We've previously introduced some pioneers in modern agriculture as featured in the Dec. 4, 2008, issue of Nature magazine.

One group is working to conquer stem rust, a devastating fungus attacking wheat.

Another is working to convert crop plants, nearly all of them annuals that have to be planted each year, into perennials that will be superior in efficiency and better for the soil. Let's finish the final three of these geniuses today.

Cassava is a tuberous perennial crop native to the New World tropics, but now incredibly important in other tropical countries, especially in Africa. The bulbous roots can be made into flour and starch. But cassava is quite poor in nutrients.

Richard Sayre, a botanist at Ohio State University, employed a young Nigerian student who introduced him to the crop, and Sayre decided to tackle its problems of nutrition. It grows well in poor soils and requires very little labor as a crop, so it is ideal for impoverished people. But some varieties are very bitter, even toxic. Sayre is using both traditional methods of plant breeding and biotechnology to re-build the plant. He and his team are now in private industry and receive major funding from the Bill and Melinda Gates Foundation. His goal is to produce a variety sufficiently nutritious that 500 grams per day (about 1.3 pounds) will yield a minimum daily allowance of protein, vitamins A and E, and zinc and iron. Genes for viral resistance also are being incorporated. In total, this may require introducing as many as 15 new genes into the plant. Some strains moving toward that goal will begin field trials in Nigeria this year.

Another star representing an entire group of workers is Julian Hibberd of the University of Cambridge in England. In 2006, he was invited to a brain-trust meeting convened by IRRI, the International Rice Research Institute, which is itself an outgrowth of the Green Revolution of the 1960s. The convener was IRRI's John Sheehy, who had an incredibly visionary project in mind.

Plants make their food (glucose) by photosynthesis, of course, using sunlight to metabolize CO2 and water to make sugar and oxygen gas. But there are two basic ways to do it. C3 is the more primitive and least efficient. C4 is the much more productive system. But rice is a C3 plant. Sheehy posed to his cloistered scientists the question of whether C3 plants could be transformed into C4. Hibberd has made that his life's mission, also with support from Bill and Melinda Gates.

It's a tough job. The C4 plants have very different leaf structures and two rather than just one type of chloroplasts. But it appears that C4 has evolved numerous times from C3 plants in nature. So Hibberd and his group are identifying all the critical genes and will try to introduce them into C3 plants. It will likely increase the productivity of rice plants by 50 percent if successful.

A totally different approach is being employed by Zhang Jianhua, raised as a peasant in China's rural collectives. In the tiny villages, each family was given a small plot to raise their own crops. As a teen, Zhang noticed that his family's plot was just a bit higher than others above the irrigation source, and its rice was drying out sooner. But surprisingly, it produced heavier kernels.

Zhang has now been educated in China and England and is a major spokesman for "deficit irrigation." Plants faced with drought often convert their major efforts to making seed. Zhang has taught ways to exploit this to China's wheat producers. They are now using only about half the water they were a decade ago.

Agricultural and biology teachers: Zhang's story alone is worth getting the full story in Nature to share with your classes.

See what people are talking about at The Community Table!