Inheritance of root traits and phosphorus uptake in common bean (Phaseolus vulgaris L.) under limited soil phosphorus supply

摘要

Scarce information about genetic control of root traits in common bean (Phaseolus vulgaris L.) impedes a more effective exploitation of the reported variability for plant breeding. This work investigated the inheritance of traits related to the root system and P absorption of common bean grown under limited soil P supply. Two experiments were carried out, each one involving one family of crosses comprising six populations (two parental cultivars, F1, F2, and two backcrosses). One plant was grown per pot with 3 kg of soil (7 mg P kg−1 Mehlich-1) and harvested at pod setting. Root samples provided the root surface area and root length by digital image analysis. Considerable additive genotypic effects were detected in both experiments; additive × additive epistases were significant only in the second experiment, whereas dominance effects were seldom significant. Estimated broad-sense heritabilities were 0.55 and 0.51 for root area, 0.50 and 0.47 for root length, 0.51 and 0.61 for root mass, and 0.51 and 0.43 for the total P content, in the first and second experiments, respectively. High genotypic correlation between root mass and root area justifies screening genotypes based solely on root mass. Phenotypic and genotypic correlations between shoot mass and root mass, and shoot mass and total P content, were highly significant, indicating that direct selection for higher shoot growth of bean plants under limited soil P supply would result in increased root mass and P uptake. A scheme for root breeding in common bean towards improving P efficiency should include: matching cultivars with favourable alleles; advance until later generations without any selection; selection of resultant genotypes under low soil P supply via shoot growth; evaluation of promising lines for root growth and agronomic performance.