The response of rhizosphere microbial properties to flavonoids and Nod factors

Abstract

Flavonoids and Nod factors (lipo-chitooligosaccharides) influence legume growth, plant–microbe communication and regulate microbial community. To assess the effects of pea (Pisum sativum) seed inoculation with flavonoids and Nod factors on microbial parameters, field study was performed on a Haplic Luvisol. Flavonoids were extracted from sprouted pea seeds, and Nod factors were isolated from Rhizobium leguminosarum bv. viciae strain GR09. Pea seeds were soaked with flavonoids (F), Nod factors (Nod), mixture of both compounds (F + Nod) or water (control, C) and then planted. Enzyme activities (dehydrogenases, protease and acid phosphatase), the numbers of cultivable fungi, bacteria, Pseudomonas and Bacillus were determined in pea rhizosphere. Generally, a significant increase was observed in dehydrogenases and protease activities, bacteria, Pseudomonas and Bacillus numbers under F, Nod and F + Nod treatments compared to control and decrease in fungi number. The effect of F and Nod factors was significant for most of the microbial parameters analysed. Significant interactions between F and Nod factors for a number of fungi and Pseudomonas population were found. The results indicate that the application of F and Nod factors on seeds could improve root–microbes interactions through enhanced microbe number and activity in pea rhizosphere.