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.
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.
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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