The cross-combination between the wild type of cotton species <i>G</i>. <i>darwinii</i> Watt with its photoperiod insensitive irradiation mutant line.

<p>A) Wild type, B) F₁ plant, and C) irradiation mutant line.</p

Genetic variances and estimated broad-sense heritability of traits in the F₃ population.

<p>Genetic variances and estimated broad-sense heritability of traits in the F₃ population.</p

The level of polymorphism of all SSR markers between parental genotypes.

<p>The level of polymorphism of all SSR markers between parental genotypes.</p

Genetic variances and estimated broad-sense heritability of photoperiod related traits in the F₂ population.

<p>Genetic variances and estimated broad-sense heritability of photoperiod related traits in the F₂ population.</p

QTL mapping for flowering-time and photoperiod insensitivity of cotton <i>Gossypium darwinii</i> Watt

<div><p>Most wild and semi-wild species of the genus <i>Gossypium</i> are exhibit photoperiod-sensitive flowering. The wild germplasm cotton is a valuable source of genes for genetic improvement of modern cotton cultivars. A bi-parental cotton population segregating for photoperiodic flowering was developed by crossing a photoperiod insensitive irradiation mutant line with its pre-mutagenesis photoperiodic wild-type <i>G</i>. <i>darwinii</i> Watt genotype. Individuals from the F₂ and F₃ generations were grown with their parental lines and F₁ hybrid progeny in the long day and short night summer condition (natural day-length) of Uzbekistan to evaluate photoperiod sensitivity, i.e., flowering-time during the seasons 2008–2009. Through genotyping the individuals of this bi-parental population segregating for flowering-time, linkage maps were constructed using 212 simple-sequence repeat (SSR) and three cleaved amplified polymorphic sequence (CAPS) markers. Six QTLs directly associated with flowering-time and photoperiodic flowering were discovered in the F₂ population, whereas eight QTLs were identified in the F₃ population. Two QTLs controlling photoperiodic flowering and duration of flowering were common in both populations. <i>In silico</i> annotations of the flanking DNA sequences of mapped SSRs from sequenced cotton (<i>G</i>. <i>hirsutum</i> L.) genome database has identified several potential ‘candidate’ genes that are known to be associated with regulation of flowering characteristics of plants. The outcome of this research will expand our understanding of the genetic and molecular mechanisms of photoperiodic flowering. Identified markers should be useful for marker-assisted selection in cotton breeding to improve early flowering characteristics.</p></div

Information of mapped SSR and CAPS markers.

<p>Information of mapped SSR and CAPS markers.</p

Genomic distributions of SSR markers and photoperiod-related QTLs identified in the F_2:3 mapping population of this study.

<p>Genomic distributions of SSR markers and photoperiod-related QTLs identified in the F_2:3 mapping population of this study.</p

Histogram of all recorded traits of flowering-time, photoperiodic flowering, other related to flowering and some morphological traits.

<p>a) flowering-time, b) node of first fruiting branch, c) number of buds, d) number of nodes, e) photoperiodic flowering, f) flowering duration Arrows show means for parental genotypes and F₁ hybrid; black arrow—wild type, white arrow—irradiation mutant, and arrow with patterned fill—F₁ plant.</p

Genetic linkage map of the F₂ population showing the location of QTL for photoperiodic flowering.

<p>Genetic linkage map of the F₂ population showing the location of QTL for photoperiodic flowering.</p