Heat stress characterization of wheat cultivars using NMR and allied technique: A rapid and non-invasive method

High temperature limitation of crop yield and quality is a well-recognized problem in India and many other countries. To make significant progress in developing tolerant genotypes, identification of heat tolerance mechanisms, the extent of genetic variability for these and development of suitable methods to identify tolerance characteristics in large breeding populations are very crucial. The (1)H NMR transverse relaxation time (T(2)) have been used widely to describe the water status as well as heat and freezing injury in plant tissues. T(2) of tissue water has been shown to be related to the water content of the plant fissile, properties of water in different parts of the tissue and interactions with macro-molecules. The study suggests that the sharp decline in T(2) corresponded to a loss of membrane integrity. An increase, on the other hind, was observed before the decline, probably due to the release of water held in the hydration layers. The temperature dependent hysteresis in T(2) indicates that the changes in T(2) reflect irreversible changes in membrane integrity. Heat tolerant varieties, which suffered less membrane injury, maintained T(2) of leaf water protons to higher temperatures than sensitive varieties. Therefore, NMR offers a non-destructive and non-invasive method for characterization of water status in many biological tissues including crop species.