Breeding for drought stress tolerance
Drought can be defined as the absence of rainfall or irrigation for a period of time sufficient to deplete soil moisture and cause dehydration in plant tissues.
Severe drought in parts of the U.S., Australia, and Africa in recent years drastically reduced crop yields and disrupted regional economies.
Even in average years, however, many agricultural regions, including the U.S. Great Plains, suffer from chronic soil moisture deficits.
Two major trends will likely increase the frequency and severity of soil moisture deficits: Although changes in tillage and irrigation practices can improve production by conserving water, enhancing the genetic tolerance of crops to drought stress is considered an essential strategy for addressing moisture deficits.
Soil moisture deficit lowers the water potential of a plant's root and, upon extended exposure, abscisic acid is accumulated and eventually stomatal closure occurs.
Generally three strategies can help a crop to mitigate the effect of dehydration stress: The Drought Resistance terms in summary (Levitt, J.
Dehydration escape involves e.g. early maturing or seed dormancy, where the plant uses previous optimal conditions to develop vigor.
A proper timing of life-cycle, resulting in the completion of the most sensitive developmental stages while water is abundant, is considered to be a dehydration escape strategy.
When the stress is terminal and predictable, dehydration escape through the use of shorter duration varieties is often the preferable method of improving yield potential.
Measurements of CMS have been used in different crops and are known to be correlated with yields under high temperature and possibly under dehydration stress.
Experiments have demonstrated that rice varieties with a thick cuticle layer retain their leaf turgor for longer periods of time after the onset of a water-stress.
As photosynthesis becomes inhibited by dehydration, the grain filling process becomes increasingly reliant on stem reserve utilisation.
Numerous studies have reported that stem reserve mobilisation capacity is related to yield under dehydration stress in wheat.
However, high ABA can also result in sterility since high ABA levels may abort developing florets The concept of combination phenomics comes from the idea that two or more plant stresses have common physiological effects or common traits - which are an indicator of overall plant health.
[15] Recent research breakthroughs in biotechnology have revived interest in targeted drought resistance breeding and use of new genomics tools to enhance crop water productivity.
Other molecular breeding tool include development of genetically modified crops that can tolerate plant stress.
