Diversity and dose-dependent allelopathic potential of volatile sesquiterpenes from root extracts of Chrysanthemum morifolium cultivars

Chrysanthemum x morifolium Ramat. (chrysanthemum) is rich in terpenoids in both aboveground and belowground parts with multiple biological functions. This study aims to comprehensively assess the diversity of rootderived terpenoids and their potential role in plant-plant interaction in chrysanthemums. By GC-MS identification, we revealed the intraspecific variation of terpenoid components dominated by sesquiterpenes in the root extracts among 26 chrysanthemum cultivars with different application types (including cut-flower, ground-cover and tea cultivars). The total terpenoid content in tea cultivars was generally higher than that in ground-cover and cut-flower cultivars. In this context, the correlation between the terpenoids from root extracts and allelopathic effect was established. The root extract of tea, cut-flower and ground-cover cultivars could universally promote the root length of Lactuca sativa seedling without significant effect on bud length. Moreover, the root extracts of tea and cut-flower cultivars showed no significant effects on the bud length and root length of Echinochloa crusgalli seedlings, whereas the root extract of ground-cover cultivars could significantly promote the bud length and inhibit the root length of E. crus-galli seedlings. OPLS analysis successfully correlated the content of sesquiterpenes (ll-farnesene, ll-elemene, ll-bisabolene, neollocimene, ll-sesquiphellandrene and a-longipinene) with bud and root length of L. sativa and E. crus-galli seedlings. Additionally, root extracts of 3 representative cultivars in each application type displayed dose-dependent effect in the seed germination of L. sativa. These findings provide a scientific basis for the development of eco-friendly herbicides\plant growth regulator and the arrangement of reasonable farming systems in chrysanthemum.