Performance of Mesoamerican bean (Phaseolus vulgaris L.) lines in an unfertilized oxisol

. Common beans (Phaseolus vulgaris L.) in Central America and the Caribbean are often produced on low fertility soils which reduces crop yield. Bean breeding programs need to identify genotypes that have superior adaptation to these conditions. Objective. Identify Mesoamerican bean germplasm lines with superior adaptation to low soil fertility. Materials and methods. The performance of twenty-seven Mesoamerican bean (Phaseolus vulgaris L.) lines from the Bean Abiotic Stress Evaluation (BASE) 120 panel were evaluated in an unfertilized oxisol at Isabela, Puerto Rico over five growing seasons (four-year period from 2015-2018). The lines were inoculated with a mixture of Rhizobium etli and R. tropici to promote symbiotic nitrogen fixation (SNF). Results. Four lines produced mean seed yields >1,200 kg ha-1 and had estimates of nitrogen derived from the atmosphere (NDFA) >50 %. Greater nodule number was positively correlated with % NDFA, later maturity and seed yield. The heat and drought tolerant small red cultivar ‘Rojo Chortí’ and the heat tolerant white cultivar ‘Verano’ had among the smallest apparent C isotope discrimination values suggesting greater water use efficiency. Among the elite lines in the trial, root rot damage was minimal and the basal root growth angles were intermediate (40-60 %), which favored the uptake of water and soil nutrients. Conclusion. Mesoamerican bean lines with superior seed yield and enhanced symbiotic nitrogen fixation in a low fertility soil were identified. Many of these lines also possess resistance to other biotic and abiotic factors that limit bean seed yield in Central America and the Caribbean.