Phenotypic Analysis Of 203 Pear Germplasm Resources

Shandong Province is one of the main pear producing areas in China,with abundant wild and semi wild varieties,providing high-quality pear germplasm resources for long-term human selection,domestication,and cultivation.By understanding the growth and development of different pear cultivars in Shandong Province and provide excellent cultivar resources for field production and breeding work.This study used 203 pear germplasm resources from the pear germplasm resource nursery of Shandong Agricultural University in Feicheng District,Shandong Province as experimental materials to investigate and analyze the morphology and growth habits of branches,buds,leaves of different pear cultivars.The results are as follows:1.A survey of the growth habits and the morphology of branches,buds,and leaves of different pear cultivars found that the color of the annual branches was mainly brown,followed by red brown,and the black brown varieties were the least;The number of lenticels on one-year-old shoot mainly include many;The majority of cultivars have no thorn on their branches;The leaf buds adpressed most,followed by slightly held out,and markedly held out least;The pear cultivars which had acute at apex of vegetative bud is larger than the obtuse cultivars;The size of bud support was mainly small;Most cultivars had no pubescence on flower bud;The leaf shape was mainly ovate and elliptic;The shape of leaf base was mainly round and wide wedge-shaped;The shape of leaf apex is mostly sharp-acuate;The leaf margin is most serrate in number;All cultivars had no crack on leaves;There are more cultivars with seta on leaf margin;The tree habit is mainly upright and spreading;The bark character of trunk was mainly smooth;Pyrus communis L.have the smallest flower bud length,petiole length,leaf length,leaf width,and internode length,while Pyrus bretschneideri Rehd.have the largest flower bud length,petiole length,and leaf length,while Pyrus pyrifolia Nakai.has the largest leaf width and internode length.2.Correlation analysis was conducted on the branches,buds,leaf shapes,and growth habits of different pear cultivars.It was found that there was a significant positive correlation between the length of flower bud and petiole length,leaf length,petiole length and leaf length,leaf width,and leaf length and leaf width.There was a significant negative correlation between length of internode and leaf length and leaf width.The position of vegetative bud in relation to shoot and the size of the bud support,the leaf margin and the shape of leaf base,and the presence or absence of seta on leaf margin were significantly positively correlated with the shape of the leaf base and the presence or absence of seta on leaf margin.There was a significant negative correlation between leaf shape and shape of leaf base,the presence or absence of seta on leaf margin,and between bark character of trunk and the presence or absence of seta on leaf margin.3.Principal component analysis was conducted on five quantitative traits of pear germplasm resources,including length of flower bud,petiole length,leaf length,leaf width,and length of internode.Four principal components were extracted,with a cumulative contribution rate of 92.350 %,which can reflect most of the information on quantitative traits of pear branches,buds,and leaves.4.Cluster analysis was conducted on the four quantitative characters of length of flower bud,leaf length,leaf width and length of internode of pear germplasm resources and seven qualitative characters of position of vegetative bud in relation to shoot,character of apex of vegetative bud,leaf shape,shape of leaf base,shape of leaf apex,leaf margin,and the number of lenticels on one-year-old shoot.They were divided into nine categories at the square European distance of 8.50.The phenotypic characters of pear germplasm resources of different groups had certain differences.5.In order to select dwarf varieties,two pear germplasm resources with shorter internode length were selected from 203 pear germplasm resources based on the phenotypic traits of internode length: ‘Tetraploid Red Bartlett pear’ and ‘Call.C’,which can be used as candidate varieties for dwarf close planting cultivation,achieving premature birth and high yield of fruit trees,and also as hybrid parent materials for dwarf breeding.