Investigation,Collection And Evaluation Of Nankang Pomelo Germplasm Resources

Pomelo belongs to Citrus of the Rutaceae family.Nankang District of Jiangxi Province has a history of growing pomelo for more than 1,500 years.Nankang sweet pomelo is one of the National Geographic Mark Protection Products and a famous brand in Jiangxi Province,which is well received by consumers.However,due to the long-term irregular planting and the weak awareness of germplasm resource protection,the fruit quality of Nankang sweet pomelo has declined significantly,and the germplasm resources of Nankang sweet pomelo have also suffered a great loss.Therefore,the investigation,collection and evaluation of pomelo germplasm resources in Nankang District were carried out in this study.The main findings are as follows:1.Determination of related indexes of fresh pomelo fruit quality,including fruit weight,number of seeds per fruit,transverse and longitudinal diameter,fruit shape index,number of segments per fruit,peel thickness,edible rate,total soluble solids（TSS）,vitamin C（Vc）content,titratable acid（TA）and TSS/TA ratio.The single fruit weight of eight pomelos arrange from 1027.64g to 1855.99 g,and the coefficient of variation is 21.95%;the arrange of seed number per fruit is 46-153.67,and the coefficient of variation is 39.38%;the arrange of transverse diameter is 137.78 cm-163.32 cm,and coefficient of variation is 39.38%;the arrange of longitudinal diameter is 139.01cm-186.35 cm,and coefficient of variation is 10.69%;the arrange of fruit shape index is 0.96-1.14,and the coefficient of variation is 6.00%;the arrange of peel thickness is 11.48 cm-19.81 cm,and the coefficient of variation is 16.89%;the arrange of number of segments per fruit is 12.33-15.33,and the coefficient of variation is 6.83%;the arrange of edible rate is 36.17%-63.67%,and the coefficient of variation is 19.15%.The content of TSS is distributed between 10.40%-12.90%,and the coefficient of variation is 7.20%;the content of Vc is distributed between 45.00 mg·100 g^-1-143.56 mg·100 g^-1,and the coefficient of variation is 46.82%;the content of TA is distributed between 0.37%-0.84%,and the coefficient of variation is 32.53%;the arrange of TSS/TA ratio is13.08-32.04,and the coefficient of variation is 32.12%.2.The fruit quality before and after storage was compared.The relevant indexes of the pomelos stored at room temperature and 4℃for 40 days were measured,including color difference,peel thickness,edible rate,TSS,Vc,TA,TSS/TA ratio and water loss rate.The results revealed that the value of L*,a*,b*of most pomelos showed an increasing trend,and the L*,a*,b*value of pomelos stored at room temperature changed more than the pomelos stored at 4℃.Other indicators were similar.3.Seventeen primers were selected from 100 ISSR primers.The DNA of eight pomelos was used as templates for PCR,and 183 clear bands were amplified,of which 159 were polymorphic,and the average percentage of polymorphic bands was 87.10%.The genetic similarity was between0.48-0.78.When the similarity coefficient was 0.67,eight pomelos were divided into three categories.The results indicated that 8 pomelos had relatively high genetic diversity,which could be used as materials for hybrid breeding,genomics research,and comprehensive utilization.4.Essential oils from the peels of Shatian pomelo,Lianjia pomelo and crystal pomelo were extracted.When the substance similar was set≥900,totally 49 substances were identified from the3 kinds of pomelo peel essential oils.The main component of the OPLS-DA model was adopted.The differentially accumulated components among the three pomelos’essential oil were identified when the variable projection importance（VIP）was greater than 1 and the P value of the t test was less than 0.05.The differentially accumulated components of Lianjia pomelo and Shatian pomelo were:butylated hydroxytoluene,1-isopropyl-4,7-dimethyl-1,2,3,4,5,6-hexahydronaphthalene,two phthalate butyl ester,methyl salicylate,dextrogenous myrcene,β-caryophyllene,trans-linalool oxide（furan）,bicyclic geranene,geranyl acetate,and nocaketone.The differentially accumulated components between crystal pomelo and shatian pomelo were:butylated hydroxytoluene,1-isopropyl-4,7-dimethyl-1,2,3,4,5,6-hexahydronaphthalene,dibutyl phthalate Esters,methyl salicylate,geraniol,nerol,indole,linalool.The differentially accumulated components of Lianjia pomelo and crystal grapefruit were:butylated hydroxytoluene,dextrogenous myrcene,β-caryophyllene,trans-linalool oxide（furan）,geraniol,nerol,indole,（E,E）-farnesol,citral,orange aldehyde.