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薄壳山核桃是重要的木本油料作物.'波尼'、'马罕'、'金华'、'钟山25'都是中国大面积推广种植的优良品种.本研究采用常规染色体压片法,以薄壳山核桃嫩芽为材料,对该4个主要栽培品种进行核型分析.结果表明,薄壳山核桃的染色体为2n=32.4个无性系品种的核型类型都是2B.'波尼'染色体组成为2S+ 16M1+12M2+2L,核型公式为2n=32=12sm+18m+2T;'马罕'染色体组成为6S+12M1+8M2+6L,核型公式为 2n=32=16sm+14m+2T; '金华'染色体组成为 4S+12M1+14M2+2L,核型公式为 2n=32=10sm+20m+2T; '钟山25'染色体组成为6S+12M1+8M2+6L,核型公式为2n=32=8sm+22m+2T.4个无性系品种的核型不对称系数分别为62.07％、64.68％、62.47％、62.38％.从进化角度来看,'波尼'属于比较原始的类型,'马罕'属于比较进化的类型.本研究可为薄壳山核桃种质资源鉴定和育种提供细胞学基础.“,”Pecan (Carya illinoinensis) is an important woody oil crop. 'Pawnee', 'Mahan', 'Jinhua', 'Zhongshan25' are all fine varieties that have been promoted to cultivate in large scale in China. The chromosome numbers and karyotypes of four pecan cultivars were studied by applying traditional squash technique. The results showed that the chromosome number of all tested cultivars was 32. The karyotypes of four kinds of Carya illinoinensis were 2B. The results indicated that the karyotype formula of 'Pawnee' was 2n=32=12sm+18m+2T, chromosome composition of relative length was 2S+16M1+12M2+2L; and the karyotype formula of 'Mahan' was 2n=32=16sm+14m+2T, chromosome composition of relative length was 6S+12M1+8M2+6L; as to 'Jinhua', the karyotype formula was 2n=32=10sm+20m+2T, the chromosome composition of relative length was 4S+12M1+14M2+2L, the last one is 'Zhongshan25', the karyotype formula was 2n=32=8sm+22m+2T, the chromosome composition of relative length was 6S+12M1 +8M2+6L. These index of kary otype asymmetries of four pecan cultivars were 62.07％, 64.68％, 62.47％, 62.38％. 'Pawnee' was relative original while 'Mahan' was evolutional during genome evolution. This study could provide cytological basis for the identification and breeding of germplasm resource of pecan.