关键词: 土壤质地, 苹果, 砧木, 根际微生物, 功能多样性, 根际效应

Abstract: Bacterial 16S rRNA gene copy number，bacterial rhizosphere effect，microbial community metabolic activity，functional diversity and carbon source utilization types in rhizosphere and non- rhizosphere soils were analyzed in two-year old potted apple trees（Malus × domestica Borkh.‘Red Fuji’ with Malus robusta Rehd. and Malus hupehensis Rehd. as rootstock）planted in sandy loam，loam and clay loam respectively. Results showed that among all parameters that were tested，three of them including the bacterial copy number，microbial community metabolic activity and functional diversity index displayed the exact same trend. Clay loam had the highest numbers followed by loam and sandy loam. Numbers in M. hupehensis were higher than those in M. robusta. Rhizosphere soil had higher numbers than non-rhizosphere soil. Rhizosphere effects in the 2 rootstocks were the largest in sandy loam and the smallest in clay loam，and the bacterial abundance in sandy loam soil was most affected by rootstocks. The utilization capacity of carbon sources of rhizosphere and non-rhizosphere microbial community in clay loam were the highest followed by loam and sandy loam. The utilization capacity of phenolic acids and carboxylic acids in rhizosphere microbial community was significantly higher than that in non-rhizosphere microbial community. Rhizosphere microbial community of M. robusta had the highest utilization capacity of carboxylic acids in sandy loam and the lowest in clay loam whereas M. hupehensis showed the opposite trends. Types of carbon sources used by rhizosphere microbial community varied with soil texture. In sandy loam，amino acids were mainly used，followed by carbohydrates and carboxylic acids; in loam，carbohydrates were mainly used，followed by polymers and amino acids; and in clay loam polymers were mainly used，followed by amino acids and carbohydrates. The principal component analysis showed that the rhizosphere microbial community types of the two rootstocks were separated by different soil texture types and they were gathered in the same soil texture，which indicated that the type of carbon source utilization of apple rhizosphere microbial community was more susceptible to soil texture，while the difference between the two rootstocks had less impacts.

Key words: soil texture, apple, rootstock, rhizosphere microorganism, functional diversity, rhizosphere effect