality of F.crassifolia Swingle.Ningbojindan CS,F.crassifolia Swingle.rongancuimi,F.crassifolia Swingle.huapijingan and F.crassifolia Swingle.liuyangjingan No.4 is higher than other varieties.They have high TSS content,low TA content and high soluble sugar content,vitamin C content and higher edible rate.Relatively speaking,F.obovata Tanaka shouxingju,C.madurensis sijiju CS,F.obovata Tanaka wenguangju,F.japonica(Thunb)Swingle.Ningboluowen CS,and Fortunella Swingle.yeshengjingan are of lower quality and less competitiveness.Through the principal component analysis combining the internal quality factor and some external quality factor of fruit,this experiment preliminarily constructed a relatively convenient and intuitive method for screening excellent fruits.The results can lay a theoretical foundation for the construction of kumquat evaluation system.4.The morphological characteristics of pollen of 34 different cultivars of Fortunella,Citrus and Poncirus were observed by scanning electron microscope(SEM).The results showed that the 34 materials could be divided into four branches when the distance was10.The first branch mainly includes Citrus,Fortunella materials with low evolutionary status,and hybrids of Fortunella and Citrus.The F.crassifolia Swingle in the second branch has a higher evolutionary status than the first branch.The third branch is characterized by the largest pollen grain,the largest mesh,and the narrowest mesh ridge width,which belongs to the material with the lowest evolutionary status.The fourth branch consists of F.crassifolia Swingle.huapijingan and the F.crassifolia Swingle.suichuancuimi,which are the two most widely used varieties.The results could provide basis for the relationship and identification of different kumquat species.