Genetic Variation for Phosphorus Efficiency of Common Bean in Contrasting Soil Types: I. Vegetative Response

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Abstract
Phosphorus deficiency is a primary limitation to bean (Phaseolus vulgaris L.) production in the tropics. Bean genotypes differ in their P efficiency, defined as growth and yield in low P soil. Traits conferring P efficiency may be useful only in specific soil types, or may represent more general adaptations to low P availability. This information is essential in selecting and breeding more P efficient bean germplasm. Our objective was to determine if P efficiency in bean is limited to specific soil types. Sixteen contrasting genotypes were grown in pots of Andosol, Ultisol, and Oxisol soil at three levels of applied P in the tropics. At 35 d after planting, shoot growth, root growth, P accumulation, and symbiotic status were evaluated. Genotypes differed significantly in P efficiency. The relative ranking of genotypes for shoot biomass, root biomass, root length, or P accumulation under all P levels was not affected by soil type and was not related to the degree of rhizobial or mycorrhizal infection. Large‐seeded Andean genotypes were superior to small‐seeded Mesoamerican genotypes, especially under low P. Small‐seeded Mesoamerican genotypes were more responsive to added P. We conclude that (i) large genetic variation for P efficiency exists in tropical bean germplasm, (ii) this variation reflects a general adaptation to low P availability rather than an interaction with specific soil types or soil microbes, (iii) large‐seeded germplasm appears to have superior P efficiency under low P availability, and (iv) Mesoamerican genotypes are more responsive to added P.

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