SATrends Issue 92
July 2008
1. Evolution fast forward!!

Did you know that the ancestors of the present day groundnut originated in the valleys of Brazil? As most of us know, the groundnut (also known as peanut) went on to become an important oil, confectionary and a commercial crop of the world. The wild progenitors (diploids) had half the chromosome number of the present day groundnut (tetraploid), had a creeping growth habit, the pods were small with long thread-like stalks called pegs and the kernels did not taste anywhere as good as the groundnuts of today.

Wild species of Arachis Wild species of Arachis.

How did the present day groundnut evolve? Scientific evidence shows that two diploid wild species formed a hybrid. But most seed producing plants reproduce the same way; though with groundnut, a diploid hybrid, or more likely a few hybrids, doubled their chromosome number to form tetraploid plants. The tetraploids evolved to form the present day groundnuts. This did not happen overnight. Researchers say that such an event probably took place some 3500 years ago. It would have been fine if these events continued to happen, giving rise to a wide genetic base. Unfortunately, that was not the case with groundnut. So, the result is that tetraploid cultivated groundnut has a narrow genetic base. A narrow genetic base in this case is the cause of "delicate health" of the crop - it is susceptible to a range of diseases and pests, it cannot grow when water is limited, and grows poorly when the soil is salty.

Scientists are anxious to have new groundnut varieties with new gene combinations to overcome the drawbacks of the narrow genetic base. The natural evolution of tetraploid groundnuts has virtually stopped, so scientists have to simulate nature and produce new tetraploids by first producing diploid hybrids in different combinations, more than nature provided 3500 years back, and produce synthetic tetraploids.

Synthetic groundnut plants "Synthetic" groundnut plants developed at ICRISAT.

Cell Biologists at ICRISAT are doing this now. The development of synthetics, although exciting, is not without birth pangs! Many combinations of diploid hybrids either do not flower or the plants are totally sterile. Multiplying plants with cuttings gives a low success rate. Few diploids/diploid hybrids double their chromosomes when treated with chromosome doubling agents, such as colchicine. Sometimes the doubled ones revert back to diploidy, or produce few flowers. Despite the painful process, efforts have been successful!! ICRISAT has now developed a few synthetics and is in the process of developing a few more. This is not a new line of research for ICRISAT, but the systematic approach is new and encouraging.

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2. Pigeonpea climbing to new heights

Uttarakhand is a hilly state of India, bordering Nepal and China. The elevation ranges from 300 to 7000 meters above sea level. A total of 0.8 million ha is under agriculture and of this, 57.75% is in the hills. The annual demand for pulses in Uttarakhand is 0.3 million tons, but the present production is only 0.06 million tons. To fill the deficit, ICRISAT in collaboration with the Department of Agriculture has introduced a special program to promote pigeonpea in these hills.

Pigeonpea on the Himalayan slopes Pigeonpea growing well on the Himalayan slopes.

The inspiration for this promotion came from the success of pigeonpea in the sloping hills of southern China and the experiments conducted by the Vivekananda Parvathiya Krishi Anusandhan Sansthan (VPKAS), Almora. VPKAS rigorously tested ICRISAT's short-duration pigeonpea ICPL 88039 in the hills, after which ICPL 88039 was released in 2007 under the popular name VL Arhar 1.

To undertake the promotion of this pigeonpea, a special project, supported by the Uttarakhand Government was initiated with ICRISAT in 2006. The first testing program was launched in the 2007 rainy season. A total of 375 on-farm demonstrations were conducted in 13 districts and 67,400 kg of seed was harvested from 112 ha with mean productivity of 600 kg ha-1. The most interesting observation was that elevations above 1500 m, such as Gangolihat, also recorded high yields (1550 kg ha-1). Amazingly, most pigeonpea areas in Uttarakhand are wastelands where no food crop could be grown earlier.

Pigeonpea on slopes ICRISAT scientist with local pigeonpea growers.

In 2007-08 a total of 1183 farmers of 408 villages cultivated VL Arhar 1. The general observations were:

Though it was their first experience of growing pigeonpea, the farmers were happy and plan to grow pigeonpea again next season. The total area in 2008 has increased 15-fold, from 112 ha to >2000 ha. Pigeonpea is a profitable crop with high yields and little inputs. However, the production constraints at different altitudes and important issues like value addition and marketing need to be studied and addressed. Also elaborate programs have been made for large-scale quality seed production, training, and monitoring.

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