Abstract
Diversity analyses were carried out for common wheat landraces of the Xinjiang-Uyghur Autonomous District (Xinjiang) in China, which is located close to the center of diversity of cultivated wheat. Firstly, microsatellite DNA polymorphisms were analyzed by PCR using 42 kinds of primer sets in 75 landraces, 3 improved cultivars from the Xinjiang, 61 wheat cultivars from foreign countries, including neighboring ones, at the Gene Bank of the National Institute of Agrobiological Sciences through 2003 and 2004. Based on a similarity matrix calculated from coincidence coefficients of electorophoretic zymograms, principal coordinate analyses were conducted to examine differentiations between Xinjiang landraces and foreign cultivars and among Xinjiang landraces. The results of principal coordinate analyses revealed that distinctive differentiation had appeared between Xinjiang landraces and foreign wheat cultivars and also between spring and winter type wheat among Xinjiang landraces. It is considered that Xinjiang wheat landraces were genetically differentiated from foreign cultivars and that they are more closely related to cultivars from such neighboring countries as Afghanistan, Pakistan, Turkey and Russia than to those from Japan and the other parts of China. The differentiation between the spring and the winter types of wheat among Xinjiang landraces was attributed to the founder effects of their ancestors. In order to elucidate phenotypic differentiation between the spring and the winter types of wheat, six traits of 71 Xinjiang landraces, i.e. days to heading, culm length, panicle length, number of grains per panicle, number of spikelets per panicle, and 1000-grain weight were investigated at the Institute of Crop Germplasm Resources of the Xinjiang Academy of Agriculture in 2003 and 2004. Principal component analysis was conducted based on a matrix of correlation coefficients. The analysis showed that there was distinct differentiation between the spring and the winter types of Xinjiang landraces. In conclusion, Xinjiang wheat landraces were differentiated from foreign cultivars in terms of DNA polymorphism. Among Xinjiang landraces, a distinctive differentiation was also observed between the spring and the winter types in terms of agronomic traits as well as SSR polymorphisms. These differentiations are considered to be caused not only by adaptation to diverse natural and wheat-growing conditions but also by the founder effect associated with genetic differences among ancestors of Xinjiang wheat landraces.
