Abstract:
Objectives Rhizosphere growth-promoting bacteria of pear trees and their associated biostimulants, which have synergistic effects with bacteria, were screened in our study to examine the combined effects of bacteria and biostimulants on the yield and quality of pear fruits.
Methods Based on the characteristics of 128 rhizosphere bacteria, including phosphate solubilization, potassium release, and nitrogen fixation, isolates with strong growth-promoting effects on pear seedlings were screened. Meanwhile, biostimulants that significantly enhance the growth of pear seedlings, such as alginate oligosaccharides (AOS), 5-aminolevulinic acid (5-ALA), and gamma-aminobutyric acid (GABA), were also selected. The effects of bacteria alone or in combination with biostimulants on the growth of pear trees and the yield and quality of pear fruits were investigated.
Results An isolate (Pseudomonas CD1) which significantly enhances the growth of pear trees, was identified. Additionally, AOS was identified as an efficient biostimulant. Compared to the control (CK), CD1 alone, and AOS alone, the combination of CD1 and AOS significantly enhanced the growth and lateral root initiation of pear seedlings, increasing biomass by 158.8%, 59.0%, and 46.7%, respectively. The total root length increased by 33.7%, 23.2%, and 26.3%, respectively, compared to CK, CD1 and AOS. Furthermore, this combination significantly promoted the growth and yield of pear fruits, increasing by 73.7%, 10.0%, and 14.8%, respectively, and soluble sugar content increased by 64.2%, 29.0%, and 61.8%, respectively, compared to CK, CD1, and AOS treatments. Meanwhile, the stone cell content in the combination treatment was significantly decreased by 63.6% and 43.1% compared to CK and AOS treatments, significantly improving fruit quality. The combination also increased fruit biomass by 52.8%.The N, P, K, Ca, Mg, Cu, Zn, and B mineral contents in the fruit were increased to varying degrees compared to CK, CD1 alone, and AOS alone, leading to a significant accumulation of mineral elements in the fruit.
Conclusions AOS and Pseudomonas CD1 exhibited synergistic effects in promoting the yield and quality of pear fruits. However, their mechanism requires further study in the future.