Genetic diversity in Chinese endemic wheats based on STS and SSR markers
Yu-Ming Wei*, You-Liang Zheng*, Ze-Hong Yan, Wei Wu, Zhi-Qing
Zhang and Xiu-Jin Lan
Triticeae Research Institute, Sichuan Agricultural University,
Dujiangyan City 611830, Sichuan, P. R. China
Summary
The genetic diversity and genetic relationships among 40 accessions of Chinese endemic wheats, including 9 Xingjiang rice wheat (XR), 9 Tibetan weedrace (TW), 14 Yunnan hulled wheat (YH) and 8 Sichuan White Wheat (SWW), were evaluated by STS and SSR markers. In STS analysis, 11 out of 14 markers (78.6%) and 16 out of 28 marker/enzyme combinations (57.1%) revealed polymorphisms. A total of 121 bands were observed in 28 marker/enzyme combinations, with 4.3 bands per marker/enzyme combination. Thirty-nine out of 121 bands (32.2%) were polymorphic, among which 1 to 8 polymorphic bands were generated by each informative marker/enzyme combination. Among 40 Chinese endemic wheat accessions, the STS-based genetic similarity (STS-GS) ranged from 0.645 to 0.989, with the mean of 0.822. In SSR analysis, 21 out of 24 SSR makers (87.5%) showed polymorphism. A total of 83 alleles were detected. The number of alleles ranged from 1 to 7, with an average of 3.5 alleles per SSR locus. The SSR-derived genetic similarities (SSR-GS) ranged from 0.540 to 0.941, with the mean of 0.717. The cluster analysis indicated that all 40 Chinese endemic wheat accessions could be distinguished by both STS and SSR markers. The XR wheat group was genetically distinct from other three Chinese endemic wheat groups, while SWW wheaujt group was genetically related to the YH group. The TW wheat group is more diverse than the SWW and YH groups, with some accessions more related to the YH group.
Key words: genetic diversity, genetic relationship, wheat landrace,
SSR markers, STS markers
Introduction
Advances in DNA technology have greatly increased the number and type of
molecular markers available for plant genetic diversity studies. The advent
of the polymprase chain reaction (PCR) favored the development of different
molecular techniques such as random amplification of polymorphic DNA (RAPD),
simple sequence repeats (SSR or microsatellite), sequence tagged sites (STS)
and inter-simple sequence repeat polymorphic DNA (ISSR) etc. (Saiki et al. 1988;
Welsh and McCleland 1990; Williams et al. 1990; Akkaya et al. 1992; Tragoonrung
et al. 1992; Zietkiewicz et al. 1994; Nagaoka and Ogihara 1997). All these molecular
markers have been used in wheat for detecting genetic diversity, genotype identification,
genetic mapping or gene tagging (Devos and Gale 1992; He et al. 1992; Chen et
al. 1994; Talbert et al. 1994; Plaschke et al. 1995; Roder et al. 1995, 1998;
Roy et al. 1999; Prasad et al. 2000). In comparison, SSRs are more abundant,
ubiquitous in presence, hypervariable in nature and have high polymorphism information
content (Roder et al. 1995; Gupta et al. 1996). It has been shown that the use
of limited number of SSR markers is adequate to discriminate even the most closely
related wheat genotypes (Plaschke et al. 1995).
Wheat has been cultivated in China for several thousands of years, and China is rich in wheat genetic resources (Yen et al. 1988). Chinese endemic wheats include the Sichuan White Wheat complex (T. aestivum L.), the Tibetan weedrace (T. aestivum ssp. tibetanum Shao ), the Xingjiang rice wheat (T. petropavlovskyi Udacz. et Migusch.) and the Yunnan hulled wheat (T. aestivum ssp. yunnanese King) (Shao et al. 1980; Dong et al. 1981; Yen et al. 1988). Several morphological and cytogenetic studies indicated that these Chinese endemic wheats have a primitive chromosomal constitution (Riley et al. 1967; Shao et al. 1980; Chen et al. 1985, 1988; Yen et al. 1988; Yang et al. 1992). Chinese endemic wheats exhibited less RFLP diversity and low variability for both HMW-glutenins and gliadins (Dvorak et al. 1998; Ward et al. 1998; Wei et al. 2000, 2002). The objective of this paper is to evaluate the level of SSR and STS-based genetic diversity among Chinese endemic wheats.