A plot design to sequentially harvest early generation selections and its use in evaluating fresh market characteristics of three new cultivars

A plot design was developed to compare changing yield and quality characteristics of early generation selections in our potato breeding program over a 6-wk harvest season. In this design all replicates for one harvest date are located within one row to facilitate harvesting and the variety plot arrangements in adjacent rows are identical to eliminate inter-variety plant competition effects. To illustrate the usefulness of this design, three new fresh market cultivars, Norkotah Russet, HiLite Russet, and Frontier Russet, and a standard commercial cultivar, Norgold Russet, were harvested every 10 to 14 days from late July through early September to measure earliness and optimum time of harvest for each cultivar. Each cultivar was found to have a characteristic maturation pattern. Total and marketable yields and tuber size distribution generally improved in all four cultivars as the harvest season progressed. However, the yield of marketable tubers of Norkotah and Frontier peaked and then decreased later in the season as many tubers became oversized (over 340 gms). Tuber number per plot was a stable attribute and was judged to be the most important factor determining performance of each line. Norkotah and Frontier produced fewer tubers and showed rapid tuber bulking and early production of marketable tubers of preferred sizes. HiLite produced more tubers than the other cultivars so had higher percentages of undersized tubers in late July and early August, but it produced high yields and desirable size distributions in late August and early September. Specific gravities for all three new cultivars decreased during early August, increased in mid-August as plants died, and then declined. HiLite and Frontier had higher solids than Norgold and Norkotah throughout the season.