Medicinal and aromatic plants in the omics era: application of plant breeding and biotechnology for plant secondary metabolite production

Human being has strong and historic connections with plants to fulfill food, feed, and shelter. Moreover, human uses plants as medicine for the treatment of various diseases. Plants are chemical factories for the biosynthesis of the huge number of secondary metabolites (SMs) that are directly used as a medicine or indirectly used in the development of commercial pharmaceutical drugs. Their improvement through classical breeding remains a difficult struggle for plant breeders. Hence, rapidly advancing research on the plant omics era has accelerated our understanding of the complex structure of SMs synthesis in medicinal and aromatic plants (MAPs). In addition, sequencing technologies and the completion of several genome sequences of MAPs have opened numerous opportunities for fine mapping and gene characterization. The accessibility of these technologies together with research of quantitative trait loci (QTL) and candidate genes for key characteristics such as SMs content and biologic activity and resistance to biotic and abiotic stresses pave the way for the development of new strategies for the improvement of MAPs. To explore the knowledge of SMs in MAPs, several reviews have been published over the last three decades for researchers with advanced knowledge of plant biotechnology. However, this review has offered a summary of the recent developments, limitations, and future potential in molecular breeding of MAPs species and their application to plant breeding.