ICRISAT News, March 2018

Figure: Disease and salinity resistant pigeonpea, currently under evaluation, might soon reach millions of Indian farmers. PC: Michael Major/Crop Trust

Recently, scientists found that more frequent flooding caused by storm and rainfall along with erratic temperature are responsible for the resurgence of phytophthora blight, a devastating disease that weakens pigeonpea stems irrespective of soil types and cropping patterns. With climate change, new invasive pests and changes in the farming landscape, strategic pulses like pigeonpea can dramatically fail. Crop breeders race against time to develop varieties that can adapt or withstand new risks but are sometimes at a loss to find appropriate traits from the pool of cultivated germplasm. However, their distant cousins (crop wild relatives) may harbor the qualities needed by the food crop to cope against emerging threats.

Finding sources of resistance in crop wild relatives

Pigeonpea is an important pulse cultivated mainly in rainfed marginal lands of Asia, Africa and the Americas on 5.41 million hectares with an annual production of 4.49 million tons (FAO, 2016). India alone accounts for 72% of the area and almost two thirds of the global pigeonpea production. One main reason yields are low is because varieties grown by farmers are no longer resilient to recurrent or new diseases like phytophthora blight. The insect pest, Helicoverpa armigera Hübner, commonly known as the ‘pod borer’ continues to be a threat to all grain legumes. Soil salinity is another constraint to pigeonpea productivity which impairs seed germination and plant development as domesticated pigeonpea has unfortunately lost much of its genetic diversity to tackle these issues.

Untouched by humans, wild relatives of domesticated crops have adapted to harsh environmental changes and have developed resistance/tolerance to diseases, insect pests and climate extremes. These attributes can be harnessed from the wild relatives and crossed with domesticated crops to develop what plant breeders call pre-breeding introgression lines (ILs), aiming at creating new varieties that are high yielding and more resistant to extreme climate.

With an evolutionary distance of over 3,500 years, crossing wild relatives with domesticated pigeonpea is a delicate affair and calls for an intervention by a meticulous “plantsmith”. First, desirable traits from crop wild relatives need to be identified. Then suitable domestic recipients have to be selected for crossing. In pigeonpea, “The bottleneck is due to cross-incompatibility between cultivated and wild species, the likely transfer of undesired traits (linkage drag), and sterility in interspecific crosses, thus making it difficult to directly utilize wild species in breeding programs,” explains Dr. Shivali Sharma, Theme Leader – Pre-breeding Genetic Gains Program, ICRISAT.

See http://www.icrisat.org/distant-cousins-of-domesticated-crops-harbor-traits-to-feed-a-hungry-planet/