Dynamics of germination stimulants dehydrocostus lactone and costunolide in the root exudates and extracts of sunflower

Abstract

Orobanche cumana Wallr. ( Orobanche cernua Loefl.) causes severe yield losses of confectionary sunflower in China. While germination of O. cumana is stimulated by sesquiterpene lactones (STLs) from host sunflower ( Helianthus annuus L.). Dehydrocostus lactone and costunolide isolated from sunflower root exudates are known as STLs to specifically induce O. cumana germination. Two major confectionary sunflower cultivars, SH363 (highly susceptible to O. cumana ) and TH33 (resistant to O. cumana ), were planted in China. However, STLs in these two sunflower cultivars has remained unknown. To identify STLs from root and exudates of sunflower for better understanding the role of stimulants in parasitic interaction of sunflower and O. cumana , we tested dehydrocostus lactone (DCL) and costunolide (CL) in root and root exudates of susceptible and resistant sunflower cultivars. The stimulant activity of sunflower root exudate and root extract to germination of O. cumana were also determined. Dehydrocostus lactone and costunolide were identified through ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS). Both DCL and CL were found in root extracts and root exudates in the whole tested time point from two sunflower cultivars. The concentration of dehydrocostus lactone was higher than that of costunolide at the same tested growth stage of each sunflower cultivar. It was observed that higher quantity of dehydrocostus lactone in susceptible cultivar than resistant cultivar of root and root exudates at later tested developmental stages. However, the amount of CL was no significant difference between SH363 and TH33 at all tested stages. The release amount of DCL from susceptible cultivar is 3.7 folds that of resistant cultivar at 28 DAT. These findings suggested that DCL was the one of the major signal compound in these two sunflower cultivars, and lower dehydrocostus lactone might contribute to the resistance of sunflower TH33 to O. cumana .

First case of evolved herbicide resistance in the holoparasite sunflower broomrape, Orobanche cumana Wallr.

“…Sunflower broomrape is a non-photosynthetic root parasite plant that relies entirely on the host for its nutrients and water ( Fernández-Martínez et al., 2015 ). Chemical control of O. cumana is complicated because it produces a large number of seeds that can survive in the soil for several years and sprout when stimulants from the host roots are detected ( Plaza et al., 2004 ; Wu et al., 2022 ). For effective control of O. cumana , the herbicide must be sprayed at the right growth stage of the sunflower plant so it can be optimally translocated to the host roots and suppress the developing broomrape ( Joel et al., 2007 ).…”

Wild Helianthus species: A reservoir of resistance genes for sustainable pyramidal resistance to broomrape in sunflower

“…After exposure to adequate humidity and temperature conditions, the broomrape tiny seeds perceive germination stimulants (GS) produced by sunflower root exudates and germinate in the proximity of their host roots. Sunflower GS include a cocktail of molecules such as sesquiterpene lactones (for example dehydrocostus lactone-DCL and costunolide; Joël et al., 2011 ; Wu et al., 2022 ) and strigolactones (such as heliolactone, Ueno et al., 2014 ). During the 2 nd stage, once the seeds have germinated, the radicle develops and orientates itself toward the host root by chemotropism ( Krupp et al., 2021 ).…”