GENOTYPIC VARIATION OF ROOTSTOCKS FOR GROWTH AND PRODUCTION IN CUCUMBER - POSSIBILITIES FOR IMPROVING THE ROOT-SYSTEM BY PLANT-BREEDING

Variation for growth and production of the grafted cucumber shoot as a result of genotypic differences in the root system was analyzed for 24 cucumber accessions used as rootstock. In a first grafting experiment with five rootstocks and three scions different rootstocks led to differences in growth and production of the scion. No interaction was found between scion and rootstock effects with respect to growth and production. Further experiments involved 21 and nine rootstock accessions, respectively, and scion genotype cultivar 'Corona'. During winter cultivation the rootstocks cultivars 'Renova' and 'Esvier' significantly promoted vegetative growth of the scion and rootstock Code E induced a significantly higher fruit yield than the standard rootstock 'Corona'. During summer cultivation, rootstocks of cultivar 'Glabrous' promoted maximal vegetative growth of the scion, and rootstock Code D induced the highest fruit yield. During winter cultivation early fruit production correlated well with vegetative growth induced by the rootstock, but this correlation was almost absent during cultivation in the summer. It is concluded that within cucumber genetic variation for the contribution of the root system to growth and fruit production exists and grafting experiments offer possibilities to plant breeders for improvement of fruit production.