Evaluation of chilling sensitivity in different rice varieties. Relationship between screening procedures applied during germination and vegetative growth

Rice varieties were screened for chilling tolerance during germination and vegetative growth using different techniques. The effects of temperature during germination were investigated from 10 to 25 degrees C. The screening was most effective at 10 degrees C. Time of data collection has to be considered in order to discriminate slow germinating from chilling sensitive varieties. Chilling survival tests (10 degrees C) applied at the 2-leaf stage revealed that different chilling durations brought complementary results: the longer treatments allowed to identify the most tolerant varieties, while shorter treatments allowed to distinguish intermediate from most sensitive rices. Results of chilling tests applied at the 2- and the 8-leaf stages showed a high correlation. Low-temperature electrolyte leakage and low-temperature fluorescence were also highly correlated to each other and to survival tests applied at the same development stage. By contrast, weak correlations were observed between low temperature germination and plantlet chilling survival. It is concluded that low-temperature electrolyte leakage and low-temperature fluorescence are good indicators of chilling tolerance during the vegetative growth. The possibility to use a chilling screening procedure applied at this stage in order to predict the chilling tolerance at other development stages is discussed.