Elmer E. Ewing Professor Emeritus, Department of Fruit and Vegetable Science 165 Plant Science, Cornell University, Ithaca, NY 14853, Telephone: (607) 255-7887

My research is focused on the physiology and genetics of potato tuberization and potato tuber dormancy. In this work I cooperate closely with Dr. P. J. Davies and Dr. I. Simko. We have been examining two backcross populations derived from dihaploid Solanum tuberosum crossed with a wild diploid potato, S. berthaultii. Dr. M. W. Bonierbale and colleagues, who made these crosses, also mapped them with RFLP markers. Our approach is to search for quantitative trait loci (QTLs) associated with tuberization and dormancy, and then to compare the QTLs with those found in the same population for various plant hormones. In cooperation with Dr. W. E. Fry and colleagues, we have taken a similar approach for examining resistance to Phytophthora infestans in the same populations.

We have shown that the ability to tuberize under long photoperiods is closely associated with early maturity; conversely, the inability to tuberize under long photoperiods is associated with late maturity. It appears that some QTLs for late maturity may coincide with QTLs for resistance to late blight, but others clearly do not overlap. Now we are in the process of testing whether any of the QTLs for maturity coincide with QTLs for hormones that have been implicated with tuberization. It is generally accepted that tuberization and maturity are controlled by a balance of hormones. Our hypothesis is that some of these hormones may also be associated with field resistance to late blight. Commonality of QTLs could help elucidate the hormonal basis for maturity differences. It could also point to particular hormones that may help explain why it is difficult to obtain good field resistance to late blight in first-early potato cultivars.

Selected Publications

Ewing, E.E., Simko, I., Smart, C.D., Bonierbale, M.W., Mizubuti, May, E.S.G., and Fry, W.E. 2000. Genetic mapping from field tests of qualitative and quanitative resistance to Phytophthora infestans in a population derived from Solanum tuberosum and Solanum berthaultii. Molecular Breeding 6:25-36.

Davies, P.. J., Simko, I. , Mueller, S.M.,Yencho, G.C., Lewis, C., McMurry, S., Taylor , M.A. and Ewing, E.E.. 1999. Quantitative trait loci for polyamine content in an RFLP-mapped potato population and their relationship to tuberization. Physiol. Plant. 106:210-218.

Vreugdenhil, D., Xu, X., Jung, C.S., van Lammeren, A.A.M., and Ewing, E.E.. 1999. Initial anatomical changes associated with tuber formation on single-node potato (Solanum tuberosum L.) cuttings: a re-evaluation. Ann. Bot. 84:675-680.

Davies, P.J., Simko, I., and Ewing, E.E. 1999. Polygene mapping as a tool for dissecting the hormonal regulation of complex plant processes. RIKEN Rev. No. 21: 55-56.

Ewing, E.E. 1997. Potato. In: The physiology of vegetable crops, ed. H.C. Wien. pp. 295-344. CAB International, Wallingford, U.K.

Šimko, I., McMurry, S., Yang, H. M., Manschot, A., Davies, P.J., and Ewing, E.E.. 1997. Evidence from polygene mapping for a causal relationship between potato tuber dormancy and abscisic acid content. Plant Physiol. 115:1453-1459.