GENERAL COMBINING ABILITY OF TEN STRAWBERRY CULTIVARS FOR RIPENING TIME, FRUIT QUALITY AND RESISTANCE TO MAIN LEAF DISEASES UNDER POLISH CONDITIONS

The aim of the study was to estimate the combining ability of 10 strawberry cultivars (‘Camarosa’, ‘Darselect’, ‘Elsanta’, ‘Gariguette’, ‘Granda’, ‘Honeoye’, ‘Kent’, ‘Kimberly’, ‘Rosie’ and ‘Vikat’) for 6 traits in order to evaluate their usefulness in the strawberry breeding program. The progenies obtained from 45 crosses (diallel cross design, Griffing’s 4 method) were evaluated in the field experiment (randomized complete block design in 4 replicates with 15 plants per plot) located in the Pomological Orchard, Skierniewice, Central Poland. Observations across two seasons (2005 and 2006) of six traits: time of fruit ripening, marketable yield, fruit weight, fruit infection by grey mould and plant susceptibility to leaf diseases (leaf scorch caused by Diplocarpon earliana and powdery mildew caused by Sphaerotheca macularis) were recorded. Statistical analysis of data was carried out according to the fixed Griffing’s model separately for each season. In both seasons GCA and SCA effects were significantly differentiated for almost all evaluated traits (excluding fruit susceptibility to gray mould in 2006). Variation of GCA effects was predominantly larger than variation of SCA effects for all traits over both years. Late ripening cultivar ‘Vikat’ showed the highest significantly positive GCA effect for ripening time (consistent across the both seasons). Most of the other cultivars exhibited moderately negative GCA effects for this trait. ‘Granda’ and ‘Darselect’ could be promising donors for fruit size - their GCA effects for this trait were significantly positive in both seasons. ‘Kimberly’ can transmit high degree of resistance to both pathogens D. earliana and S. macularis, ‘Gariguette’ – to D. earliana and ‘Camarosa’ and ‘Kent’ – to S. macularis.