INTRODUCTION

Diploid potato clones which produce unreduced gametes merit particular attention because of their value in genetic research and in the breeding of new cultivars. There are various mechanisms that lead to the production of unreduced (2n) gametes; and these have diverse genetic consequences. The value of diploid clones and their utilization depends on the production mechanism (Mendiburu et al. 1970; Mendiburu & Peloquin 1979). Clones forming unreduced gametes via First Division Restitution (FDR) can be used in the following ways:-

1) To transfer genes from diploid species to tetraploid cultivars since they cross easily with both diploids and tetraploids (Hanneman & Peloquin 1967, 1968; Jakubiec & Suska 1981).

2) To study the inheritance of characters in the tetraploid progeny and the combining ability of the maternal parent (Jakubiec & Narkiewicz 1981), because they form homogenous gametes.

3) To transfer heterozygous blocks of alleles to the Fl progeny by crossing selected diploids with tetraploids, and thus ensuring a high level of heterosis (de Jong et al. 1981).

4) To produce Fl seeds which are genotypically uniform by utilizing the ability of clones to produce female and male unreduced gametes. This provides the opportunity of producing cultivars from true seed (TPS) (Anon 1979; Jackson, this volume).

In this paper the following are discussed:

1. 1) The characteristics of ‘NG’ clones which produce unreduced gametes.

2. 2) The fluctuation of big pollen production during the growing season.

3. […]