Study On Allelopathic Effects Of Oat Seeds And Seedling Extracts On Weeds

Oat(Avena)is an important annual grain and forage crop in cold region of north China.Field weeds affect oat quality and yield by competing with oat for nutrition,light and space.In the competition with weeds,crops release some allelochemicals that affect the germination and growth of weed seeds.At present,the allelopathic effect of oat has been studied abroad,but it is rarely reported in China.Therefore,5 different oats(diploid Bailv No.1 and Xiaoyoumai,tetraploid ZY003622,hexaploid Longyan No.3 and Baiyan No.2)were used as materials,to study the allelopathic effects of different concentrations of oat seeds and seedling water extracts on 5 species of weeds(Amaranthus retroflexus,Chenopodium glaucum,Amaranthus spinosus,Setaria viridis and Brassica napus).The oat germplasm with strong allelopathic activity was screened,and the allelopathic potential substances contained in it were isolated and identified,provide a theoretical basis for the biological control of weeds in the field.The main results were as follows:(1)The allelopathic effects of different oat seed extract on 5 species of weeds were significantly different.The allelopathic effect of Avena nudibrevis on A.spinosus and S.viridis was strong,and the synthetical allelopathic effect was-0.73 and-0.78;the synthetical allelopathic effect of Longyan No.3 on A.spinosus and B.napus was-0.80 and-0.81,respectively.Other test materials had weak allelopathic activity.When Longyan No.3 seed extract concentration was above 80mg/m L,the inhibition on the germination rate,seed germination rate index and root length of B.napus increased with the increase of concentration,at the concentration of 320 mg/m L,the allelopathic effect indices were-0.98,-0.99 and-0.84,respectively.The growth of B.napus shoots were promoted at concentrations of 80 mg/m L and 160 mg/m L,and was inhibited at 320 mg/m L.(2)The synthetical allelopathic effects of tested oat seedlings water extract on 5 species of weeds were all negative,showing different degrees of inhibition.Allelopathic effect indices of Bailv No.1 on A.spinosus,B.napus and S.viridis were-0.85,-0.96 and-0.81,respectively.Baiyan No.2 had the strongest allelopathic activity on A.retroflexus,but the weakest on B.napus.At the concentration of 60 mg/m L and above,the Bailv No.1 seedling water extract increased the germination rate,seed germination speed index,root length and shoot length of B.napus,and the allelopathic effect index at 100 mg/m L was-0.96,-0.98,-0.98 and-0.90,respectively.(3)Organic solvents of different polarity were selected for extraction and separation of allelopathic potential substances in Longyan No.3 seed and Bailv No.1 seedling extract with strong allelopathic activity.Bioactivity assay results showed that the n-butanol extracts of both materials had the strongest allelopathic activity on B.napus,and the inhibitory effect increased with the increase of concentration,synthetical allelopathic effect at 1.0 mg/m L was-0.74 and-0.75,respectively.Using LC-MS technology,32 compounds were identified in the n-butanol extract of Longyan No.3 seed water extract,and 25 compounds were identified in Bailu No.1 seedlings water extract.(4)Among the 11 oat allelopathic potential substances,coumarin and cinnamic acid significantly inhibited the germination rate and germination speed index of B.napus,and increased with the increase of extract concentration,the comprehensive effect indices at 0.20 mg/m L were-0.65 and-0.84,respectively.Scopoletin was toxic to B.napus,and the toxicity is enhanced with increasing concentration.All of the 11 substances can inhibit root growth,and had different effects on shoot length.Ferulic acid,caffeic acid and palmitoleic acid promoted B.napus shoot growth,syringic acid,DL-tryptophan,2,4-dihydroxybenzoic acid,vanilla acid and isovanilla acid showed low concentration promotion and high concentration inhibition on B.napus shoot growth.