Coevolution and Migration of Bean and Rhizobia in Europe

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Paula A. Rodino, Marta Santalla, Antonio M. De Ron, and Jean-Jacques Drevon

Abstract The legumes crop common bean is one of the most important crops for the human nutrition common bean is the protein basis from developing countries. Common bean presents many limitations such as the deficiencies or toxicities of minerals in soils. These limitations in common bean production regions occur throughout the world. To overcome mineral deficiencies and toxicities, common bean growers must use corrective soil amendments. Symbiotic nitrogen fixation (SNF) is important as a source of N for agriculture, because the use of nitrogenous fertilizers has resulted in unacceptable levels of water and atmosphere pollution and by nitrate and N2O emissions, contributing to the increase of greenhouse effect. The common bean grown in Europe, and other continents, is the result of a process of domestication and evolution, from wild forms found exclusively in the Americas, and it is possible to distinguish two major domestication centres, Andean and Mesoamerican centers. Most of the European germplasm is from Andean locations since the type T phaseolin pattern is found in their seeds. It is thought that Mesoamerican lines were less popular because of their lower adaptability to winter cold and to short duration summers. Subsequently, new cultivars may have evolved within and between the two gene pools in Spain and Portugal making the Southern Europe a secondary center of diversity for the common bean. The microorganisms associated with the common bean plant for its symbiotic nitrogen fixation may exhibit a similar arrangement of genetic diversity in Mesoamerica and Andean gene pools. R. etli bv. phaseoli is the dominant microsymbiont in both the Mesoamerican

Legumes Breeding Group, Plant Genetic Resources Department, Misión Biológica de Galicia,

P.O. Box 2836080, Pontevedra, Spain e-mail: [email protected]

e-mail: [email protected]

e-mail: [email protected].

INRA-Montpellier-SupAgro, UMR1222, Rhizosphere et Symbiose, 2 Place Viala, 34060,

Montpellier, France e-mail: [email protected].

E. Lichtfouse (ed.), Sociology, Organic Farming, Climate Change and Soil Science, 171

Sustainable Agriculture Reviews 3, DOI 10.1007/978-90-481-3333-8_7, © Springer Science+Business Media B.V. 2010

and Andean centers of origin. Many other species have been found in bean nodules in region where they have been introduced. In Europe, rhizobia strains that nodulate common bean have a narrow genetic diversity that was correlative to beans being an introduced crop. In this respect, the large number of rhizobia species capable of nodulating bean supports the premise that bean is a promiscuous host and a diversity of bean-rhizobia interactions exists. Since there seems to be a large variation in the capacity of bean genotypes to nodulate with a large range of host-or non-host specific strains, this knowledge could be used to enhance the symbiosis and possibly to enhance nitrogen fixation.

Keywords Common bean • Diversity • Domestication • Evolution • Origin • Rhizobia 7.1 Introduction

Deficiencies or toxicities of minerals in soils in common bean production regions occur throughout the world. To overcome mineral deficiencies and toxicities, common bean growers must use corrective soil amendments such as lime (Fageria et al. 1995), manure or composted manure (Tarkalson et al. 1998), and fertilizers rich in macronu-trients and micronutrients such as N, P, B, Fe, and/or Zn (Henson and Bliss 1991). Symbiotic nitrogen fixation (SNF) is important as a source of N for agriculture, because the use of nitrogenous fertilizers has resulted in unacceptable levels of water pollution and the eutrophication of lakes and rivers. However, international emphasis on environmentally sustainable development with the use of renewable resources is likely to focus attention on the potential role of SNF in supplying N for agriculture.

Common bean (Phaseolus vulgaris L.), domesticated in Mesoamerica and Andean South America, was introduced into Spain after the colonization of the Americas (Gepts et al. 1986). Currently common bean is the world's most important grain legume for direct human consumption and are staple crops serving as the primary source of protein nitrogen in the diet for developing pays. In Europe, the importance of the common bean is due to a change in nutritional habits and a greater demand for healthy and functional products. Large germplasm collections are maintained in different countries. New cultivars are displacing landraces but farmers still grow landraces for personal consumption and sale in farmer's markets. Genetic variability found for seed colour, size, shape, and other characteristics is very high among genotypes grown by farmers. The Legumes Breeding Group at the Mision Biologica de Galicia - Spanish Council for Scientific Research (MBG-CSIC) has an Iberian common bean germplasm collection and oversees the task of further collecting, evaluating, and maintaining the landraces (De Ron et al. 1997). Knowledge of patterns of genetic diversity among landraces and their relationships with new cultivars helps broaden the genetic base and maximizes use of available germplasm. In spite of increasing use of the DNA-based markers for studying genetic diversity, study of phenotypic variation in a germplasm collection is crucial for determining adaptation, agronomic potential, and breeding value of landraces.

The Leguminous as common bean, have formed an important part of crop cultivation systems performing relevant roles in sustainable agricultural practice, effective management of fertilizer, improving soil health, and protection of surface and ground water from contamination. Among these crops, common bean can satisfy a great proportion of their nitrogen requirement by means of SNF. Nitrogen availability is often a limiting factor for crop productivity, particularly in developing countries. Moreover, the use of chemical N must be limited for the preservation of the environment, particularly in Europe where rates of N fertilization have increased steadily, in addition to manure recycling and significant N deposition from the atmosphere (Fink et al. 1990; Goulding et al. 1998; Graham and Vance 2000). Rhizobia are soil bacteria studied for their ability to establish nitrogen fixing symbiosis (Fig. 7.1). The SNF still provides more nitrogen to the agricultural ecosystems worldwide than the total amount of N fertilizer applied. This system could constitute an ecologically acceptable alternative to the high application of N fertilizers, particularly in Europe, and an economic alternative to the limited access of developing countries to N fertilizers. Thus, this review aims at summarizing the most recent information regarding the evolution and the diversity of common bean accessions and the soil bacteria as rhizobia that can be associated with them. The main topics will be: (i) origin, domestication, and dispersal routes of common bean, (ii) phaseolin is an important evolutionary marker, (iii) diversity of rhizobia, and (iv) conclusions and perspectives.

Fig. 7.1 Association of common bean with rhizobia. This association provides the development of nitrogen fixing organs, called nodules, in the roots of plant-host

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