Abstract: In order to analyze the genetic diversity of Tibetan yaks, 10 pairs of primers were selected from ISSR primer library and used to analyze 17 groups (species), with a total number of 850 yaks, by PCR amplification. The obtained statistical data were also analyzed by Popgen 32 software. The results showed that 10 pairs of ISSR primers amplified a total of 134 bands including 132 polymorphic bands. The polymorphism ratio is 95% and the size of the amplified fragment ranges from 200 to 2000 bp. The average effective number of alleles of 17 yak groups is 1.498, the mean index of Nei’s genetic diversity is 0.294 and average Shannon diversity index is 0.449. Clustering results show that Tibetan yaks are roughly divided into three categories: The first group includes Cuona yak, Jiangda yak, Gongbujiangda yak, Kangbu yak, Baqing yak, Leiwuqi yak, Sangsang yak, Jiali yak, Sibu yak and Longzi yak; the second includes Dingqing yak, Nierong yak, Pali yak, Riduo yak, Sangri yak and Shenza yak; the third group only includes Zhongba yak. Cluster analysis results are basically consistent with the geographic distribution of yaks.

Key words: straw mat, agricultural carpet, root-zone soil, nitrate metabolizing., apple, mulching