A Strategic Breeding Approach for Improvement of a Native Greek Chamomile ( Matricaria chamomilla L.) Population for High-Yield and Optimized Chemical Profile Under Mediterranean Low-Input Conditions

Chamomile ( Matricaria chamomilla L.) is a popular herb of great economic and medicinal value. Despite its significant potential, there are currently no commercially available varieties specifically adapted to Mediterranean low-input farming systems. The present study aimed to develop a genetically improved breeding population derived from indigenous Greek chamomile germplasm, following a multi-year strategy, based on pedigree selection under low-input conditions. This selection process constituted the first phase of the breeding program, during which selection focused on improving inflorescence dry weight and essential oil quality, particularly with respect to α-bisabolol and chamazulene content. After three cycles of selection, considerable genetic gains were achieved. The realized heritability values exceeded 0.5 for all assessed traits, confirming strong genetic control. In the fourth year, representing the second phase of the breeding program, the breeding population—developed through selection during the first phase—was evaluated alongside the initial population and commercial diploid and tetraploid varieties. The breeding population exhibited significant observed gains compared to the initial population: inflorescence dry weight increased by 12.17%, α-bisabolol content by 71.45%, and chamazulene content by 6.57%. Additionally, the breeding population not only surpassed all evaluated diploid genotypes in essential oil composition, but also displayed a chemotypic shift, indicating successful alignment with tetraploid varieties characterized by high-value chemical profiles. Furthermore, this selection process targeting specific commercial chamomile traits indirectly contributed to improvement in plant height and inflorescence morphology. Overall, these results demonstrate that conventional breeding, when applied effectively to native resources, can enhance both agronomic performance and essential oil profile. The newly developed breeding population provides a strong foundation for future cultivar development tailored to Mediterranean low-input sustainable farming systems.