Every year between 50 and 60 parent varieties and breeding lines are selected to carry out crosses. Seeds are sown or conserved under proper conditions. At present, 500.000 seeds are available in APPACALE's seed bank.

Between 25000 and 30000 seeds are sown every year. Each plant is transferred to pots and grown in a greenhouse. One tuber per plant is harvested which will be planted the next year. In total about 15000 and 20000 individuals are established.

The first years of selection are carried out in The Valle de Valdelucio, a seed production area placed in the north of Burgos ( Spain ) where the pressure of aphids is quite low so PVY infection can be under control.

The first year one tuber per clone is planted and about a 5% of them are selected. The next year 5 tubers per selected clone are grown and this process is repeated the following years, increasing the number of tubers planted per selected clone. Moreover, healthiness of the trials is controlled, especially for PVY by extensive immunological virus tests (ELISA) because it may become a serious problem in Spain .

The advanced lines, selected after several years, are grown in different localities to have a more accurate evaluation of their maturity, yield and quality features. Therefore, in the fourth year of selection the best breeding materials are evaluated in La Rioja , Castilla y León and Galicia (regions of Spain ) during two years. The best ones will be part of the official field trials carried out by the Ministry of Agriculture during two years. At least 10 years are needed to obtain a new variety.

One of the objectives of the breeding program is obtaining PVY immune clones. The clones carrying Ry genes that confers PVY inmunity or genes that confer resistance to Globodera rostochiensis and G. pallida are selected.