In heterozygous fertility restored F1 plants of the CMS‐D8‐Rf2 gametophytic restoration system of cotton (Gossypium hirsutum L.), only the pollen grains with the Rf2 allele are functional; consequently, all F2 plants are fertile. Our objective was to develop a statistical method to estimate the recombination fraction (r) between Rf2 and genetic markers linked in repulsion or coupling phases in fertile F2 populations. Alleles linked to Rf2 are preferentially transmitted through pollen, whereas the transmission of alleles linked to rf2 is reduced. Thus, linked genes give distorted segregation ratios depending on the linkage strength. Genes independent of Rf show normal segregation. The traditional 3:1 or other appropriate ratios can be used to test the linkage between a marker and the Rf locus in an F2 population. Examples are given for two crosses: (D8R × T586) F2 for repulsion linkage and (D8R × T582) F2 for coupling phase linkage. The morphological data confirmed that Rf2 is not linked to nine dominant genes in T586 or to five recessive genes in T582. However, a RAPD marker, UBC188500, present in D8R and absent in nonrestoring lines, exhibited extremely skewed segregation in the D8R × T586 F2 population with only two plants without UBC188500 in a population of 76 plants. The recombination frequency between Rf2 and this marker is 5.26%, which agrees with our previous estimate from a testcross, (D8R × T586) × H1330. This indicates that the proposed method is a valid alternative for mapping gametophytic Rf2 Its advantages and limitations are discussed.
No takes yet. Share an insight, caveat, or question.
Zhang et al. (2005) studied this question.
Synapse has enriched 4 closely related papers on similar clinical questions. Consider them for comparative context: