Identification of Molecular Markers Linked to the Fertility Restorer Genes for CMS-D8 in Cotton
2004
Zhang, Jinfa | Stewart, James McD.
The identification of molecular markers closely linked to restorer genes of the cytoplasmic male sterile (CMS) D8 system could facilitate the development of parental lines for hybrid cotton (Gossypium hirsutum L.). Our objective was to develop molecular markers closely linked to the two independent dominant restorer genes, Rf₁ from the D2 restorer line transferred from G. harknessii Brandegee (D₂ genome) and Rf₂ from the D8 restorer line. Bulked segregant analysis was used to identify random amplified polymorphic DNA (RAPD) markers that were linked to the restorer genes. Three testcrosses were used for mapping Rf₂ and two for Rf₁ relative to the markers. Two RAPD markers, UBC111₃₀₀₀ and UBC188₅₀₀, were associated with Rf₂ in coupling phase. UBC188₅₀₀ was closely linked to Rf₂ with an average genetic distance of 2.9 cM. A survey of cotton species and cultivars revealed that UBC188₅₀₀ was absent in normal cotton cultivars and most Gossypium spp. However, it was present in the D8 restorer line, G. raimondii Ulbr. (D₅), G. trilobum (DC.) Skovst. (D₈), and selected wild species from Australia, indicating that Rf₂ and the DNA fragment yielding the RAPD marker were both introgressed into the tetraploid cottons from the D₈ genome. A new RAPD marker, UBC169₇₀₀, and a previously identified RAPD marker, UBC659₁₅₀₀, cosegregated with Rf₁ in the two populations examined. The three RAPD markers, UBC188₅₀₀, UC169₇₀₀, and UBC659₁₅₀₀ were converted into reliable and genome-specific sequence tagged site (STS) markers on the basis of their sequence information. These markers are restorer-specific and should be useful in marker-based selection for developing restorer parental lines and constructing a high-resolution linkage map containing Rf₁ and Rf₂
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