Metabolomic and transcriptomic analyses provide insight into the variation of floral scent and molecular regulation in different cultivars and flower development of Curcuma alismatifolia

Curcuma alismatifolia is an important ornamental plant of significant economic value, while the floral fragrance has been rarely investigated, leading to a lack of knowledge about the floral scent. By performing metabolomic and transcriptomic analyses, we investigated the variation of 906 volatile organic compounds (VOCs) in florets of eight C. alismatifolia cultivars and four different developmental stages of "Chiang Mai Pink" (CMP). The metabolite profiling revealed that the terpenoid group (213 out of 906) was the predominant VOC, accounting for 33.5% and 43.4% of total VOC contents in the florets of different cultivars and developmental stages, respectively. Sweet and woody were the predominant odors not only in different cultivars but also during developmental stages. The varied intensities of other odors contributed to forming odor diversities in C. alismatifolia floret. We uncovered seven terpenoid synthetase (TPS) genes and four MYB genes of significant association with the biosynthesis of terpenoids in eight cultivars and floret development, respectively. We performed an activity assay on four selected TPS genes and identified that Chr15HA1352 and Chr15HA2528 are responsible for the biosynthesis of alpha-farnesene. The significant association between the MYB gene (Chr03HA28) and seven terpenoids can be observed among different cultivars and during different developmental stages. These findings highlight the varying floral scents in different cultivars and floret development and suggest the potential roles of identified TPS and MYB genes in the biosynthesis of terpenoids in C. alismatifolia.