Gardunia, Brian Wayne (2006-12). Introgression from Gossypium mustelinum and G. tomentosum into upland cotton, G. hirusutum. Doctoral Dissertation. Thesis uri icon

abstract

  • To increase genetic diversity with elite upland cotton, introgression populations
    with wild species of cotton, Gossypium mustelinum and G. tomentosum, were created.
    To accomplish this objective, F1, F2, BC1F1, and BC1F2 generations were developed
    along with random mating populations (BC1rm1 and BC1rm2) and grown in a
    randomized complete block design with four replications in College Station, Texas
    during 2003 and 2004, and in Mexico during 2005 for G. mustelinum introgression
    populations. These generations were tested with microsatellite markers from
    chromosome 11 in order to measure the effects of selection and recombination. Later
    generations (BC2F1, BC2rm1, BC2F2, BC3F1, BC3rm1 and BC3F2) and composite
    generations were evaluated in a randomized complete block design with four replications
    during 2004 and 2005 for agronomic properties.
    Introgression barriers for G. mustelinum were found to include daylength
    sensitivity and hybrid breakdown, which was only apparent in Mexico. Backcross
    generations had improved fiber quality. Random mating populations did not have
    increased variance and means differed little from BC1F1 levels. Microsatellite markers showed decreased frequency of G. mustelinum alleles and decreasing heterozygosity, but
    no increase in map distances in random mating populations. Upper-half mean length and
    upper quartile length by weight were highly heritable, as measured with parent-offspring
    regression. Most other agronomic traits had moderate heritabilities. Composite
    generations were found to be favorable for selection and breeding.
    For G. tomentosum populations, hybrid breakdown was also a problem with low
    yields for F2 and BC1F2 generations, but day length sensitivity was not. Little or no
    increase in variance was found in random mating populations when compared to BC1F1
    levels. G. tomentosum populations did not show improvements in fiber length as seen in
    G. mustelinum populations, but did have increased strength in BC1F1 and F1
    generations over TM-1. Mapping distances increased in the random mating populations
    for G. tomentosum, and the frequency of alien alleles did not decrease in random mating
    populations. Generation means approached recurrent parental values for most traits
    within three backcrosses. Composite generations were found to be the most useful for
    breeding and selection.

publication date

  • December 2006