Morphological and cytological characters associated with low-temperature tolerance in wheat (Triticum aestivum L. em Thell.)

Attempts to associate morphological or cytological characters with low-temperature (LT) tolerance in wheat (Triticum aestivum L,. em. Thell.) and other members of the Triticeae group have met with ambiguous or contradictory results. Consequently no single character has emerged that can be considered a reliable predictor of LT tolerance. Twenty-six winter wheat cultivars of diverse origin were analyzed to determine the association among leaf length, width, area and cell size (guard cell length) and their association with LT stress tolerance. Measurements were made on plants grown at 4 degreesC and at 17 degreesC to determine if expression of LT tolerance associated characters was temperature dependent. At 4 degreesC, all individual leaf characters measured, including cell size, were very highly correlated with LT tolerance and with each other. Undisturbed plant height was not significantly correlated with LT tolerance until 5 wk of growth at 4 degreesC and reached its highest correlation at 10 wk when the plants were on average at their most prostrate state of growth. Growth at 17 degreesC resulted in much weaker relationships among all characters. At 4 degreesC short narrow leaves and small cell size were the best indicators of LT stress tolerance. Prostrate growth habit of plants grown at LT was also a good indicator of plant LT tolerance, but measurements of this character did not improve prediction equations based on leaf characters and cell size.