CHLOROPHYLL A FLUORESCENCE: A FAST AND LOW-COST TOOL TO DETECT SUPERFICIAL SCALD IN 'ROCHA' PEAR (PYRUS COMMUNIS L. 'ROCHA')?
This study aimed to test whether the chlorophyll a (Chla) fluorescence determined by a low-cost non-modulated fluorometer could provide fast, reliable and non-invasive estimators of superficial scald in ´Rocha pear (Pyrus communis L. Rocha). Fruit were harvested before the optimal maturation stage and cold stored under normal atmosphere for 7 months (NA: 0°C, 90-95% RH) and 2 in controlled atmosphere (CA: 0°C, 90-95% RH, 1.5 kPaO2 + 0.5 kPa CO2) (T), or harvested at the optimal maturation stage and cold stored for 9 months under CA (C). Then, they were transferred to shelf-life conditions (22±2°C, 70% RH) and followed for 7 d. Chla fluorescence, scald index (SI), ripening attributes, α-farnesene, conjugated trienols, and photosynthetic pigments were determined for each pear in both groups. Conditions chosen before shelf-life did not prevent the subsequent ripening of any fruit, but changed dramatically the superficial scald development pattern: in C fruit, the disorder developed progressively during shelf-life, whereas in T fruit, it peaked during storage. C fruit exhibited a significant negative correlation (R=-0.65; p<0.05) between Fv/Fm and scald development, but not with ripening (R=-0.15; p<0.05). As expected, the opposite was observed in T fruit, in which only a low, positive, yet significant correlation was found between Fv/Fm and ripening (R=0.44; p<0.05). The multiple regression approach using Fv/Fm and other Chla fluorescence parameters produced an equation from which we calculated the predicted scald index in C fruit. This correlated clearly (R=0.73; p<0.05) with the real values visually assessed. If color values a*, b* and °Hue were included in this multiple regression, the correlation was significantly enhanced (0.91; p<0.05). Although preliminary, this study has shown that basic Chla fluorescence parameters are valuable estimators of superficial scald in Rocha pear and might be used in the early detection of the disorder.
Gardé, I., Antunes, M.D., Marques da Silva, J., Guerra, R. and Cavaco, A.M. (2012). CHLOROPHYLL A FLUORESCENCE: A FAST AND LOW-COST TOOL TO DETECT SUPERFICIAL SCALD IN 'ROCHA' PEAR (PYRUS COMMUNIS L. 'ROCHA')?. Acta Hortic. 934, 159-166
diagnosis, fruit photosynthesis, photosynthetic pigments, disorder