Recent research is uncovering a combination of key genes, quantitative trait loci and molecular networks that mediate plant responses to drought, salinity, heat and other abiotic stresses.

Despite these advances there are still gaps in our knowledge particularly in the molecular mechanisms underpinning abiotic stress tolerance in important crop species such as potato. Understanding these processes is essential for breeding or engineering stress-tolerant crop plants.

Previous studies in potato have demonstrated the adverse effect of high temperature and drought stress, impacting on assimilate partitioning, photosynthetic rate, tuber initiation, tuber growth and dry matter content.

However the heat and drought tolerance of existing germplasm is poorly understood and breeders beginning programmes to improve crops for resistance to abiotic stress have little guidance on appropriate germplasm.

Changing climate

Increased frequency of heat stress, droughts and floods negatively affect crop yields beyond the impacts of mean climate change, with impacts that are larger and occurring earlier, than predicted using changes in mean variables alone. This is important in the context of Global Food Security as well as being particularly relevant to the Scottish potato seed industry.

The Scottish industry must produce products for climatic zones that are already seriously affected by elevated temperatures and drought as well as preparing for future climate changes more locally. As the higher yielding cultivated varieties grown in temperate regions largely derive from coastal Chilean stock, most UK varieties have low resistance to extremes of heat and water stress.

For these reasons the cell and molecular sciences abiotic stress research group work is focused on the genetic, molecular and biochemical characterisation of traits associated with sustainable crop development under changing climatic conditions.

Figure 1: Workflow of stem cutting tuberisation assay used to screen for heat tolerance.

Figure 2: Effect of heat stress on tuberisation potential.

As water availability is expected to be the most prominent constraint to increasing agriculture production due to decreasing and often erratic rainfall distribution, crop management practices will play an important role to alleviate the problem. However environmental and economic sustainability is likely to be better achieved if breeding endeavors to develop efficient water-use and drought tolerant varieties are successful. Understanding the genetics and molecular physiology of water use efficiency and drought tolerance are avenues currently under investigation.

Figure 3: Canopy temperature variation in potato genotypes measured through a high throughput rapid remote sensing method (Near Infra-Red thermography). Visual image and Corresponding infra-red thermography image are shown.

Heat stress has severe effects on potato plant growth and development. High temperatures reduce the number of stolons and tubers, and alter carbon partitioning to the tuber, resulting in reduced tuber yield and quality. Potato is best adapted to cool temperate zones; however the forecasted climate changes due to global warming are expected to expose the crop to high day and night temperatures. An additional heat stress phenotype is manifested by potatoes grown at cool temperatures interrupted by periods of high temperature. The main features are heat sprouting, chain tubers and second growth of tubers. It has been suggested that these effects are due to a fluctuation in the level of tuberisation stimulus that causes tuber formation to alternate with more stolon-like growth. We are currently investigating biochemical and molecular changes that occur under heat stress conditions. We intend to use this knowledge to help us breed for potato varieties that are more resilient to elevated temperature and temperature fluctuations.

Figure 4: Leaf microarray data showing up-regulation of genes involved in heat stress at 30?C. Leaf tissues were harvested over a 24h time period.