Effect of planting density and size of potato seed-minitubers on the size of the produced potato seed tubers.

Three trials were established to assess the effect of the size of seed-minitubers and their planting density, on the size of the produced tubers. The first trial was set up in 24/2/1995 in the plain of Apolonia, Thessaloniki prefecture, with cv. Spunta and the other two in 18/5/1995 in the highland plateau of Orini at Seres prefecture, with cvs Spunta and Jaerla. Four sizes of minitubers were used (<10, 10-15, 15-20 and 20-25 mm) and four planting densities (10, 20, 40 and 80 plants/m(2)). The tubers produced were classified into four size categories (<15, 15-25, 25-50 and >50 mm). This classification was not significantly different for all minituber sizes in all trials. The same also applies for the distribution of tuber weights. Over 50% of the tubers produced were concentrated in the 25-50 mm size category. The distribution of tubers by size, both as numbers and as weights, was significantly different in the various planting densities. In the size categories <15 mm and 15-25 mm the lower planting densities produced lower percentages (%) than the higher densities. In the size category 25-50 mm, where over 50% of the tubers produced were concentrated, the higher densities produced higher percentages. In the size category >50 mm the lower densities gave significantly higher percentages. It is concluded that, by increasing the planting (density the percentages of the large size tubers produced are reduced and the small-size are increased. The initial sizes of the mother seed-minitubers have no effect on the distribution of the produced tubers in sizes.