Chlorophyll fluorescence and chlorophyll content as a measure of drought tolerance in potato

Drought is considered to be one of the most serious constraints of potato production: During drought stress, the rate of photosynthesis declines as a result of decreasing intercellular CO2 concentration. Information on photosynthetic processes can be obtained from the analysis of chlorophyll fluorescence transients. In the work presented here, 12 potato cultivars differing in their drought response and representing three growth periods were subjected to drought by withholding water. Chlorophyll fluorescence was measured at weekly intervals in drought-stressed and well-watered plants. Additionally, the levels of chlorophyll a, chlorophyll b and total chlorophyll content were determined. Drought tolerance was positively correlated with chlorophyll fluorescence indicators in cultivars with a short growth period. The drought-tolerant cultivars Devlin and Aviva as well as the drought-sensitive Raritan and Vanderplank responded consistently in relation to all parameters measured. Measurements of these factors in both sensitive and tolerant, medium- and long-period growers varied, indicating no particular trends. We conclude that chlorophyll fluorescence can only be used as a measure of drought tolerance in cultivars with a short growth period. Furthermore, the levels of chlorophyll a, chlorophyll b, total chlorophyll content and the ratio of chlorophyll a and b of cultivars after four weeks without water can be used as an indication of drought tolerance.