Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/24/2006
Publication Date: 4/24/2006
Citation: Vega, S.E., Bamberg, J.B., Palta, J.P. 2006. Gibberellin-deficient dwarfs in potato vary in exogenous GA3 response when the GA1 alelle is in different genetic backgrounds. American Journal of Potato Research. 83:357-363. Interpretive Summary: Potato is the most important US vegetable, and one of the best hopes for feeding an increasingly hungry world. Breeders need to keep producing better varieties to meet changing needs of the industry and preferences of consumers. Breeders get raw materials from genebanks, so it is in the interest of US Agriculture for the US Potato Genebank at Sturgeon Bay, Wisconsin to discover and characterize new genes that are in the genebank. One such trait is a genetic mutation that results in a deficiency of gibberellin (GA), a hormone, in the plant. Since GA strongly affects many important physiological processes like sprouting, starch accumulation, and tuberization, a mutant that is deficient can be a very valuable tool for studying how GA works in potato plants. When various individual mutants were grown in a highly controlled test tube environment and GA was precisely applied, we found slight differences in the timing, type of growth and degree of response. This shows that if this mutant is used for a test of GA response, one highly responsive genotype should be selected and multiplied for uniform results. The variation among mutant genotypes might also be used to identify and characterize other genes that interact with GA physiology in potato. These kinds of results improve our understanding of the role of a major hormone in potato, and, ultimately, how its physiology can be manipulated to produce a better potato crop.
Technical Abstract: In potatoes, gibberellins are involved in such important processes as seed germination, flowering, maturation, tuber dormancy and tuberization. GA-deficient mutants lack the ability to produce adequate amounts of gibberellin for normal growth, resulting in a rosette type growth and very short internodes. Diploid and tetraploid ga1 mutants were obtained by crossing the S. andigena carriers with S. chacoense and other tetraploid wild potato species. Mutants were grown on MS media containing different levels of gibberellin (GA3). Plant height and visual observations were made as a way to assess the response of these mutants to GA3. Normal growth was restored in most of the mutants when concentrations between 0.8 and 1.2 'M GA3 were used. Significant differences in sensitivity were noted in terms of GA3 requirements, time of response, type of growth (i.e. variation in translocation was evident by the failure of internode elongation in the apical area of some genotypes). The ga1 dwarf mutant may be subject to modifier genes or could even be conferred by a series of isoalleles. These results indicate that bioassays would be best conducted on one clonally-replicated genotype selected for maximum GA response. The variation among genotypes documented here also points out the opportunity to identify and characterize modifier genes that likely represent physiological processes that interact with the GA response in these mutants.