Photochemical quenching of chlorophyll fluorescence and drought tolerance in different durum wheat (Triticum durum) cultivars

Abstract

SUMMARYThe aim of this study was to identify a fluorescence parameter whose estimate could be used reliably for a drought tolerance test in durum wheat (Triticum durum). Twenty-five cultivars were grown in a glasshouse over two seasons (1987/88 and 1988/89) at Foggia, Southern Italy. Photochemical and non-photochemical quenching (qQ and qE), the half time of fluorescence decay (tP½) and the initial slope of fluorescence decay (ISPS) were measured on control and dehydrated pre-darkened excised leaves; qQ and qE were measured twice: first at 14 s after actinic illumination and second at the steady state.No great difference in qQ and qE was apparent between control and dehydrated leaves at the steady state; however, at 14 s after illumination there was a decrease in qQ and in ISPS and an increase in tP½ in dehydrated leaves. The predictive capability of fluorescence parameters was assessed by comparison with a yield-based drought susceptibility index (DSI). The percentage decrease in qQ at 14 s showed the highest correlation with DSI (r = 0·75, significant at P < 0·001), so it may be considered a good indicator of drought tolerance in durum wheat. Results obtained at different developmental stages with different fluorescence levels (Fo, P and Fm) and parameters (qQ, qE and tP½) indicated that for maximum reliability the test must be applied at the vegetative phase.