Pigeonpea (arhar or tur) has become the first crop to have its genome fully mapped and that, too, completely in India. The implications of this scientific feat are many, some of which are technically and commercially very significant.
Developed countries, which are investing heavily in genome research in commercial crops to evolve genetically-superior varieties, have little interest in arhar since they neither grow nor consume it. For India, on the other hand, arhar is a key pulse of massconsumption. In fact, its paucity and consequential price spike has contributed to sustaining high food inflation.
India accounts for nearly 75 per cent of the world’s total arhar production and 85 per cent of its consumption. Arhar is a unique pulse in several respects. Every part of this woody leguminous shrub has some gainful use. Its seeds are a rich source of protein, minerals and vitamins and are consumed by a sizable section of the population as daal or sambar and its green pods are cooked as vegetable. Besides, its leaves and grain husk are used as cattle feed; its stem and branches are used as fuel and fencing, and for making thatches, baskets and handicraft items.
Moreover, the arhar crop benefits the soil on which it grows. Its root-nodules in association with bacteria fix atmospheric nitrogen into the soil (about 40 kg a hectare), while its deep-root system improves the soil structure and enhances its organic matter content, lifting the overall soil fertility.
On the downside, however, arhar is a long-duration crop, occupying fields for five to nine months, depending on crop variety. This virtually rules out its inclusion in multiple cropping that is practiced widely in irrigated tracts in agriculturally-progressive regions. This drawback has kept arhar farming confined largely to rain-fed areas where productivity is rather low. Though some shorter duration varieties have been bred over the years, seed scarcity has hindered the expansion of areas under such varieties.
The second major constraint faced by this crop is its vulnerability to such stress factors as water-logging, diseases like plant wilt and pests like pod borers. As a result, the average yield of arhar is quite low, around 8.25 quintal a hectare, against the potential of over 20 quintal a hectare.
According to scientists involved in the genome decoding project, pigeonpea variety “Asha” was selected for genome decoding because it enjoys the highest demand owing to its resistance to common diseases like fusarium wilt and sterility mosaic. The induction of its genes in other arhar varieties will impart these traits to them as well. The resultant new strains would boost the output of arhar and help curtail imports of pulses that have mounted to nearly 3 million tonnes, valued at some Rs 700 crore annually. That makes it imperative for India to invest in arhar research to acquire technology for boosting its productivity.
From a scientific viewpoint, the genome decoding feat is significant since it unfolds the secrets of a complicated genome that has as many as 11 chromosomes and nearly 511 million base pairs of gene sequences. Scientists have identified 47,004 different genes, of which 1,213 control diseases and 152 possess traits like tolerance to drought, heat and soil salinity. The availability of a clear picture of the genetic constitution of this genome – indicating the exact location of genes that control traits like yield, disease and insect resistance and tolerance to high soil moisture and heat – will enable arhar breeders to create made-to-order plants by incorporating the selected genes in them. More importantly, easy access to such genes would help reduce the time taken to evolve new varieties to about half of what it takes now — from about six years to merely three years or so.
The arhar genome project was funded by the Indian Council of Agricultural Research (ICAR) and carried out by a team of 31 scientists led by Nagendra Kumar Singh of the New Delhi-based National Research Centre on Plant Biotechnology. Several institutions, including ICAR institutes at New Delhi and Kanpur, farm universities at Akola (Maharashtra) and Dharwad (Karnataka) and the Banaras Hindu University, were involved in this collaborative effort. Its fruits will be available to all the arhar breeders for churning out new and better crop varieties.
