Quantitative trait loci for polyamine content in an RFLP-mapped potato population and their relationship to tuberization

DNA-based genetic markers are nom widely used by geneticists to locate genes for quantitative traits, and may also serve as a valuable tool for dissecting complex physiological phenomena, Van den Berg et al, (1996a QTL analysis of potato tuberization. Theor Appl Gen 93: 307-316), using restriction fragment length polymorphism (RFLP)-mapped populations of potato, detected eleven quantitative trait loci (QTLs) for tuberization. Taylor et al. (1992 Expression and sequence analysis of cDNAs induced during the early stages of tuberisation in different organs of the potato plant [Solanum tuberosum L.]. Plant Mol Biol 20: 641-651) have identified one of the gents associated with tuberization as that for the enzyme S-adenosylmethionine decarboxylase (SAMdc), an enzyme of the polyamine biosynthetic pathway. Chromosomal loci for SAMdc and arginine decarboxylase were established on the potato and tomato chromosomal maps, respectively, by hybridizing cDNA probes for these genes to RFLP digests, The polyamine content of leaves from an RFLP-mapped potato population was analyzed by fluorescence detection following HPLC, with quantitation using an internal standard. The data were analyzed by the 'qGene' statistical program, and QTLs for polyamines were detected on seven chromosomes. At least sis QTLs were found for spermine, two for spermidine, and two for putrescine. A spermidine QTL was on chromosome 5 linked to marker TG441, very close to the place where SAMdc mapped, There was some congruence between QTLs for spermine and those previously detected for tuberization and dormancy, but relationships were not consistent.