Effect of propagule type and growing environment on antioxidant activity and total phenolic content in potato germplasm

Wild potato species are maintained primarily as botanical seed populations, so tuber trait studies require conversion of germplasm to tuber form. Such tubers may be obtained from seedlings produced directly from botanical seed or from plants grown from tuber propagules (tuberlings). Since most wild species require short days for tuberization, it is not possible to generate field tubers of these species in most USA locations. Historically, tubers for research evaluations have been generated in the artificial conditions of the winter greenhouse. Since the potato crop is normally grown from tubers produced from tuberlings grown in the field, it is important to know how much results differ when evaluating tubers that were produced from seedlings grown in the greenhouse. We compared antioxidant activity and phenolic content of tubers generated in the greenhouse at Sturgeon Bay, WI, from seedlings, and tubers generated from both seedlings and tuberlings in the field at the Kula Experiment Station, Kula, Maui, HI. A ‘mini-core’ set of 75 PIs representing 25 wild and primitive cultivated species was used. Differences in means of propagule types and growing environments were significant but not large. Average amount of antioxidant activity and phenolic content of tubers from field-grown seedlings was higher than that of tubers from tuberlings. These values were also higher in field-grown tubers than in greenhouse-grown tubers. Relative performance was similar regardless of environment or propagule type, with some important exceptions. Tubers of Solarium pinnatisectum and Solanum jamesii were high regardless of treatment. In contrast, tubers of certain Solanum microdontum, canasense, stenotomum and commersonii (species much more amenable to breeding) exhibited high antioxidant levels when produced in the field from tuberlings, but not when produced from greenhouse-grown seedlings. Thus, some germplasm may not exhibit useful antioxidant potential when tubers are produced in artificial greenhouse conditions.