Induction Of DIMBOA And MBOA By Wheat Seedlings Grown In Proximity To Wild Oat (Avena Fatua L.) And Flixweed Tansymustard (Descuminia Sophia L.)

The chemical interactions between the plants-plants, plants-microbes and plants secondary metabolites and pests wounds are induced by secondary metabolites, which are the natural treasure of biologically active chemicals, most of which have been well recognized as allelochemicals. Crop plants have the capability to produce and exude allelochemicals into their surroundings to suppress the germination and growth of weeds in their vicinity. This phenomenon among crop plants as a biological means for integrated weed management was known as allelopathy, which is identified as a category of active agents in the study on chemical ecology.These secondary metabolites as one of crop plants natural defense systems against pests, diseases and weeds have been the subject of numerous studies. The allelochemicals 2,4-dihydroxy-7-methoxy^-1,4-benzoxazin-3-one (DIMBOA) and 6-methoxy-benzoxazolin-2-one (MBOA) in wheat are considered to have a role in the plant's activity against weeds. In this work, we explored the effect of proximity to two weeds, wild oat (Avena fatua L.) and flixweed tansymustard (Descuminia sophia L.), on DIMBOA/MBOA production in wheat seedlings under hydroponic culture to identify whether the breeding of modern wheat varieties with higher concentrations of these compounds could ensure plant-mediated weed control. The main results are follows:1. A method for the determination of DIMBOA/MBOA in methanol was estimated based on ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). The concentrations of DIMBOA/MBOA were analyzed by UPLC-MS/MS under multiple-reaction monitoring (MRM) mode. The qualitative results were obtained based on retention time, the precursor ion and two daughter ions, the quantitative results were on the intention of the characteristic m/z 212.2>194 ion and m/z 212.2>166 ion for DIMBOA, and m/z 166>110 ion and m/z 166>95 ion for MBOA. Limit of quantification of DIMBOA was 0.016 mg L^-1 and MBOA was 0.005 mg L^-1. The method is suitable for the routine and confirmation analysis.2. We quantified DIMBOA/MBOA of 2 tesed wheat seedling (Lumai 168 and Nongda 211) roots exudation in the hydroponic solution using UPLC-MS/MS, MBOA was found and DIMBOA was not detected. The MBOA concentration varied greatly with cultivars, Lumai 168 produced considerable amounts of MBOA; After wheat seedlings were transplanted hydroponically, through the study of daily dynamic change of DIMBOA/MBOA concentration, the more accurate MBOA concentration was got by sampled every day, and the best time to analyze MBOA concentration in hydroponic solution was determined to be the 6th day.3. In wild oat and flixweed tansymustard as biotic stress experiments, MBOA was detected and was noted to exert a significant effect; its concentration in roots of some wheat seedlings was significantly increased irrespective of whether the roots were in contact with or separated from those of the weeds. The weeds were a source of biotic stress to wheat when grown in proximity to it, and the stress resulted in production of higher levels of MBOA in wheat seedlings, although its concentration varied with the wheat cultivar. Therefore, the synthesis and exudation of DIMBOA/MBOA in wheat seedlings appears to be an active metabolic process influenced by the environment, particularly the presence of weeds.