Contrasting germination behavior of nodding broomrape towards soybean seeds- and sprouts-extract is associated with their corresponding phytohormones, sugars and isoflavones contents

Abstract

In the present study, a comparative study involving soybean (Glycine max L.) seeds- (SPE) and sprouts-extract (SSE) as a pre-conditioning media was performed to evaluate their allelopathic impact on nodding broomrape (Orobanche cernua L.) germination. Contrasting germination behaviour of broomrape, characterised by respective inhibition and induction in its germination was observed in response to an optimised concentration of SPE and SSE. Further study was conducted to explore the phyto-constituents of soybean seed- (SSP) and sprout-flour (SSF) responsible for differential germination of broomrape. Plant-growth regulators quantification revealed a relative enhanced bioactive gibberellin (GA₄) to abscisic acid (ABA) ratio (GA₄: ABA) in SSF. Carbohydrates analysis revealed a relative reduced content of soluble-sugars, starch, sucrose (SUC) and raffinose-family oligosaccharides (RFOs) in concomitant with relative enhanced levels of reducing-sugars, glucose (GLU) and galactose (GAL) in SSF. The isoflavone content (IFC) analysis revealed a relative enhanced level of total IFC and individual bioactive aglycones [viz. daidzein, glycitein and genistein (GEN)] in SSF. Exogenous applications of GA₃, ABA and its antagonists (viz. uniconazole and fluridone), mono- (viz. GLU and GAL), oligo-saccharides (viz. SUC and RFOs), SPE₅₀ and SSE₅₀ pre-treated with enzyme-mix harbouring RFOs- and SUC-metabolizing enzymes (viz. α-galactosidase + invertase) and GEN as a pre-conditioning media of broomrape were also in agreement with the aforesaid observations. To the best of our knowledge, this is first report mentioning the contrasting germination behavior of broomrape towards SPE and SSE. Overall, these findings could be explored to formulate the ‘Green’ methods for the control of parasitic-weed infestation in agonomically important crops.