A Comparative Analysis of Co-Inoculation of Microbial Biostimulants at Different Irrigation Levels Under Field Conditions on the Cucumber Growth

Abstract

Drought is one of the most important abiotic stress factors that limit plant growth and reduce yield and quality worldwide. Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR), known as microbial biostimulant (MB) promote plant growth in a variety of adverse environmental conditions. The objective of this study was to determine the effects of PGPR and AMF inoculation on cucumber yield, water use efficiency, nutrient content and fruit quality in across two growing seasons and four different irrigation levels (I-1: 33%, I-2: 66%, I-3: 100% and I-4: 133%) under field conditions. While mycorrhizal colonization (MC) and relative mycorrhizal dependence (RMD) increased proportionally with water deficit, single AMF inoculation produced higher MC and RMD rates than co-inoculation. Our results revealed that AMF inoculation at I-4 produced the highest yield (991.46 g plant(-1)), the lowest yield was found in the control group with 294.41 g plant(-1) in I-2 irrigation. AMF and AMF+PGPR inoculation boosted I-1 crop yield more than uninoculated plants on average 66.52% and 33.93%, respectively. At the same time, it was determined that while uninoculated plants experienced more than 40% yield losses in I-1 compared to full irrigation (I-3), MB applications mitigated these losses. The AMF and AMF+PGPR inoculations were more effective in terms of water use efficiency (WUE), with I-1 showing the highest WUE values. Under water deficiency conditions, MB applications increased fruit length, fruit width and fruit firmness compared to uninoculated plants.