As climate change increases the likelihood of drought in some parts of the world, there will be a greater need for potato varieties that tolerate arid conditions. CIP researchers and their partners in Uzbekistan have selected potato clones from new breeding lines that tolerate drought, high temperatures and the long days of temperate summer, which is a promising development for farmers and consumers there and other parts of Asia.
According to Carlo Carli, a CIP Regional Research Scientist in Central Asia, climate change models predict that the Aral Sea Basin, which includes Uzbekistan, Kyrgyzstan, Tajikistan, Turkmenistan and parts of Kazakhstan, will become increasingly arid as the atmosphere warms. He and his colleagues are consequently working with the national agricultural research systems (NARS) in several of those countries to test and select potato clones for tolerance to drought, heat and adaptation to local conditions, with support from the German Ministry of Economic Cooperation and Development (BMZ). Carli explained that such varieties could both increase farm yields and reduce the need for potato seed imports, which are expensive and don’t always produce well in the region’s dry climate.
Potatoes produce more food per liter of water than most grains, which has made the crop increasingly important in Asia’s arid regions. A good potato crop requires 400 to 800 mm of water, which under a plant density of 40,000 plants per hectare, corresponds to 100 to 200 liters of water per plant, depending on climatic conditions, soils and duration of the growing season. However, vast areas of Central Asia get less than 250 mm of precipitation annually.
Carli observed that the Tashkent region of eastern Uzbekistan, where he and his colleagues have conducted field trials, is an appropriate area for such research because potato farmers there are already dealing with water shortages due to competition with other crops, such as cotton. Carli and his colleagues have run field trials with 64 advanced clones bred by CIP to compare their development under normal, water deficit and severe drought conditions. They selected genotypes with drought tolerance and other desirable traits, such as virus resistance, high yield, marketability and storability, while working with local farmers to identify which varieties they prefer.
The team determined a Drought Tolerance Index (DTI) for each clone, and compared it to a Harvest Index (HI), which refers to the weight of the tubers compared to the rest of the plant. They found that dry matter increased in potatoes under water stress in almost all the genotypes tested, and that plants dedicate more energy to producing tubers under drought conditions.
Many of the CIP-bred clones didn’t produce well in the Central Asian summer, but some virus resistant genotypes showed adaptation to temperate and drought conditions. Two of them, Sarnav (CIP 397077.16) and Pskem (CIP 390478.9), performed especially well in field trials and were released as new varieties in Uzbekistan in 2011. However, researchers subsequently discovered that in the lowlands, Sarnav develops bitterness as a result of the long, hot days in July and August, which is when most potatoes are grown in the region – during the second growing season of the local double cropping system.
Carli noted that the selection of clones for multiplication and release by the local NARS was a milestone in an ongoing process of breeding and development of varieties that tolerate drought and high temperatures. He added that another important trait they are selecting for is earliness, since farmers in the Aral Sea Basin would like potatoes that produce in 90 days, in order to grow them between two consecutive wheat crops and avoid leaving the land fallow, as is normally done in the region. He and his colleagues are running field trials on a new generation of CIP clones bred to respond yet better to the region’s temperate conditions and the needs of local farmers.
Carli explained that CIP’s work with the NARS in Kazakhstan, Tajikistan and Uzbekistan is part of a long-term process that aims to help farmers produce better harvests with less water. He added that potato varieties that do well under the semi-arid, temperate lowland conditions of the Aral Sea Basin could be of great benefit to farmers across Central Asia, including Afghanistan and Northwest China, or other temperate regions of the world where water is scarce.