Participating Faculty
Richard Knowles

Scientist
Department of Horticulture & Landscape Architecture
Washington State University
Pullman, WA 99164-6414

Ph.D., 1983
Washington State University

Phone: 509-335-3451
Fax: 509-335-8690
Email: rknowles@wsu.edu

 

Research Interests:
Characterizing the physiological and biochemical changes that lead to deterioration of post harvest quality in fruit and vegetable crops

Research Summary:
From a broad perspective, my research focuses on characterizing the physiological and biochemical changes that lead to deterioration of post harvest quality in fruit and vegetable crops. We currently have a major research interest in understanding the metabolic processes that contribute to physiological aging of potato seed-tubers.
Many plants are propagated through naturally adapted, vegetative structures such as tubers, rhizomes, bulbs, corms, and roots. Like true seed, vegetative propagules are often 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 that are associated with and that mediate a loss in vigor and growth potential during aging. Potato seed-tubers are ideally suited for these studies because tubers are vegetative propagules, they retain viability in cold storage for about three years, and they display significant age-induced changes in growth potential. In general, there is an ‘optimum’ tuber age where growth vigor is maximum, before which vigor increases as tubers emerge from dormancy and after which vigor decreases as tubers advance in age and eventually lose viability. Ongoing studies in this area include: the role of oxidative processes and associated defense mechanisms in the aging process; relating age-induced differences in energy metabolism during sprouting to loss of vigor; assessing the role and mechanism of phospholipid and fatty acid catabolism, relative to a gradual loss in membrane function that occurs during tuber aging; understanding the role of NADPH oxidase in the age-induced loss of hypersensitive response and wound-healing ability of tubers; and characterizing the mechanisms by which proteins become targeted for proteolysis during tuber aging.
Applied research entails studies on controlled seed-tuber aging as a technique to enhance yield and quality of potatoes, identification of biochemical markers of potato seed-tuber productivity, development of natural sprout inhibitors for use by the potato industry, storage management to preserve processing quality in potatoes, and potato variety development and testing. My program runs the postharvest evaluations of clones and cultivars in the Northwest Tri-State and Regional Potato Variety Program. We thus have access to a wide array of potato genotypes with differential susceptibility/resistance to major fungal/bacterial diseases, insect pests, cold tolerance, etc. Ideal opportunities exist to use clonal accessions from this program for basic research on the metabolic bases of resistance/susceptibility to various biotic and abiotic stresses.

Representative Publications:
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 (in press)

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. (in press).

Love, S.L., R. Novy, J. Whitworth, D.L. Corsini, J.J. Pavek, A.R. Mosley, M.J. Pavek, N.R. Knowles, C.R. Brown, S.R. James and D.C. Hane. 2005. GemStar Russet: A new russet potato variety with high yield, good culinary quality, excellent fresh market appearance, and resistance to common scab. American Journal of Potato Research (in press).

Knowles, N.R., L.O. Knowles and M.M. Haines. 2005. 1,4-Dimethylnapthalene treatment of seed potatoes affects tuber size distribution. Am. J. Pot. Res. 82:179-190.

Ozga, J.A., D.M. Reinecke and N.R. Knowles. 2004. Characterization of the loss of seedling vigor in pea (Pisum sativum L.). Canadian Journal of Plant Science 84:443-451.

Blenis, P.V., P.S. Chow, I. Duncan and N.R. Knowles. 2004. Cyanide levels near fairy rings affect the growth of grasses and fungi. Canadian Journal of Botany 82:1324-1329.

Kumar, G.N.M. and N.R. Knowles. 2003. Wound-induced superoxide production and PAL activity decline with potato tuber age and wound healing ability. Physiologia Plantarum 117:108-117.

Zabrouskov ,V. and N.R. Knowles. 2002. Lipid metabolism during aging of high a-linolenate-phenotype potato tubers. Archives of Biochemistry and Biophysics 402:136-148.

Zabrouskov ,V. and N.R. Knowles. 2002. Changes in lipid molecular species and sterols of microsomal membranes during aging of potato (Solanum tuberosum L.) seed-tubers. Lipids 37(3):309-315.

Kumar, G.N.M., R.L. Houtz and N.R. Knowles. 1999. Age-induced protein modifications and increased proteolysis in potato seed-tubers. Plant Physiology 119:89-100