Progeny Differentiation in Faba Bean Using Hyperspectral Images and Machine Learning

Though currently a minor crop, faba bean is a promising source of plant-based protein as global diets shift towards more plant-based nutrition. To realize this potential, advances in breeding and cultivation are crucial. To exploit heterosis, faba bean breeding frequently utilizes synthetic cultivars, produced by open pollination of inbred lines, resulting in a mixture of F₁ hybrid seeds and self-pollinated offspring. Pure F₁ hybrid cultivars are currently unavailable due to unstable cytoplasmic male sterility (CMS) systems. An ability to distinguish F₁ seeds from their parental inbreds based on characteristics associated with the xenia effect could change this. The xenia effect refers to the influence of paternal pollen on seed traits, for example, seed weight and cotyledon cells in faba bean. In this study, we exploited the xenia effect captured in hyperspectral imaging data to develop machine learning scenarios for discriminating between parental and F₁ seeds of open-pollinated synthetic combinations (Syn-1). The hyperspectral data were preprocessed using Savitzky-Golay filtering to reduce noise and smooth the spectra. Various machine learning algorithms were applied, incorporating Bayesian hyperparameter optimization. The scenarios achieved up to 98.9% accuracy in separating parental components of Syn-1. When including all seeds, the model achieved an F₁ score of 40.7%, indicating moderate detection and classification performance. As the harmonic mean of precision and recall, the F₁ score reflects both the correctness of F₁ seed identifications and the completeness with which F₁ seeds were identified. While this approach does not yet enable the development of full hybrid cultivars, it paves the way for hybrid-enriched cultivars. These could help to streamline breeding for synthetic cultivars and potentially increase yields, for example, by increasing the proportion of F₁ hybrid seeds in synthetic cultivars. This study extends knowledge of the xenia effect in faba bean and provides a basis for further research aimed at enhancing breeding methods and productivity.