Effects of nutrient solution strength, PGPB, and mycorrhizal inoculation on growth,yield, and quality of strawberry
Masoud Haghshenas, S.H. van Delden, Mohammad Javad Nazarideljou
Abstract
Strawberry (Fragaria × ananassa Duch) cultivation is not without difficulty since its root environment is sensitive to many biotic and abiotic stresses. In addition, production is often phosphate limited, even at relatively high phosphorus levels, as the high fruit yields greatly exceed the capacity of the phosphorus supply by the root system. Arbuscular mycorrhizal fungi (AMF), plant growth promoting bacteria (PGPB), and combinations of both are known to mitigate stress and enhance nutrient uptake, particularly phosphorus. Therefore, we studied the effects of AMF (Glomus mosseae, and Glomus intraradices), PGPB (Azospirillum lipoferum DSM1691, and Pseudomonas fluorescens DSM 50090), and their combinations in a greenhouse under either optimal conditions, i.e. electrical conductivity (EC 1.3 dS.m–1), or high nutrient solution strength, i.e. controlled stress (EC 1.9 dS.m–1) conditions. Under optimal EC (1.3 dS.m–1), AMF inoculation increased leaf phosphorus concentrations up to 25% and fruit yield up to 21%. Quality parameters like total phenolic, vitamin C, anthocyanin, fruit EC, and pH were also significantly increased. The high nutrient levels (EC 1.9 dS.m–1) did increase leaf phosphorus but decreased leaf fresh weight (29%) and fruit yield (18%). Substrate inoculation with AMF partly mitigated the stress effect at 1.9 dS.m–1; the plants appeared to be healthier, and the stress indicators – peroxidase activity (POD) and ion leakage – were reduced by AMF. Additionally, AMF inoculation at 1.9 dS.m–1 increased stomatal conductance, relative water content (RWC), chlorophyll index, fruit EC, leaf potassium, and leaf phosphate levels. Plants inoculated with PGPB did not show biologically relevant effects. In conclusion, AMF inoculation has a significantly beneficial effect on fruit yield and quality of substrate-cultured strawberries. These findings can assist growers in further boosting the trend of sustainable agriculture using microbial inoculants, even under optimal conditions of high-tech greenhouses and vertical farms.