Molecular Genetic Mapping of the Major Effect Photoperiod Response Locus in Pima Cotton (<i>Gossypium barbadense</i> L.)

ABSTRACT Photoperiod sensitivity is a major barrier to using introgressions from the tropical gene pool in cotton breeding programs in North America. To better understand the genetic processes underlying photoperiod response in Pima cotton, a photoperiod‐insensitive line, Pima S‐7, was crossed to a photoperiod‐sensitive landrace accession, NC7018. An F 2 mapping population of 211 individuals was used to establish that a single dominant gene controls the photoperiod sensitivity in Gossypium barbadense . Molecular mapping with simple sequence repeat (SSR) markers localized the photoperiod response gene Gb_Ppd1 to a 3.3‐cM region on chromosome 25 of the Pima cotton genetic map. Orthologous mapping of the flanking markers with the draft diploid D‐genome sequence resolved the photoperiod response gene to a 5.8 Mb region close to the centromere on chromosome 10 of Gossypium raimondii . In silico mapping of the flowering‐time candidate genes of model plant species suggested that the putative gene Gorai.010G161200 of G. raimondii , which has a function involved in photoperiodism, was mapped in the genomic region of Gb_Ppd1 . Identification of closely linked molecular markers and the delineated genomic region in sequenced G. raimondii genome will aid marker‐assisted selection and molecular isolation of photoperiod response loci in cotton.

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