At least two grasses—sugarcane and sweet sorghum (see page 198) produce stems filled with sugar. Apparently, nobody thought to look for this trait in pearl millet until the 1980s, when some Indian scientists stumbled on some during a germplasm-collecting expedition in the southern state of Tamil Nadu.15 In the area around Coimbatore and Madurai, they found types that at maturity contained more than twice the normal amount of soluble sugars.
These sweet-stalk types had long narrow leaf blades, profuse nodal tillering (with asynchronous maturity), short, thin spikes, and very small grains. They could be easily identified by chewing them at the dough stage.
The sweet-stalk pearl millet is used as a fodder that is usually harvested in September, and a subsequent ratoon crop can be taken for grain and straw. The farmers consider them to be superior feedstuffs because livestock love the sweet stalks.
As can be seen from the above, pearl millet contains a wealth of genetic strengths and offers almost countless opportunities for innovation and advancement. Eventually, biotechnology could have a huge impact on such a diverse crop. It could, for example, be used routinely to transfer pieces of DNA from variety to variety or from the large numbers of wild Pennisetum relatives (or even from other genera). Probably, it is only a matter of time before techniques for this (by using vectors or electrophoration, for example) are developed.
Such transfers are most effective when the crop's protoplasts (wall-less cells) can be regenerated into whole plants. Although it is not yet possible to regenerate protoplasts in pearl millet, it is possible to regenerate suspension cultures (including those of pearl millet x napier grass hybrids) into whole plants.16
Perhaps the best way to codify the enormous diversity of this crop is to create a chromosome map (see box, page 34). This is likely to help make possible all sorts of advances in pearl millet. The task should be easier than with many crops. Pearl millet is a diploid with seven fairly large chromosomes and a large number of genes that are already known and definitively mapped.