Study of complex biochemical pathway and genes involved in cotton fiber development is important to understanding the biology behind the longest plant cell known. Cotton seed epidermal cells go through initiation, elongation, secondary cell wall synthesis and maturation to become long lint fibers. Natural and artificial mutants are excellent tools to help decipher functions of genes involve in fiber development and/or a source to make improved germplasm. Here we used a natural mutant, Ligon lintless-2 (Li2), to identify gene/s in the fiber elongation process. In another experiment, we used mutant lines developed through EMS-mutagenesis to improve fiber quality of elite germplasm and study the effect of pyramiding novel alleles conferring improved fiber quality. A population of 1,545 F2 plants derived from a cross between Pima S-7 (G. barbadense) and an Li2 mutant line (G. hirsutum) and 144 DNA markers were used to fine map the Li2 region on chromosome 18. We identified terminal deletion of the long arm of chromosome 18 to be the probable cause of the Li2 phenotype, identifying seven candidate genes. By Virus­ Induced Gene Silencing (VIGS), knockdown of two genes, GhUGT87A1-D1a and GhUGT87 A, showed Li2 like phenotypes. This research provides new insight into the causal mutation of the Li2 phenotype and identifies genes involved in fiber elongation. A total of 12 mutant lines showing striking improvement in fiber attributes were studied for the stability of the mutant phenotype, heritability of the improved trait and interaction between novel alleles. A total of ten populations were developed, four involving crosses between TAM94L25 mutant lines and GA230, four from ACALA1517-99 mutant lines X GA230 and two from ACALA1517-99 mutant lines x TAM94L25 mutant lines. Each population had either a combination of two mutant lines in GA230 background or a combination of four mutant lines (ACALA1517-99 mutant lines x TAM94L25 mutant lines). Based on replicated trials in three environments we concluded that most mutant lines can be used to improve elite germplasm and thus mitigate the genetic bottleneck in cotton. In most instances, combining different mutant lines made it possible to improve two fiber attributes in a single cross.