Abstract:

【Objective】 Study the effects of AM fungi and nitrogen addition on the root infection rate and photosynthetic characteristics of sorghum，to screen for the optimal amount of biological and nitrogen fertilizer.【Methods】Using pot experiment，6 treatments were set up including 0，150，and 300 kg/hm² three nitrogen levels（N0，N1 and N2） and two AM fungal treatments（inoculation GM and non-inculation NGM）. Sorghum root infection status and photosynthetic indexes at filling stage were investigated.【Results】AM fungi and nitrogen treatments had significant interactions（P<0.05） on sorghum root infection rate，leaf stomatal conductance，and leaf transpiration rate. Compared with the non-inoculation treatment，the sorghum leaf chlorophyll contents of inoculated N0，N1，and N2 levels increased by 10.80%，8.29%，and 8.78%（P<0.05），respectively，and the net assimilation rate increased by 8.86%，9.47%，and 4.03% （P<0.05），respectively. The sorghum leaf transpiration rates of N0 and N1 levels increased by 24.85% and 16.14%，respectively（P<0.05）. Under the inoculation treatment，compared with N0 level，the sorghum root infection rates under N1 and N2 levels decreased by 35.38% and 30.77%，respectively（P<0.05），and the leaf stomatal conductance decreased by 15.96% and 19.54%，respectively（P<0.05）. Correlation analysis showed that AM fungi addition resulted in significant positive correlation of sorghum root infection rate with leaf chlorophyll content，stomatal conductance，net assimilation rate，and transpiration rate（P<0.05）.【Conclusion】AM fungi inoculation and 150 kg/hm² of nitrogen fertilizer addition were the best treatments to reduce root infection rate and improve the photosynthetic characteristics of sorghum.

Key words: AM fungi, Nitrogen, Interaction, Sorghum, Root infection rate, Photosynthetic characteristics