Frost Tolerance of Triticum durum (Desf.) Genotypes in Soils with Various Moisture Contents

Abstract

The frost tolerance of nine T. durum (Desf.) genotypes of various origin was determined in the phytotron at -13.5°C at different soil moisture contents. At the end of preliminary growth (stage 4 on Feekes scale) and during the first phase of hardening five different soil moisture content levels were established by adding various quantities of water. The majority of genotypes survived freezing best in very dry soil (water content was 28.3% of natural soil water capacity). Cultivars with poorer frost tolerance suffered the greatest mortality in wet (water content 67.3%) or very wet (water content 74.8%) soils. For all the genotypes a negative correlation was observed between the survival percentage and the soil water content. The frost tolerance of cultivars with good winter hardiness was not greatly influenced by the soil moisture content prior to freezing. For the other genotypes close correlations of various sizes were found between frost tolerance and soil water content. The scoring data of plants that survived freezing and exhibited regrowth also reflected the fact that freezing caused the least damage to the plants in the very dry treatment. In a similar experiment on bread wheat differences in soil moisture content during freezing had little influence on the test results of cultivars with excellent frost tolerance, while for those with moderate or poorer frost tolerance, the survival values of plants frozen at different soil moisture contents showed deviations of more than 50%. These results are confirmed by the present experiment with durum wheat. Soil moisture content influences the concentration of the cell solution in the plants, which in turn affects the survival of the plants due to ice formation at below-zero temperatures.