Abstract
The genetic variability of two allotetraploid cultivated cotton species, Gossypium barbadense and G. hirsutum was analyzed for restriction fragment length polymorphisms (RFLPs). The analysis was made on G. barbadense cv. Pima S6, G. hirsutum cv. Coker 201, SP37 (G. hirsutum introgressed with G. barbadense), and the nearly isogenic lines of G. hirsutum AcB2, AcB3, and AcB7 to examine DNA sequence divergence and to identify DNA markers linked to the B2, B3, and B7 genes controlling bacterial blight resistance. A PstI genomic library containing 0.4-5 kb fragments of G. barbadense cv. Pima S6 nuclear DNA was constructed. Nuclear DNAs from six cultivars were compared with two restriction enzymes, EcoRI and BamHI. One hundred and forty random clones from a PstI genomic library were used as probes to screen for RFLP variation within G. barbadense and G. hirsutum cultivars. Screening such a large number of clones was facilitated by co-labeling and simultaneous probing of sets of up to ten random genomic clones. Although restriction patterns of nuclear DNA from six cultivars displayed considerable overall similarity, nine molecular changes were detected. Based on RFLP data, pCL2-34 may be a clone linked to B2, which is a major gene for bacterial blight resistance. Therefore, pCL2-34 may be used as a DNA marker linked to quantitative trait loci (QTL) controlling bacterial blight resistance, thus allowing selection of this economically important trait in cotton germplasm. In addition, two clones, pCL1-36 and pCL1-69 revealed distinct nuclear DNA profiles in Pima S6 and SP37. Although pCL1-36 and pCL1-69 do not appear to be linked to any specific genes (B3, B7 genes), they might be a potential source of DNA markers useful for distinguishing G. barbadense cv. Pima S6 and SP37 (blight resistant var.) from other G. hirsutum cultivars (blight sensitive var.). Rates of sequence divergence between G. barbadense and G. hirsutum are relatively low. Based on the results of digests with enzymes recognizing hexanucleotide sites (EcoRI and BamHI) and hybridization analysis with 140 probes, the genetic difference between Gossypium barbadense and G. hirsutum is about 0.27% at the nucleotide level.
Kwon, In Sook (1991). Restriction fragment length polymorphism in Gossypium barbadense and G. hirsutum. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1277036.