翻译：苹果是全球重要的水果之一树龄偏高造成的树势衰弱严重影响苹果产量和品质。ACC脱氨酶是参与乙烯代谢的重要酶为了明确苹果根内具ACC脱氨酶和解磷功能内生细菌的生物学效应本研究采用从苹果树根中筛选鉴定具ACC脱氨酶和解磷活性高的假单胞菌菌株室内发酵后施用于树龄16年苹果树田间试验研究其对对苹果产量、品质的影响及对土壤的生态效应和苹果根系内生细菌群落结构的影响试验结果如下：经形态学鉴定和基于16Sr

Translation: Apple is one of the important fruits globally, but due to the high age of the trees, the weakened tree vigor seriously affects the apple yield and quality. ACC deaminase is an important enzyme involved in ethylene metabolism. In order to clarify the biological effects of ACC deaminase and phosphorus-solubilizing endophytic bacteria in apple roots, this study screened and identified Pseudomonas gessardii (strain PG-9) with high ACC deaminase and phosphorus-solubilizing activities from the roots of apple trees. After indoor fermentation, it was applied to 16-year-old apple trees in field experiments to study its effects on apple yield, quality, soil ecological effects, and the community structure of endophytic bacteria in apple roots. The results of the experiment are as follows: Through morphological identification and comparative analysis of the 16SrRNA gene sequence and phylogenetic analysis, strain PG-9 was identified as Pseudomonas gessardii, with a GenBank accession number of OP236515. Field experiments conducted from 2021 to 2022 showed that in terms of yield, the average fruit quality and yield per hectare of the treatment group increased by 7.82% and 7.1% and 9.28% and 8.24% respectively compared to the control. In terms of quality, the titratable acid content decreased by 29.17% and 34.78% compared to the control over the two years, while the soluble sugar content increased by 15.40% and 30.41%, with significant differences compared to the control. The available phosphorus content in the apple rhizosphere soil treated with strain PG-9 was 8.72% higher than the control, while the total phosphorus content was 11.38% lower than the control. Compared to the control, strain PG-9 changed the microbial community structure in the soil, increased the number of bacterial species, and decreased the number of fungal species. After 2 years of treatment with strain PG-9, the number of endophytic bacterial species in apple roots decreased, but there was no significant change in Alpha diversity (P>0.05), and the relative abundance of dominant bacterial taxa in apple roots was altered