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.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2579 |
| Date | 15 May 2009 |
| Creators | Dighe, Nilesh Deoram |
| Contributors | Stelly, David M. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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