Epsilon Archive for Student Projects

Abstract

The use of biocontrol agents with plant growh promoting activity has emerged as one of the approaches to support sustainable agriculture. From our previous field evaluation, four out of six rhizobacteria with biocontrol activity had a direct positive effect on potato plant height. This study aims to explore their growth promoting activity on tomato and potato plants and the possible molecular mechanisms involved. Four strains, Pseudomonas fluorescens 121, Serratia plymuthica S412, Serratia rubidaea 268, and S. rubidaea 119, were tested for growth promoting activity on tomato and potato plants grown in vitro and in pot experiments. The changes in the expression level of auxin-related genes were investigated. Under in vitro condition, 121 and 119 stimulated adventitious root development in the aerial plant part and shoot growth of potato. Meanwhile, growth promotion activity on in vitro grown tomato could not be observed due to technical issues such as seed contamination, ununiform seed germination and inconsistent results.
Inoculation with P. fluorescens 121 and S. rubidaea 119 altered the expression levels of selected auxin-related genes. P. fluorescens 121 transcriptionally upregulated StPIN1 in the root, StPIN5 in the shoot and StLAX5 and StPIN6 in both plant parts but downregulated StPIN6 in the root. Meanwhile, S. rubidaea 119 transcriptionally upregulated StPIN1 in the root, StLAX5 in the shoot and StPIN5 in both plant parts. These results suggest that both rhizobacteria enhanced polar auxin transport in the root and auxin homeostasis in both plant parts. In the pot experiment, potato plants with rhizobacteria applications showed higher yield and total dry weight than non-inoculated plants. In tomato, 121-treated plants had higher yield, plant height, total dry weight, number of leaves and chlorophyll content than other treatments. This study suggests that all rhizobacteria can be plant growth promoting rhizobacteria (PGPR) for potato, and P. fluorescens 121 exerts the best growth promoting effects on both crops.