Abiotic Stress

Abiotic Stress plants are rooted to the ground and are greatly affected by environmental perturbations. Plants are exposed to environmental stress when conditions negatively affect their growth and development and their productivity regarding flowers, fruits, or grain yield. When environmental stress causes an excessive change in the chemical and physical environment where the plant grows, it is called abiotic stress. Abiotic stress includes extreme heat or cold, saline soils, drought, flooding, mineral deficiencies or excesses, and insufficient or too much light. Ozone is also phytotoxic. The effect on the plant depends on the plant's growth stage, the duration of the stress, or even if multiple abiotic stresses are imposed simultaneously.

A plant's response to abiotic stress includes changes in its gene expression and cellular as well as physiological metabolism. Direct response can be triggered, for example, by lack of water under drought stress, or there may be a stress-induced injury such as loss of membrane integrity. Depending upon the severity of the stress, the average loss in crop productivity due to abiotic stresses may exceed 40-50%. Successful application of classical breeding or biotechnological interventions may produce stress-tolerant crops, which has become very important due to climate change as well as increasing world population. However, any crop improvement program would require donors for tolerant traits. The source of these donors would be traditional genotypes (often called landraces) adapted to extreme environmental conditions which have evolved over hundreds of years in those harsh environments. Which brings in the concept of biodiversity and its preservation in the form of seeds from these landraces in seed/gene banks? Eleven Genebanks are managed by CGIAR (Consultative Group on International Agricultural Research) Centers, which conserve more than 700,000 accessions of cereals, legumes, grasses, tree species, and root and tuber crops, as well as bananas. Many genotypes are the wild relatives of crop species. CGIAR centers have distributed more than a million samples to plant breeders and researchers from more than 150 countries. [Zeba Islam Seraj]