Dighe, Nilesh Deoram (2007-12). Introgression of reniform nematode resistance and other germplasm from G. longicalyx and G. armourianum into G. hirsutum. Doctoral Dissertation. Thesis uri icon


  • The Gossypium genus includes 45 diploid and 5 tetraploid cotton species of which only
    2 diploids and 2 tetraploids are cultivated in different parts of the tropics and sub-tropics,
    leaving the remaining diploid and tetraploid species as potential genetic sources for
    novel trait introgression. The reniform nematode (Rotylenchulus reniformis Linford and
    Oliveira) poses significant problems to US cultivated Upland cottons (Gossypium
    hirsutum L., 2n=52), all of which lack high resistance. This work was in collaboration
    with the USDA-ARS team that focussed on introgressing reniform nematode-resistance
    from a diploid cotton species, Gossypium longicalyx Hutch. & Lee into G. hirsutum by
    creating a tri-species hybrid, HLA and backcross breeding (Bell et al., 2007; Robinson et
    al., 2007). The main objectives of this work were [1] to cytogenetically evaluate and
    help select superior types at each introgressed generation; [2] to identify molecular
    markers tightly linked to the reniform nematode-resistance gene and to map the
    resistance loci; [3] (A) to introgress germplasm on a genome-wide basis, (B) to evaluate
    introgressed germplasm for traits of economic importance other than reniform nematode
    resistance, and (C) to evaluate breeding methodologies in terms of this specialized
    breeding material. Reniform nematode resistant plants were of diverse cytogenetic constitution but
    individuals that modally formed 26II chromosomal configuration were identified at
    BC2F1, BC3F1, BC4F1, and BC5F1 generations. Three SSR markers, BNL3279_114,
    BNL1066_156, and BNL836_215 and one phenotypic marker, green-colored fuzz
    (Fzglon), were identified to be tightly-linked to the resistance locus. Extension of the
    association analysis and linkage estimation to 16 susceptible self progeny (BC1S1,
    BC3S1 and BC6S1) and 374 susceptible backcross hybrids (BC2F1-BC8F1) mapped the
    resistance locus to chromosome 11 of cotton with BNL3279_114 on one side and Fzglon
    on the other at 0.8 cM and 2.8 cM, respectively. Besides reniform nematode-resistance
    introgression, genome-wide introgression efforts were also conducted. Low micronaire
    and high fiber strength were the two most promising traits identified in the HLA-derived
    introgressed generations. Most of the introgressed generations had high variability for
    the fiber-quality traits than the commercial checks, thus providing more opportunities for
    selection and improvement.

publication date

  • December 2007