Hunting for drought tolerance genes in ancient Andean landraces

Recent problems with food and water resources are reflected by breeders all over the world. Potato was chosen by UN for the crop of the year. It is the world's number one non-grain food commodity, with production reaching a record 320 million tonnes in 2007. Potato consumption is expanding strongly in developing countries, which now account for more than half of the global harvest and where the potato's ease of cultivation and high energy content have made it a valuable cash crop for millions of farmers.

Our ordinary potato is in fact a treasury of human effort and knowledge.
Potato was first domesticated from a plant with small not very tasty and slightly toxic tubers in the Peruvian Andes over 7,000 years ago. After great contribution to its trait by Peruvian peasants potato was turned in a relatively good food crop and carried over to Europe in the late 16th century. Soon potato represents very important food source, unfortunately based on too narrow diversity of varieties. This was fatal particularly in Ireland in the half of 19th century where the food was based mostly on potatoes. The type of weather in 1845 cased great spread of a fungus Phytophtha infestans, that causes potato blight. Great famine followed. About million of people died in Ireland and similar amount safed themselves by emigration - mostly o America.

This was memento to breeders: they should pay attention to this important food crop. Science entered breeding at the beginning of 20th century by the Mendel's formulation of traits transfer from parents to progeny. Thanks to this we may enjoy rich spectrum of potato sorts.
Should be potatoes grown in broad (and changing) climatic conditions the recent traits inherited to potato are not sufficient. After hundred years of Mendel's experiments in the garden of the monastery in Brno, biotechnology provided methods how to transfer genes also from organisms that do not cross.
Looking for genes improving the crop the region of origin is the good place to look at. Resistance to potato blight causing th famine in Ireland was transferred to our varieties from the wild relatives in Peru Solanum bulbocastanum. It was just straightaway to look in this region for genes protecting potatoes from drought. The cold, dry Andean Altiplano gave rise to a number of potato varieties that could tolerate drought.

Many of the ancient potato landraces contain adaptations to different environmental conditions such as different soils, temperature, altitude, and drought. Preservation of these varieties and knowledge of their genetic and adaptive histories are of paramount importance as farmers around the world as breeders try to cope with changes in temperature and water availability and struggle to maintain a food supply for growing populations. The International Potato Center in Lima, Peru maintains the world's largest collection of tubers to conserve the genetic diversity of potato as well as to investigate traits such as resistance to various insects and diseases, as well as to cold, heat and drought.

Drought first causes stomatal closure, reducing CO2 uptake for photosynthesis, reducing plant growth and yield. Plants vary in the types and speed of responses to drought conditions, depending on their genetic and ecotypic backgrounds, but a number of drought responsive genes are conserved across plant taxa. Dr. Schafleitner, of the Germplasm Enhancement and Crop Improvement Divisionof the International Potato Center and his co-workers studied two Andean potato clones under field conditions and used microarrays to to identify genes that are up- and down-regulated under drought conditions.
The scientists identified about 2000 genes that regulate numerous functions, including metabolic changes and cell defence functions. Solute concentrations were increased as a response to drought, lowering osmotic potential, to induce uptake of water from drying soils. The results of this research are used for screening and breeding efforts in crop improvement also for other members of the Solanaceae. Thanks to the work of scientists not only in Peru, but over the whole world who provided tools matching the growing demands of human population, potato may today serve as important food crop in solving the global food problem.