香豆素对苜蓿生长的自毒效应分析及其降解菌筛选与鉴定OA

To address the continuous cropping obstacles in alfalfa caused by autotoxic compounds such as coumarin,the coumarin content in alfalfa plants of different ages and their rhizosphere soil was measured using high performance liquid chromatography(HPLC)and their autotoxic effect was eval-uated.Coumarin was also used as the sole carbon source to isolate coumarin-degrading strains from the rhizosphere soil,which were subsequently identified based on their 16S rDNA gene sequence.The physiological and biochemical characteristics of the isolated strains were further analyzed using differ-ent selective media.The results showed that with the increase of growth years,the coumarin concen-tration in both alfalfa plants and rhizosphere soil significantly increased,peaking at 227.31 μg/g and 3.21 μg/g,respectively.Moreover,increasing coumarin concentrations from 0 to 500 μg/mL signifi-cantly inhibited seed germination potential as well as radicle and hypocotyl growth.At 1 μg/mL,the elongation of radicles and hypocotyls decreased by 36.49%and 7.91%,respectively.When the concen-tration exceeded 10 μg/mL,seed germination potential dropped to zero,with all changes being statisti-cally significant.Through screening,one highly efficient coumarin-degrading strain was obtained and identified as Pseudomonas putida,with a maximum degradation rate approaching 100%.Functional analysis indicated that this strain possessed multiple plant growth-promoting traits,including phos-phorus solubilization,potassium release,nitrogen fixation,and ACC deaminase secretion.This study demonstrated that continuous alfalfa cropping leads to the gradual accumulation of coumarin in the soil,which severely impairs seed germination and seedling growth.Pseudomonas putida has strong coumarin degradation capacity and environmental adaptability,providing strain resources and theoreti-cal basis for the microbial control of allelochemicals in the future.