Abstract
Most agricultural soils worldwide present limited availability of phosphorus (P) and crops require supplemental application of P fertilizers. Due to the economic and environmental concerns derived from the use of P fertilizers, identifying and breeding P-efficient lettuce (Lactuca sativa L.) cultivars is imperative for the reduction of production costs and implementation of more sustainable practices. Phosphorus use efficiency (PUE) remains unexplored in lettuce. In this research, 66 lettuce genotypes of six morphological types were evaluated between standard recommended P rate (202 kg·ha–1 of P2O5) and half-P rate (101 kg·ha–1 of P2O5). Lettuce genotypes were tested in two field experiments conducted during the 2017-2018 and 2019-2020 growing seasons in the organic soils (Histosols) within the Everglades Agricultural Area of South Florida. Head weight, marketability, tissue P concentration, soil total-P concentration, and soil extractable P were measured. Genetic variation was detected for PUE within romaine, crisphead, butterhead, Latin, and loose leaf. Eight genotypes were found to produce similar or higher head weight and good marketability when grown in the half-P rate compared to the standard P rate. No correlations were detected between head weight and tissue P concentration, indicating possible variation in P uptake and utilization on the tested lettuce genotypes. A significant, positive correlation was observed for soil total-P and soil extractable P, indicating that the increase in total P concentration of Histosols resulted in higher availability of P to plants. Lettuce genetic variation for PUE may allow further development of P-efficient cultivars for conventional and alternative production systems. More comprehensive investigations must be conducted to elucidate the genetic mechanisms controlling PUE in lettuce.
Genetic Variation in Root Architectural Traits in Lactuca and Their Roles in Increasing Phosphorus-Use-Efficiency in Response to Low Phosphorus Availability