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1、遗遗 传传 学学 报报 Acta Genetica Sinica, August 2006, 33 (8)：733745 ISSN 0379-4172 Genetic Diversity of Source Germplasm of Upland Cotton in China as Determined by SSR Marker Analysis CHEN Guang, DU Xiong-Ming Key Laboratory of Cotton Genetic Improvement of Agricultural Ministry, Cotton Research Institute,
2、 Chinese Academy of Agricul-tural Sciences, Anyang 455004,China Abstract: The genetic diversity of 43 sources of Upland cotton germplasm with different parental origins, breeding periods, and ecological growing areas in China were studied on the basis of simple sequence repeat (SSR) markers. A total
3、 of 130 gene alleles with 80% polymorphism were detected from 36 SSR primers. The number of alleles per primer ranged from two to eight with an average of 3.6. The polymorphism information content (PIC) range was 0.278-0.865, with an average of 0.62. The average geno-type diversity index (H) was 1.1
4、02, the highest was 2.039 and the lowest was 0.451. The average coefficient of the genetic similar- ity of SSR markers among source germplasm was 0.610, ranging from 0.409 to 0.865. These indicated that the genetic diversity at the genomic level of the selected source germplasm was rich, and was rep
5、resentative of the diversity of the germplasms, in general. The diversity at the genome level of the base germplasm from the second and third breeding periods was decreased compared to that of the first period, indicating that the cotton genetic background in China became narrow gradually. The diver
6、sity of SSR markers among the base germplasm from early maturity cotton growing areas in the north was higher than those from the Huanghe and Yangtze growing areas. The molecular marker genetic similarity index of the domestic varieties was higher than that in the introduced varieties, which indicat
7、es that the genetic diversity in domestic cultivars was lower than that in the introduced varieties. This study gives an overview of the genetic diversity of the cotton germplasm base in China, and provides a guide for breeders to develop new cultivars efficiently. Key words: source germplasm; SSR;
8、genetic diversityReceived: 2005-09-07; Accepted: 2005-12-19 This work was supported by the 10th Five Years Key Programs for Science and Technology Development of China (No. 2004BA525B05). Corresponding author. E-mail: ; Tel: +86-372-2525 352 Source germplasm for cotton (Gossypium hirsu- tum L.) bree
9、ding in China includes germplasms with stable genetic characters, excellent yield, adaptability, and better general combining ability, and have been used frequently as parents in many breeding pro- grams. There are few reports on source germplasm research. Huang 1 described in the book “Cotton Varie
10、ty and Pedigree in China” 36 source germplasms from the G. hirsutum varieties, comprising 25 foreign varieties, eight Chinese varieties and three varieties with low gossypol. Du and Liu 2 described a new method of classification of source germplasm by emphasizing the number of derived varieties in a
11、ddi- tion to their pedigrees. The authors defined the source germplasm as being lines or varieties from which 20 or more applied varieties have been derived. Accord- ing to this criterion, 47 germplasm sources of Upland cotton used in China were described, which include 16 foreign varieties, 29 Chin
12、ese varieties, and two varieties with low gossypol. Genetic diversity is the basic portion of biological diversity and is the base of biological polymorphism and species diversity. Genetic diversity and parenthood of germplasm play an important role in cotton breeding. The precise evaluation of the
13、genetic diversity of excellent germplasm will provide a guide for choosing parents and predicting the degree of inheritance, variation, and level of heterosis, which are essential for realizing the breeding 734 遗传学报 Acta Genetica Sinica Vol.33 No.8 2006 goal. Molecular marker analysis is a modern te
14、chnique, which discloses genetic differences at the DNA level in plants and is an effective tool for testing genetic diversity of germplasm in breeding programs 3, 4. The study of cotton germplasm diversity has expanded from the phe- notypic, cellular, and biochemical levels to the DNA level. Modern
15、 molecular marker techniques can illuminate the individual differences and relationships among species at the DNA level. Most cotton varieties planted in China were derived from a few sources of germplasm such as DPL, Stoneville, King, Uganda, Foster, and Trice, all of which were introduced from abr
16、oad. These varieties were the foundation of Chinese cotton breeding programs and played a decisive role in the self-breeding varieties of China. It has been indicated that the genetic base was narrow and the genetic diversity was low in Upland cot- ton in China. This was caused by a limited quantity of source germplasms. We will present evidence from mo- lecular marker analysisshowing the correlati
