| Walnut(Juglans regia L.)is a perennial deciduous tree belonging to Juglandaceae family.It is a precious edible dried fruit and woody oil tree.The planting area and yield of walnut in China ranked first in the world,and more than 600 varieties have been registered.However,some cultivars have some disadvantages,such as uneven nut quality,poor stress and disease resistance.“Shimen walnut” in Hebei Province with good nut quality,strong resistance,abundant genetic resources,was known both at home and abroad.In this thesis,the germplasm resources of “Shimen walnut” were collected,the nut quality were determined,the main aroma substances and their structural characteristics of walnut fruits were analyzed,low-temperature storage test of fresh walnut and genetic diversity analysis were carried out.The main results obtained from the study are as follows:One hundred and three walnut individuals were collected and their nut quality indexes were analyzed.The appearance of most “Shimen walnut” was mainly round or near round.The range of nut weight of these walnut individuals was from 12.15 g to24.11 g,the range of kernel weight was from 5.45 g to 12.07 g,the range of kernel ratio was from 37.17% to 61.57%,the range of husk thickness was from 0.79 mm to 2.02 mm.Ten superior individuals were screened out which had the characteristics of large nut,thin husk,plump kernel,light kernel color,high content of fat,and taste fragrant and non-astringent.Thirty-five walnut resources were analyzed by SSR.The polymorphism information content of 16 selected pairs of primers ranged from 0.4810 to 0.7656,which showed high polymorphism.A DNA fingerprint was constructed using three pair of primers of WGA4,WGA276 and WGA294.The UPGMA method was used to construct the phylogenetic tree,and the 35 resources were classified into 5 groups at the genetic distance of 0.26.‘Panlongwen’ is a variety in the species of Juglans hopeiensis Hu,which was in a cluster by itself,and the individual plants and other variety resources were distributed in the other four clusters.The main aroma substances in kernel of eight walnut accessions were analyzed,a total of 29 compounds were detected in eight walnut accessions,including 11 aldehydes,4 alkanes,3 alcohols,3 esters,1 phenols,4 acids and 3 other substances.Among them,the main aroma substances are aldehydes and alkanes.There were remarkable differences in aroma components among different walnut types.Aldehydes was the main aroma substance in the walnut kernels of “Shimen walnut”,‘Liaoning No.1’ and‘Xiangling’,while alkanesis was the mainly substance in ‘Qingxiang’.In addition,the content of 1-nonanal and(2E,4E)-Undeca-2,4-dienalnonaldehyde were the rich aldehyde substance in the “Shimen walnut”.Fresh green walnut of “Shimen walnut” cultivar ‘Zaoshuo’ and control cultivar‘Xiling’ were packaged in the 0.33 mm polyethylene bags and stored in(0 ± 1)°C refrigerated warehouse.During storage,the fat content of two varieties did not change significantly.The protein content of ‘Zaoshuo’ began to decrease around 20 d,while the protein content of ‘Xiling’ began to decrease around 60 d.Combined with the changes of POD,SOD and MDA,‘Xiling’ had longer storage time than ‘Zaoshuo’.However,the water content and unsaturated fatty acid content of ‘Zaoshuo’ were higher than those of ‘Xiling’,the fresh food quality of ‘Zaoshuo’ is better. |
