title: Comparison of inhibition of N2 fixation and ureide accumulation under water deficit in four common bean genotypes of contrasting drought tolerance.
abstract: OBJECTIVE
  Drought is the principal constraint on world production of legume crops. There is considerable variability among genotypes in sensitivity of nitrogen fixation to drought, which has been related to accumulation of ureides in soybean. The aim of this study was to search for genotypic differences in drought sensitivity and ureide accumulation in common bean (Phaseolus vulgaris) germplasm that may be useful in the improvement of tolerance to water deficit in common bean.
  
  
  METHODS
  Changes in response to water deficit of nitrogen fixation rates, ureide content and the expression and activity of key enzymes for ureide metabolism were measured in four P. vulgaris genotypes differing in drought tolerance.
  
  
  RESULTS
  A variable degree of drought-induced nitrogen fixation inhibition was found among the bean genotypes. In addition to inhibition of nitrogen fixation, there was accumulation of ureides in stems and leaves of sensitive and tolerant genotypes, although this was higher in the leaves of the most sensitive ones. In contrast, there was no accumulation of ureides in the nodules or roots of stressed plants. In addition, the level of ureides in the most sensitive genotype increased after inhibition of nitrogen fixation, suggesting that ureides originate in vegetative tissues as a response to water stress, probably mediated by the induction of allantoinase.
  
  
  CONCLUSIONS
  Variability of drought-induced inhibition of nitrogen fixation among the P. vulgaris genotypes was accompanied by subsequent accumulation of ureides in stems and leaves, but not in nodules. The results indicate that shoot ureide accumulation after prolonged exposure to drought could not be the cause of inhibition of nitrogen fixation, as has been suggested in soybean. Instead, ureides seem to be produced as part of a general response to stress, and therefore higher accumulation might correspond to higher sensitivity to the stressful conditions.
authors.affiliation: Departamento de Botánica, Ecología y Fisiología Vegetal, Grupo de Fisiología Molecular y Biotecnología de Plantas del Campus de Excelencia Internacional Agroalimentario, CEIA3, Campus Rabanales, Edif. Severo Ochoa, 1 planta, Universidad de Córdoba, 14071 Córdoba, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Coleto
authors.forename: M
authors.initials: M
authors.lastname: Pineda
authors.forename: A P
authors.initials: AP
authors.lastname: Rodiño
authors.forename: A M
authors.initials: AM
authors.lastname: De Ron
authors.forename: J M
authors.initials: JM
authors.lastname: Alamillo
mesh_terms: D000222:Adaptation, Physiological; D055864:Droughts; D007887:Fabaceae / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005838:Genotype; D009586:Nitrogen Fixation; D014508:Urea / Q000378:metabolism*
chemical_list: D014508:Urea
keywords: Allantoin; Phaseolus vulgaris; Rhizobium leguminosarum; allantoate; breeding; common bean; germplasm; ureide metabolism; water stress