INTRODUCTION

In the Netherlands most potato breeders grow seedlings in the glasshouse in pots. The heaviest tuber per plant is harvested as seed for the first clonal generation. The seed tubers are small and moreover weight varies enormously within populations. As seed tuber weight affects the phenotype of the first year clones, the variation in weight has a negative effect on selection efficiency. This has been confirmed by the results of Blomquist and Lauer (1962), Swiezynski (1968), Brown et al. (1984) and Maris (pers. comm.). These workers all found that plants obtained from heavier seed tubers had better chances in plant selection but none could specify a weight interval at which tuber weight plays a less decisive role in the selection of first year clones.

Research on this selection problem will be presented in this paper.

MATERIALS AND METHODS

The influence of weight of seed tubers on the phenotype of first year clones is being studied in two similar 2-year experiments. Experiment 1 started in 1984 and ended in 1985 whilst experiment 2 started in 1985 and will be concluded in 1986. During the first experimental year, first year clones were grown in the field. Each genotype was represented by six plants (experiment 1) and eight plants (experiment 2), obtained from tubers differing in weight. For experiment 1 tuber weight ranged between 1.6–80.3 g and for experiment 2 between 1.5–77.5 g.