Evaluation of four dwarfing cherry rootstocks combined with 'Kordia' and 'Regina' in the agro-environmental conditions of northwest Croatia

Assessment of the suitability of four dwarfing rootstocks (Gisela 5, Gisela 6, Piku 1 and PHL-C) for the high-density sweet cherry production was carried out in a seven-year field trial (2006-2012). 'Kordia' and 'Regina' cultivars were grafted on the four rootstocks, with the use of pollinating cultivars 'Summit', 'Skeena' and 'Duroni 3'. A spindle type of training system was used with the spacing between rows of 4 m and spacing within a row of 2.5 m. Trial was carried out at the experimental site of the Institute of Pomology (at Donja Zelina near Zagreb), on a heavy acidic soil - pseudogley, with the use of drip irrigation. The following parameters were analysed: rootstock and scion growth, rootstock-scion relation (compatibility), trunk cross sectional area (TCSA), the need for trellising, fruit yield plant^-1 and ha^-1, cumulated yield efficiency index (CYEI), impact of rootstock on bark splitting and sprouting, and the tree vigour. The experiment showed the particularities of the rootstock genotypes, e.g., the most intensive trunk growth was recorded on PHL-C, the most intensive rootstock growth and the highest number of root sprouts was recorded on PHL-C, the most pronounced incompatibility was found on Gisela 6, the bark splitting problem was detected on Piku 1, the highest cumulative yield (2008-2011) was recorded in both cultivars grafted on Gisela 6. The highest CYEI (0.83 and 0.92) was recorded in Gisela 5; Gisela 6 induced the need the trellising, while PHL-C does not need the trellising.