Phaseolus vulgaris germplasm resources and tolerance to phosphorus deficiency
1994
Beebe, Stephen | Yan, Xiaolong | Ochoa, Ivan | Lynch, Jonathan
Germplasm resources of Phaseolus vulgaris consist of both wild ancestors and cultivated genotypes. A total of some 24,000 accessions are presently available from the CIAT gene bank. Investigations to date have demonstrated that wide genetic variability exists in common beans for the ability to tolerate phosphorous (P) deficiency. A broadbased sample of 364 landraces and wild beans from distant geographic origins was evaluated under high and low P. Wild beans were typically very sensitive to P deficiency, suggesting that P tolerance was probably selected during or after domestication, and therefore could have evolved independently in different gene pools and races. Yield data suggested that low P tolerant genotypes occur more frequently in some regions than in others. For example, the State of Chiapas in Mexico was the source of several superior genotypes. Another pocket of low P tolerant landraces was identified in Amazonas province, Peru. The broad genetic variability represented in accessions from Chiapas, from Amazonas, and from other regions invites speculation that some tolerant accessions may possess contrasting physiological mechanisms of tolerance. Several traits possibly related to P efficiency have been recognized in tolerant genotypes, including root structure, rhizosphere acidification and acid phosphatase activity. However, it has not been established that any of the fore-mentioned traits are responsible for the observed low P tolerance. Research to identify mechanisms of low P tolerance would aid efforts to recombine mechanisms, to understand environmental effects on P efficiency, and to obtain molecular markers for relevant traits.
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