From breeding trait to farm gate: Bean seed quality in Uganda

Abstract

Poor quality seed represents a constraint on introducing favorable traits to farmers and consumers. The bean seed system in Uganda comprises three subsystems: informal (dominated by purchases from grain markets); semiformal Quality-Declared Seed (QDS) from farmer groups; and formal / certified seed. We don’t know how seed quality varies across these subsystems, nor at which step(s) problems may occur. We assess dimensions of seed quality for three biofortified bean varieties at different stages in the Ugandan bean seed system. Working with the regulator, we collected 419 samples from different seed system stages (foundation, production, aggregation, distribution). Regulatory audits were augmented with DNA fingerprinting (DArTag genotyping) and assays for estimating iron and zinc concentration. We compared results from raw samples to samples that had been sorted using visual cues (color, shape, size) designed to mimic farmer seed processing behavior. Results indicate that seed quality loss begins immediately and persists systemwide, with QDS performing the best of the three subsystems. The modest improvement in genetic purity (+3%) achieved by visual sorting confirms that it is inadequate as a substitute for a functioning quality control system. Most biofortified seed samples fell far below the iron and zinc breeding targets (only 25% and 0.3% succeeded, respectively), a result that is independent of genetic purity, revealing a fundamental weakness in the breeding and/or seed multiplication processes. The study recommends overhauling the certified seed distribution through more effective regulation, quality assurance/quality control; further expansion of QDS and reappraising bean biofortification breeding approaches.