Abiotic Stresses and Agricultural Sustainability

Abstract

Abiotic stress is a major factor limiting the yield of crops. Some species are able to acclimate to stresses such as cold, drought, and heat, whereas many cultivated species have a limited capacity to do so. Days to weeks are required to acclimate to a cold and drought stress, whereas plants acclimate within hours to a heat stress. Stress-tolerant plants are able to perceive an oncoming stress and upregulate stress associated genes that produce protective proteins and metabolites. The effect of stress-associated genes, e.g., DNH4, CBF 1, ROB5, and SOD 3, on the stress tolerance of genetically transformed or modified (GM) canola (Brassica) and potato (Solanum tuberosum L.) plants growing both in the field and in growth chambers after subjected to heat, drought, and frost was studied. The effect of these genes on seed vigor, germination, and seed yield was also determined. This was one of the first studies that showed in the field the benefits of GM crops for enhanced stress tolerance. Genetically transformed canola plants were grown at five sites in Western Canada; two sites were mildly drought stressed, whereas the other three sites were severely stressed, especially in the spring. ROB5 and SOD were the main genes that improved overall plant performance. Compared with the control, seedlings emerged earlier with a higher percentage, grew taller, flowered and matured earlier, had larger seeds and higher seed yield. Under mild-stress conditions, plants containing ROB5 yielded higher than the control plants, indicating no yield drag. Genomic analysis of the stressed plants revealed ROB5 plants were overall stressed less than control plants. In plants subjected to 42°C for two days, ROB5 plants produced more and larger seed compared with the control. Plants transformed with either CBF1 or ROB5 were 4°C more frost tolerant than the controls. Canola seeds transformed with ROB5 and SOD germinated sooner than controls at 4°C. Potato seedlings transformed with the above stress-tolerance genes showed a significant yield advantage both in the field and under drought and heat stress conditions in the field in a five-year study. Under severe drought and heat stress conditions, plants overexpressing ROB5, CBF1, DNH4, and SOD had significantly higher yields than control plants. Potato plants overexpressing ROB5 and CBF1 were 2°C more freeze-tolerant than the controls. We have learned from these studies that a single stress-tolerance gene has multiple effects on plant-stress tolerance, growth and development, and yield in the field. Through a combined effort from a team composed of molecular biologists, plant physiologists, and plant breeders, it will be possible to produce non-GMO plants with superior traits listed above.