The wild hawthorn species, Crataegus songorica K. Koch., is an important wild germplasm resource in Xinjiang, China that has been endangered in recent years.  The genetic diversity of C. songorica K. Koch. germplasm in five populations from Daxigou, Xinjiang, China were evaluated based on phenotypic traits and ISSR molecular markers to provide basic information on resource protection, rational utilization and genetic improvement.  The F-value for the phenotypic differentiation coefficient of the 33 traits measured ranged from 0.266 to 15.128, and mean value was 13.85%.  The variation among populations was found to be lower than that within population.  A total of 303 loci were detected within the five populations by 12 primers.  Within 298 polymorphic loci, the polymorphism was 98.35%, showing a high genetic diversity in C. songorica K. Koch.  The gene diversity within population, total population genetic diversity, genetic differentiation coefficient and gene flow were 0.2779, 0.3235, 0.1408, and 3.0511, respectively.  Our results showed that C. songorica K. Koch. from Xinjiang has a high level of genetic diversity at both the phenotypic and molecular levels.  Significant genetic differentiation existed within population and the differentiation trend showed a regional association.  And in this study, in situ and ex situ conservation approaches were raised for wild hawthorn protection utilization.

Fruit size is one of the most important agronomic characters, which is mainly determined by cell number and cell size. However, our current knowledge about pear is largely unknown. Through counting of pear mesocarp cells at different stages, we found that the cell number, rather than the cell size, is responsible for the differences between small- and large-fruited cultivars. Fruit weight-2.2 (fw2.2) is an important quantitative trait locus (QTL) affecting fruit weight in tomato and functions as a negative regulator in carpel cell division. To get more insights into this QTL in pear fruit development, we isolated two putative homologous fw2.2 genes, which were designated as fw2.2-like (PbFWL) genes. PbFWLs encode Cys-rich proteins with the CCXXXXCPC motif and belong to the PLAC8 superfamily. In addition, results from the subcellular localization indicated that PbFWLs were localized in the plasma membrane. The expression profile of the PbFWL genes by qRT-PCR showed they expressed higher in small-sized fruit cultivar than that in large-sized fruit cultivar during the cell division period. In summary, our data suggest that these two PbFWLs might be negatively related to the cell division in pear fruit.