Abstract
Pecan is an important horticultural nut crop originally from North America and now widely cultivated in China for its high ecological, ornamental and economic value. Currently, there are over one hundred cultivars grown in China, including introduced American cultivars and Chinese seedling breeding cultivars. Molecular markers were used to assess the genetic diversity of these cultivars and to identify the pedigrees of fine pecan plants with good characteristics and no cultivar-related data. A total of 77 samples grown in China were studied, including 14 introduced cultivars, 12 domestic seedling breeding cultivars, and 49 fine pecan plants with no cultivar data, together with Carya cathayensis and Juglans nigra. A total of 77 ISSR and 19 SSR primers were prescreened; 10 ISSR and eight SSR primers were selected, yielding a total of 94 amplified bands (100% polymorphic) in the range of 140–1,950 bp for the ISSR and 70 amplified bands (100% polymorphic) in the range of 50–350 bp for SSR markers. Genetic diversity analyses indicated Chinese-grown pecan cultivars and fine plants had significant diversity at the DNA level. The dengrograms constructed with ISSR, SSR or combined data were very similar, but showed very weak grouping association with morphological characters. However, the progeny were always grouped with the parents. The great diversity found among the Chinese cultivars and the interesting germplasm of the fine pecan plants analyzed in this study are very useful for increasing the diversity of the pecan gene pool. All 77 accessions in this study could be separated based on the ISSR and SSR fingerprints produced by one or more primers. The results of our study also showed that ISSR and SSR techniques were both suitable for genetic diversity analyses and the identification of pecan resources.
Highlights
Pecan (Carya illinoensis) is a North American deciduous tree that belongs to the Juglandaceae family, which includes hickories, walnuts and the Carya genus, which comprises approximately25 species of large trees
The dengrograms constructed with inter-simple sequence repeat (ISSR), simple sequence repeat (SSR) or combined data were very similar, but showed very weak grouping association with morphological characters
The great diversity found among the Chinese cultivars and the interesting germplasm of the fine pecan plants analyzed in this study are very useful for increasing the diversity of the pecan gene pool
Summary
Pecan (Carya illinoensis) is a North American deciduous tree that belongs to the Juglandaceae family, which includes hickories, walnuts and the Carya genus, which comprises approximately. From previous studies of pecan, it is clear that these molecular marker techniques were only focused on the American pecan cultivars, whereas the Chinese-grown pecans, which are very suited to the local climate and possess many great characters, were not investigated. Both inter-simple sequence repeat (ISSR) and SSR markers based on the polymerase chain reaction (PCR) are commonly used for measuring genetic diversity [16,17] and for cultivar identification [18,19]. These results should provide useful data for further breeding programs
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