Chlorophyll fluorescence as a diagnostic tool for abiotic stress tolerance in wild and cultivated strawberry species

Chlorophyll (Chl) fluorescence analysis was used to assess stress tolerance in wild and cultivated strawberry species. We found that the parameters, photochemical quenching (1-qP), non-photochemical quenching (qN), and maximum quantum yield (Fv/Fm), can serve as stress indicators because they are sensitive to early responses to stress. The most sensitive region used for measuring Chl fluorescence in strawberry leaves was the upper surfaces of leaflets located in the middle of new leaves. An analysis of the Chl fluorescence characteristics of strawberry species showed that octoploid species had greater stress tolerance than diploid species. The 'Whiteberry' maintained high levels of 1-qP and qN through the dissipation of excess excitation energy as heat during early stress treatment. These results suggest that 'Whiteberry' has a photoinhibition system that allows it to respond to stress in a more sensitive manner than other cultivars. Therefore, among the Chl fluorescence parameters examined, 1-qP and qN, can serve as good indicators for comparing stress tolerance, and they can be used to simultaneously screen many plants for stress tolerance in strawberry breeding programs.