ASSESSMENT OF POTATO BREEDING PROGRESS IN THE USA OVER THE LAST CENTURY

Potato (Solanum tuberosum subsp. tuberosum) production has increased s ir-fold (per unit area) in the USA since the 1920s. Direct comparison of potato cultivars released during the past century can help us under stand how potato breeding has contributed to these production improvem ents and to other important traits associated with marketing and utili zation, Our objective was to study trends in potato genetic improvemen t during four subjective breeding periods (BP) (pre-1900 = BP I; 1930 to 1949 = BP II; 1950 to 1969 = BP III; 1970 to present = BP IV), and also to compare performance between and within the three major cultiva r types (round-white, long, and red-skinned), In field trials conducte d from 1990 to 1992, under best management practices (with scheduled i rrigation) in Michigan, the greatest total yield potential was observe d in several cultivars released during BP I and II. These cultivars al so had late vine maturities. On average, BP II had the greatest market able yield. Cultivars released in BP III had the lowest total yield, e arliest vine maturity, highest scab resistance and most favorable tube r appearance, General trends over periods were for earlier maturity an d improved tuber appearance. Round-white cultivars improved for chip-p rocessing ability and dry matter content over breeding periods, while long types increased in percent marketable yield only in BP IV. No tre nds were observed for scab resistance. When cultivars were grouped acc ording to tuber ape, there were no differences in total yield; however , the long types had the lowest marketable yield and the red-skinned t ypes had lowest dry matter content.