Vegetative Growth and Flowering of Primocane Raspberry ‘Ariadne’ as Affected by Prohexadione–calcium Treatments

Abstract

Maintaining an appropriate balance between vegetative and generative growth is a prerequisite for profitable raspberry (Rubus idaeus L.) production. The objective of our study was to test the effect of prohexadione–calcium (ProCa) on vegetative growth and flowering of primocane fruiting red raspberry ‘Ariadne’ in greenhouse conditions. ProCa was applied either once or twice in a concentration of 100 ppm or 200 ppm. Double applications of ProCa reduced cane height by 33 cm (100 ppm) or by 46 cm (200 ppm). Growth reduction was the result of shortening of the internodes, because total node number in plants was unaffected. Furthermore, cane diameter was reduced in plants treated with 200 ppm ProCa. ProCa treatments reduced the total aboveground dry weight by 32% to 55% but did not affect the allocation of dry weight into different plant parts. All ProCa treatments reduced the number of flowers by 22% to 42%. In conclusion, ProCa proved effective in controlling vegetative growth of red raspberry. However, because the number of flowers was reduced, ProCa cannot be recommended for growth regulation of primocane fruiting raspberry without further studies.