Marker-assisted characterization of durum wheat Langdon-Golden Ball disomic substitution lines

The durum wheat cultivar 'Golden Ball' (GB) is a source of resistance to wheat sawfly due to its superior solid stem. In the late 1980s, Dr. Leonard Joppa developed a complete set of 14 'Langdon' (LDN)-GB disomic substitution (DS) lines by using GB as the chromosome donor and LDN as the recipient. However, these substitution lines have not been previously characterized and reported in the literature. The objectives of this study were to confirm the authenticity of the substituted chromosomes and to analyze the genetic background of the 14 LDN-GB DS lines with the aid of molecular markers, and to further use the substitution lines for chromosomal localization of DNA markers and genes conferring the superior stem solidness in GB. Results from simple sequence repeat marker analysis validated the authenticity of the substituted chromosomes in 14 LDN-GB DS lines. Genome-wide scans using the target region amplification polymorphism (TRAP) marker system produced a total of 359 polymorphic fragments that were used to compare the genetic background of substitution lines with that of LDN. Among the polymorphic TRAP markers, 134 (37.3%) and 185 (51.5%) were present in LDN and GB, respectively, with only 10 (2.8%) derived from Chinese Spring. Therefore, marker analysis demonstrated that each LDN-GB DS line had a pair of chromosomes from GB with a genetic background similar to that of LDN. Of the TRAP markers generated in this study, 200 were successfully assigned to specific chromosomes based on their presence or absence in the corresponding LDN-GB DS lines. Also, evaluation of stem solidness in the substitution lines verified the presence of a major gene for stem solidness in chromosome 3B. Results from this research provides useful information for the utilization of GB and LDN-GB DS lines for genetic and genomic studies in tetraploid wheat and for the improvement of stem solidness in both durum and bread wheat.