Exploring the American Tropics is Still a Relevant Input to Bean Science.

‘How many beans are there, and which are they?’, is a question of interest to the botanist and the breeder that has been there since Linnaeus in 1753. It is only around the first International Legume Conference in Kew in 1978 that a precise definition of the genus Phaseolus came through; yet its exact content was unknown. At that time, the American origin of the common bean and the other three bean cultigens (which eventually will be demonstrated to be four) was a strong possibility, but the full history of the domestication of beans was pending to be written. In launching important initiatives for bean breeding in the tropics, CIAT and its partners had to establish important collections of bean diversity as the very base for genetic progress, and it was my good fortune to be associated early in this endeavor. The job was thus to add ‘useful’ genetic diversity to the collections, avoiding to make duplicates of what was already there.

The outcome of thirty years of work (29 explorations in 14 countries of Latin America with over 3,000 new samples made, and studies carried out in 66 museums and herbaria) is three-fold. First, the content of our collections has experienced a shift towards a better representation of diversity per se, with more wild species (twelve of them new, from Mexico and Central America) and forms. The approach in the explorations was shown later as appropriate, given the founder effect that went with the domestication of all five bean cultigens (and given the capacities of marker assisted selection today). The wild ancestors of the five cultigens are now better represented in the collections. Explorations in Ecuador and Peru allowed the finding of a wild common bean close to the root of the species, and the ancestor of the Big Lima. Second, the field work closely linked to the work in the lab in the US and elsewhere has opened a new way at considering species relationships and the structure of genepools, with consequences for the taxonomy and breeding programs as well. The sections represent now more natural entities and groups of shared phylogenetic history, with real or remote potential in wide crossing. Bean species, many of them one-million years old, came into being because of isolation and long distance migrations under climatic oscillations during the early Quaternary. Migrations through the Isthmus of Panama allowed genepools of common bean and Lima bean to acquire most of their unique characteristics long before people came to the Americas. Third, the data gathered in the field and the museums, now used by genebanks, conservation agencies and biodiversity institutes with the increased capacity created by computerized geographic analysis could help to orient conservation activities, with a priority setting in space and time. One can tell which bean populations are at risk along their natural range, given the rapid change in land use in places close to urban or coastal areas.

This is a time and place to express gratitude to the colleagues and institutions in the United States who have supported these explorations and germplasm work with so much patience. I have seen Eden still present in several fields and wild places of the Americas before (irreversible) changes, I have tried to document the unknown, and to answer the above question. I have been very fortunate to see many bean collections valued equally by farmers and breeders, and bean intuitions confirmed by eminent molecular geneticists and taxonomists. Bean genomics will tell us how gene regulation works in that or another species or accession, causing us fascination and joy, just as when we can add another bean to the Neotropical heritage. Thank you all !