Vegetable biology

The search for primitive legumes

In spite of the economic importance of legumes, a full picture of this large family has yet to be sketched. To shed more light on these plants, Anne Bruneau, a professor in the Vegetable Biology Research Institute at University of Montréal, has just received funding from the National Science Foundation in the United States. She plans to complete the sampling and carry out a more rigorous classification. And she will do all this in a context where taxonomy, a long-neglected science, acquires new relevance.

Legumes account for some 18,000 species, divided into three subfamilies. The first, the papilionoids, includes the cultivated plants we know so well, such as peas, beans and soy. The second subfamily, the mimosoids, is made up of trees such as the acacia and mimosa. The third and last, the caesalpinioids, comprises about 2,000 species of large tropical trees that are still not well known. Anne Bruneau has been working on these trees for nearly 10 years.

It’s quite a leap from large tropical trees to the green pea. Yet the fossil record confirms that the caesalpinids, which appeared 100 millions years ago, are the ancestors of all legumes. Some of these trees also able to fix nitrogen in the soil, a characteristic that accounts for some of the agricultural interest in legumes, although the origin of this ability is still unknown.

The caesalpinioids grow in the humid forests of South America, Africa and Asia. In the past, researchers worked independently: Europeans in Africa and Asia, Americans in South America. As a result, some species are poorly classified or not classified at all, and some types have been incorrectly placed in separate groups. It’s a real mess!

In order to place this classification on firmer footing, the National Science Foundation has awarded a $300,000 grant to Anne Bruneau and her two colleagues, an American paleobotanist from George Washington University and an English taxonomist who specializes in legumes. The Montréal researcher will contribute her expertise in molecular biology.

The work will extend through 2007. Although Dutch researchers have harvested a collection of representative specimens, Anne Bruneau and her colleagues plan to go back into the field to complete it and identify new species. The three researchers will alternate on one-month trips to exotic destinations: Madagascar, Brazil, Asia, East Africa, Venezuela, etc. Working in a rain forest is no walk in the park. Massive deforestation of tropical forests has made this collection and classification work urgent. “Because they are so large, these trees are frequently cut down,” the researcher laments. “We won't have many more chances to document them and better understand the origin of legumes.”