Submitted to: Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/1/2005
Publication Date: 3/1/2006
Citation: Saha, S., Jenkins, J.N., Wu, J., McCarty Jr., J.C., Gutierrez, O.A., Percy, R.G., Cantrell, R.G., Stelly, D.M. 2006. Effects of chromosome-specific introgression in upland cotton on fiber and agronomic traits. Genetics. 172:1927-1938. Interpretive Summary: The breeder frequently faces many challenges in the process of introgressing G. barbadense genes into Upland cotton. The utilization of backcrossed chromosome or chromosome arm substitution lines as the donor parent will help to overcome the problems of interspecific incompatibility at the whole genome level while targeting fiber traits for Upland cotton improvement. In this research 14 different euploid (2n = 52) backcrossed substitution lines (CS-B) for different chromosome and chromosome arms of 3-79 (G. barbadense) were crossed with TM-1 (G. hirsutum) to develop chromosome-specific hybrids (F1) and subsequently by selfing to produce a chromosome-specific F2 population. These lines resulting from this manipulation are genetically identical except that each differs by the recombination of a specific homologous pair of chromosomes from 3-79 and TM-1. Observation and measurement of different quantitative traits in such a uniform genetic background will detect the effect of the group of genes that a specific chromosome carries. The overall goal of this research is to identify the chromosomal association of some important agronomic and fiber traits. Differences in additive and dominance effects were observed among the various CS-B lines for several of the traits measured. Results demonstrated that some of the CS-B lines may be useful for improving germplasm of Upland cotton.
Technical Abstract: Interspecific chromosome substitution is among the most powerful means of introgression and steps toward quantitative trait locus (QTL) identification. By reducing the phenotypic "noise" from other chromosomes, it greatly empowers the detection of genetic effects by specific chromosomes on quantitative traits. These advantages of chromosome-specific analysis can be extended to derived populations. Here, we report on such results for 14 cotton lines (Gossypium hirsutum L.) with specific chromosomes or chromosome arms from G. barbadense L. substituted into G. hirsutum (CS-B), and F2 families derived from CS-B lines crossed with the recurrent parent, G. hirsutum TM-1. Data on boll size, lint percentage, micronaire, 2.5% span length, elongation, strength and yield were generated by replicated field experiments in five diverse environments, and analyzed under an additive dominance (AD) genetic model. Additive effects were significant for all traits and dominance effects were significant for all traits except 2.5% span length. However, differences in additive and dominance effects were observed among the various CS-B lines for several of the traits measured. CS-B25 had additive effects increasing fiber strength and fiber length and decreasing micronaire. CS-B16 and CS-B18 had additive effects related to reduced yields. Heterozygous and homozygous dominance effects varied among the different CS-B lines relative to TM-1. For some CS-B lines, the heterozygous dominance effects differed from the homozygous dominance effects. The results point toward specific chromosomes of G. barbadense 3-79 as the probable locations of the genes significantly affecting quantitative traits of importance. To complement this work, CS-B lines intermatings will be used to define interchromosomal inter-locus interactions; and chromosome-specific RIL's will be developed to empower the QTL definition process with both high sensitivity and high resolution.