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Previous studies revealed difficulties in retention and recombination of alien species germplasm by conventional introgression in upland cotton (Gossypium hirsutum L.) due to incompatibility at the whole-genome level. An alternative approach is to use alien species chromosome substitution (CS) lines, whereby retention and recombination can be differentially increased for a specific chromosome or chromosome segment. Here we report for the first time on the development of a set of CS lines from two alien species in a common genetic background of upland cotton. The overall objective of this research is to report on the chromosomal association of important fiber traits using a partial-diallel mating design among CS lines of G. tomentosum Nutt. Ex Seem (CS-T), a wild tetraploid species endemic to Hawaii, G. barbadense L. (CS-B), a cultivated tetraploid species with improved fiber quality traits, and 'TM-1' (G. hirsutum), the recurrent parent with improved agronomic traits and moderate fiber quality traits. The genetic effects associated with CS lines were dissected into additive, homozygous dominance, and heterozygous dominance genetic effects using an additive-dominance statistical model. Five of six CS-B lines and two of six CS-T lines had significant additive genetic effects on lint percentage, indicating that the respective substituted alien chromosome carried alien alleles with potential to improve lint percentage in upland cotton. Fifty-six percent of 16 different significant additive effects associated with the CS-B lines could be useful to improve fiber traits in TM-1. On the contrary, 40% of 15 significant additive genetic effects of the CS-T lines had potential to improve fiber traits. Results suggested that CS lines can unveil many beneficial alleles harbored cryptically in the other AD-genome species and render them more accessible for research and cotton genetic improvement. [ABSTRACT FROM AUTHOR]

Chromosome substitution lines (CSLs) have been developed for selected chromosomes from two tetraploid species of Gossypium and are effective ways to target introgression of alleles from exotic tetraploid species into Upland cotton (G. hirsutum L.) Genetic effects of chromosomes 1, 4, and 18 from Upland cot- ton (TM-1), Pima cotton (G. barbadense L.), and Hawaiian cotton (G. tomentosum Nutt. ex Seem) were estimated by topcrossing TM-1 and six isochromosomal CSLs with fve upland cultivars and comparing F2 and F3 hybrids for agronomic and fiber traits. Data were analyzed according to an additive-dominance (AD) model. Additive genetic effects were greater than dominance effects for lint percentage, fiber uniformity, fiber strength, and elongation; whereas, dominance effects were greater than additive effects for boll weight, lint yield, fiber length, and fiber micronaire. All additive x environment effects were small. Dominance x environment effects were only significant for boll weight, lint yield, and fiber micronaire. Chromosome B04 and B18 from Pima cotton and T01 from Hawaiian cotton had significantly greater additive effects for lint percentage than homologs. Chromosomes 1, 4, and 18 from the three species generally showed negative additive effect on lint yield compared with cultivars. Chromosome 1 from Hawaiian cotton had greater additive effects on fiber length than homologs. Chromosomes 1 and 4 from Pima cotton showed greater additive effects on fiber strength than homologs. The magnitude of additive effects on important agronomic and fiber traits show that Pima cotton and Hawaiian cotton harbor useful alleles for Upland cotton breeding programs. [ABSTRACT FROM AUTHOR]