Optimizing woody oil biodiesel production in yellowhorn via phenotypic marker development: a study of trait–index associations and germplasm screening

The seed oil of yellowhorn (Xanthoceras sorbifolia Bunge) represents a promising feedstock for biodiesel production, but the detection process associated with its quality is both cumbersome and costly. This work focused on early selection of high-quality germplasm to reduce production costs and enhance genetic gains. An analysis of the relationships between 25 quantitative leaf traits and 8 biodiesel characterization indices in yellowhorn at the experimental and demonstration base in Tongliao City, China, identified 5 key leaf functional traits—leaf Soil Plant Analysis Development (SPAD), frond number (FN), leaf rate of water content (LRWC), leaf shape index (LSI), and the wax-to-leaf thickness ratio (W/L)—that showed significant correlations with the biodiesel characterization indices. These traits were identified as critical indicators for predicting biodiesel quality. Furthermore, a predictive map was developed to delineate optimal biodiesel characteristics, encompassing the ranges of SPAD (35.00–49.92), FN (13.17–18.83), LRWC (0.37 %–0.51 %), LSI (0.23–0.40), and W/L (0.01–0.04). The findings of this study provide technical support for employing straightforward and testability traits to forecast complex indicators, thereby facilitating the preliminary selection of high-quality biodiesel yellowhorn germplasm breeding.