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Genetic diversity of Pakistani cotton cultivars as revealed by simple sequence repeat markers.

Khan, A.I., Fu, Y.B., and Khan, I.A. (2009). "Genetic diversity of Pakistani cotton cultivars as revealed by simple sequence repeat markers.", Communications in Biometry and Crop Science, 4(1), pp. 21-30.


Cotton (Gossypium hirsutum L.) is the most important cash crop of Pakistan. More than 80cotton cultivars have been developed since 1914 through conventional breeding, but nocomprehensive study has been made on the genetic diversity of these cultivars. Simplesequence repeat (SSR) markers were used to assess the genetic diversity of 40 representativecotton cultivars released from 1914 to 2005. Thirty-four of the 57 SSR primer pairs screened displayed polymorphism and 122 of the 204 SSR bands detected by these polymorphic primerpairs were polymorphic across the cultivars. The frequencies of these polymorphic bands ranged from 0.02 to 0.98 and averaged 0.27. Analysis of molecular variance revealed 12.4% ofthe total SSR variation residing among the cultivars over five specified breeding periods. The cotton cultivars released after 2000 displayed slightly more SSR variation than those releasedearlier. Clustering 40 cultivars resulted in three major clusters mixed with cultivars releasedfrom various breeding periods at different research stations. The average dissimilarity (AD)of a cultivar ranged from 0.191 to 0.365 with the mean AD of 0.248, and genetically distinctcultivars were identified. These results are useful for conserving elite cotton germplasm anddeveloping future cotton breeding programs in Pakistan.

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