The unknown ancestor of the broad bean

Vavilov had clearly been strongly influenced by his host in Algeria when he wrote that “Here it is to some extent possible to solve the riddle of the origin of some cultivated plants. It was just here that Trabut found the interesting wild bean mentioned above, Vicia pliniana (Trabut) Muratova, which undoubtedly is genetically especially closely related to the cultivated forms of the small-seeded, black beans of Afghanistan and India.” Although he doesn’t say as much, he seems to be implying quite strongly that the “wild” Vicia pliniana, found and described by Trabut, is indeed the ancestor, or a very close wild relative of, the cultivated bean V. faba. Alas, this seems not to be the case. V. pliniana is no more than a synonym for V. faba subsp. faba var. minor.

Some of the foremost experts on Vicia taxonomy have reviewed the “confused” taxonomic relations of the fava bean with its allies, and have concluded that “after extensive taxonomic investigation the progenitor has not been identified.” ^[1] Given how much interest there has been in the species in recent decades, it seems unlikely that the ancestral species has been found yet not recognized. So perhaps it has not yet been found. If the wild relative does exist, it is likely to be growing either in the Near East or in Afghanistan, “where the most primitive forms of V. faba occur”. The Near East has been scoured by collecting missions. That leaves Afghanistan. Maxted and his colleagues describe the country as “seriously under-collected” and urge that “forage legume collections in this area should be given a high priority.” There are, of course, other priorities there right now, but that shouldn’t stop a visit by an intrepid Seed Hunter at some point.

Why does any of this matter? Because faba beans matter. According to FAO, in 2006, 2.6 million ha were planted and 4.6 million tonnes were harvested, with about 1.05 million ha planted with faba bean in China alone. Ethiopia, Morocco and Australia cultivate 427,719, 169,000 and 153,000 ha, respectively. Unlike other grain legumes, world trade in faba beans is significantly lower, with most produce consumed locally, where it is an important source of protein. Breeders and farmers looking to improve the performance of faba beans could turn to wild relatives, but the known wild relatives have different numbers of chromosomes from the cultivated types, and the survival of crosses is very poor. The true progenitor might act as a bridge to transfer useful traits from wild relatives into cultivated V. faba.

As for the existing diversity in the species most closely related to V. faba, things are not looking good. Nigel Maxted and Shelagh Kell, in a comprehensive report on crop wild relatives for the FAO Commission on Genetic Resources ^[2] recommend:

• the establishment of new reserves in Syria and Turkey for the active conservation of V. faba‘s closest wild relatives;
• systematic collection of those wild relatives for genebank conservation;
• a continued hunt for a possible true ancestor, focussed on southeast Turkey, Iran and Afghanistan;
• on-farm projects to conserve the existing diversity of faba beans, “particularly in areas with less developed agriculture”;
• and a specific effort to relocate and collect one of V. faba‘s most primitive relatives, V. faba subsp paucijuga, which might still be found in Afghanistan, India and Pakistan.

That’s enough to be getting on with.

Notes:

1. Maxted, N., Khattab, A. & Bisby, F.A., (1991). Domesticated legumes and their wild relatives: newly discovered relatives of Vicia faba L. do little to resolve the enigma of its origin. Botanika Chronika, 10: 129-159. [↩]
2. Maxted, N. and Kell, S. P., (2009). Establishment of a Global Network for the In Situ Conservation of Crop Wild Relatives: Status and Needs. FAO Commission on Genetic Resources for Food and Agriculture, Rome, Italy. 266 pp. PDF somewhere here; good luck with finding it. [↩]

Tagged as: Domestication, Wild Relatives