Phenological and physiological responses to drought stress and subsequent rehydration cycles in two raspberry cultivars

- Heritage and Meeker raspberry plants showed different phenological responses to drought stress.
- Differential physiological responses were observed in Heritage and Meeker plants under drought stress.
- Proline and soluble total sugars increased with drought stress in Heritage and Meeker varieties.

Raspberry (Rubus idaeus L.) is a deciduous plant with perennial roots, 75% of which are concentrated in the upper level of the soil. Its shallow rooting system requires a regular water supply; a water deficit can affect fructification as well as cane growth and yield for the following season. Despite the demonstrated drought stress impact on the raspberry, there is little information about the phenological and physiological responses to drought stress. The main goal of this study was to evaluate the effects of drought stress on the phenological phases, physiological parameters and yield of two raspberry cultivars: Heritage (remontant type) and Meeker (non-remontant type). All plants were grown in pots under greenhouse conditions, and the following watering treatments were applied: (T1) well-watered, 100% irrigation and (T2) a controlled drought-stress cycle. The volumetric soil water content (θ), phenological phases, leaf net photosynthetic rate (A), transpiration rate (T), and stomatal conductance (gs) were registered periodically. The free proline and total soluble sugars were also determined. Based on the phenological study, Heritage under drought-stress (T2) showed earlier flowering and a shorter fruit production period in relation to well-watered plants (T1). In Meeker, T2 extended the cane and summer lateral elongation, showing earlier senescence. Leaf gas exchange decreased with drought stress, A declined after 28-day period under drought stress, from 9.2 μmolCO2 m−2 s−1 to 3.0 μmolCO2 m−2 s−1 in Heritage, and from 12.2 μmolCO2 m−2 s−1 to 3.0 μmolCO2 m−2 s−1 in Meeker. In both cultivars, the free proline and total soluble sugars increased with drought stress. The fruit production was also affected in the next season under T2 condition, decreasing in 34 and 38% in relation to well-watered plants.