Molecular and physiological responses to drought stress in Fragaria sp.

Drought stress and its effects on crop productivity in horticultural systems are receiving increasing interest. Strawberry cultivation relies on irrigation and is sensitive to even a short period of water deficit. The main objectives of this study were to identify and characterize the plant defense mechanisms to drought stress in Fragaria and to classify available genotypes based on their drought tolerance capacity. Chlorophyll fluorescence proved to be a useful non-destructive technique to detect drought stress in strawberry. The osmotic adjustment by sugars and poline as well as anti-oxidative response was involved in plant response to drought stress. Candidate genes that might be involved in plant response to water deficit were cloned and isolated from Fragaria. EST markers were developed from these candidate genes and applied together with AFLP markers for a marker-trait association analysis for drought tolerance in Fragaria. EST markers associated to drought tolerance in Fragaria were identified. The differential expression level of Fragaria homologous sequences (candidate genes) was also analyzed in a selected set of four Fragaria genotypes under different stages of water deficit. Overall, results confirmed the involvement of carbohydrate metabolism in osmotic adjustment, of antioxidant ROS scavenging defense system and of ABA- dependent and -independent signalling pathways in Fragaria adaptive response to water deficit. Finally, a gene silencing (RNAi)/over expression approach was applied for further functional analysis under drought stress.