Department of Horticulture & Landscape Architecture. Professor/Horticulturist. Ph.D. 1983, Washington State University.
Physiological and biochemical changes that mediate loss of post harvest quality in fruit and vegetable crops are of interest. We currently have a major research focus on physiological aging of potato seed-tubers. Potatoes are propagated vegetatively from virus-free seed-tubers stored prior to planting. Storage conditions can influence the rate of aging, which subsequently affects plant growth and crop yield.
Using potato as a model, we are investigating metabolic changes associated with loss of vigor and growth potential during aging. Ongoing studies include: oxidative processes and associated defense mechanisms in the aging process; age-induced changes in energy metabolism during sprouting; mechanism of phospholipid and fatty acid catabolism relative to deterioration in membrane function during aging; role of NADPH oxidase in the age-induced loss of hypersensitive response and wound-healing ability of tubers; and mechanisms by which proteins become targeted for proteolysis during tuber aging.
Applied research includes techniques to manipulate apical dominance of seed-tubers to optimize tuber set and size development in relation to market requirements, biochemical/molecular markers of apical dominance and yield potential in seed-tubers, discovery and development of sprout inhibitors, in-season stresses affecting storability and postharvest quality, storage management techniques to preserve processing quality, and potato variety development.
My program evaluates the storability, processing quality, and culinary attributes of clones and cultivars in The Pacific Northwest Potato Variety Development Program (WA, ID, OR). We thus have access to potato genotypes with differential susceptibility/resistance to major pathogens, insects, cold/heat tolerance, drought, etc. The germplasm from this program offers a unique opportunity for fundamental research on the metabolic bases of resistance/susceptibility to various biotic and abiotic stresses in potato.
Novy, R.G., J.L. Whitworth, J.C. Stark, B.A. Charlton, S. Yilma, N.R. Knowles, M.J. Pavek, et al. 2012. Palisade Russet: A late blight resistant potato cultivar. Am. J. Pot. Res. 89: 89-101.
Weeda, S.M., Kumar, G.N.M. and N.R. Knowles. 2011. Protein mobilization from potato tubers during long-term storage and daughter tuber formation. Int’l. J. Plant Sci. 172: 459-470.
Kumar, G.N.M., Lulai, E.C., Suttle, J.C. and N.R. Knowles. 2010. Age-induced loss of wound-healing ability in potato tubers is partly regulated by ABA. Planta 232: 1433-1445.
Weeda, S.M., Kumar, G.N.M. and N.R. Knowles. 2010. Correlative changes in proteases and protease inhibitors during mobilization of protein from potato (Solanum tuberosum L.) seed-tubers. Functional Plant Biology 37: 32-42.
Nissen, M., Youn, B., Knowles, D.B., Ballinger, J.W., Lam, K.S., Kumar, G.N.M., Knowles, N.R., and ChulHee Kang. 2009. Characterization of potato multicystatin and its structural comparison with other cystatins. Plant Cell 21: 861-875.
Knowles, N.R., Driskill E.P. Jr., and L.O. Knowles. 2009. Sweetening responses of potato tubers of different maturity to conventional and non-conventional storage temperature regimes. Postharvest Biol. Tech. 52: 49-61 http://dx.doi.org/10.1016/j.postharvbio.2008.08.015.
Kumar, G.N.M., Suresh Iyer and N.R. Knowles. 2007. Extraction of RNA from fresh, frozen, and lyophilized tuber and root tissues. J. Agric. Food Chem 55:1674-1678.
Knowles, N.R. and E.S. Plissey. 2007. Maintaining tuber health during harvest storage, and post-storage handling. In Potato Health Management, D. Johnson ed., 2nd edition, APS Press (invited chapter) (in press).
Driskill, E.P. Jr., L.O. Knowles, and N. R. Knowles. 2007. Temperature-induced changes in potato processing quality during storage are modulated by tuber maturity. Am. J. Pot. Res. (in press).
Grunenfelder, L., L.O. Knowles, L.K. Hiller and N.R. Knowles. 2006. Glycoalkaloid development during greening of fresh market potatoes (Solanum tuberosum L.). J. Agric. Food Chem 54:5847-5854.
Knowles, N.R. and L.O. Knowles. 2006. Manipulating stem number, tuber set, and yield relationships for northern- and southern-grown potato seed lots. Crop Science 46:284-296.
Novy, R.G., S.L. Love, D.L. Corsini, J.J. Pavek, J. Whitworth, A.R. Mosley, S.R. James, D.C. Hane, C.C. Shock, K.A. Rykbost, C.R. Brown, R.E. Thornton, N.R. Knowles, M. Pavek, N. Olsen, and D.A. Inglis. 2006. Defender: A high-yielding, processing potato cultivar with foliar and tuber resistance to late blight. Am. J. Pot. Res. 83:9-19.