REGULAR ARTICLE
Genetic diversity of Pakistani cotton cultivars as revealed by simple sequence repeat markers
Azeem I. Khan, Yong-Bi Fu, Iftikhar A. Khan
Communications
Biometry Crop Science (2009) 4 (1), 21-30.
ABSTRACT
Cotton (Gossypium hirsutum L.) is the most important cash crop of Pakistan. More than 80 cotton cultivars have been developed since 1914 through conventional breeding, but no comprehensive study has been made on the genetic diversity of these cultivars. Simple sequence repeat (SSR) markers were used to assess the genetic diversity of 40 representative cotton 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 primer pairs 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% of the 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 released earlier. Clustering 40 cultivars resulted in three major clusters mixed with cultivars released from 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 distinct cultivars were identified. These results are useful for conserving elite cotton germplasm and developing future cotton breeding programs in Pakistan.
Key Words: Gossypium hirsutum; genetic diversity; genetic relationship; genetic distinctiveness; Simple Sequence Repeat (SSR) marker.
