Stem photosynthesis from wild Prunus arabica enhances growth, advances bloom and increases yield in cultivated almond

Rising winter temperatures threaten deciduous fruit tree productivity by depleting carbohydrate reserves during dormancy. This study investigated Stem Photosynthetic Capacity (SPC), a rare adaptive trait from wild Prunus arabica, as a mechanism to enhance almond carbon economy. Using extreme segregating groups from the F1 population (P. dulcis X P. arabica), we evaluated physiological performance through high-resolution lysimetric and multi-year orchard monitoring. High-SPC [SPC(+)] genotypes maintained significantly greater stem CO2 assimilation and transpiration during leafless periods compared to low-SPC [SPC(-)] progenies. Over five successive seasons, SPC(+) trees exhibited a 33.3% increase in trunk secondary growth and reached 10% bloom approximately 8 days earlier. Most importantly, the SPC(+) group achieved a 4.6-fold increase in mean kernel yield when compared to SPC(-) group. These findings demonstrate that SPC provides a flexible, supplementary winter carbon source that directly supports both vegetative and reproductive development. Integrating SPC into commercial almond breeding programs may offer a valuable strategy to improve climate resilience and help sustain yields under warming conditions. HighlightIntegrating stem photosynthesis into commercial almond hybrids provides a winter carbon source that advances blooming, expands trunk growth by [~]33%, and increases kernel yields by more than 4.5-fold.