Diversidade de caracteres radiculares em feijoeiro em dois estádios de crescimento

Abstract

Studies indicate that the genotypes of common bean (Phaseolus vulgaris L.) with high growth in low soil P availability were those with high root mass. Hence, high root development might be a strategy for increase the yield of beans cropping in tropical soils. However, bean growth stage has significant effects on root morphology, which may compromise the use of root traits as selection criteria for plant breeding. This study aimed to study the diversity of root traits in common bean genotypes in two development states. An experiment was carried in pots with 4 kg of soil from the A horizon of an Yellow Red Ultisol, in an 24x2x2 factorial randomly block design with four replicates, with 24 common bean genotypes, two soil P levels (20 and 80 mg P kg-1) and two times of harvest (R7 - pod setting, and R8 pod filling, 11 days after R8). At harvesting, dry mass of stems, leaves and pods, and leaf area were evaluated, and the roots systems were recovered by washing and sieving. Samples of root system were digitalized, and its root area and root length were determinate through digital image analysis. The roots were separated in taproot, lateral and basal roots and nodules, and the nodules were counted and each portion of root system were dried and weighed. The N and P concentrations were determinate in shoots. The mass of lateral and basal roots, the root area, root length, specific root area, and root/shoot rate were the root traits with wider variability in low P. The leaves and the laterals and basal roots were the organs with greater variability in the proportion of allocated biomass. Limitations for N accumulation were observed in low P. The results indicated a higher genotypic variability in the shoots and roots at the second harvested (R8 stage pod filling), that was greater at the highest P level. The evaluation of root traits in common bean to increase efficiency of P acquisition should be carried out in stages after the flowering, when the expression of genotypic variability would be greater.