Pseudomonas chlororaphis and organic amendments controlling Pythium infection in tomato

Joeke Postma,Els H Nijhuis

doi:10.1007/s10658-019-01743-w

Abstract

To create more resilient growing systems for greenhouse crops, the efficacy of different organic amendments alone and in combination with the biocontrol strain Pseudomonas chlororaphis 4.4.1 was tested to suppress Pythium disease in tomato plants. Four independent greenhouse experiments were performed with young tomato plants in potting soil. Inoculating the pathogen Pythium aphanidermatum to the potting soil prior to sowing resulted in significant losses of tomato plants; i.e. 94–98% healthy plants in pathogen-free control compared to 43–68% healthy plants when the pathogen was added. P. chlororaphis 4.4.1 inoculations increased the number of healthy plants in the potting soil up to 80% on average; soil and seed treatment were both effective. Numbers of P. chlororaphis in the rhizosphere had increased 4 to 100 fold 3 weeks after its inoculation (qPCR detection). All compost types reduced Pythium disease in potting soil resulting in 80–95% healthy plants. Animal bone char was not effective against P. aphanidermatum, whereas with plant-based biochar there was an effect, although not significantly different from the control treatment. Phosphorous and potassium uptake by the plants were elevated by the different organic amendments. These results demonstrate the potential of the organic amendments to enhance sustainability of growing media such as potting soil by increasing its disease suppressiveness, the re-use of nutrients and replacement of peat by using organic amendments. In addition, inoculating the growing medium or tomato seeds with the biocontrol strain P. chlororaphis 4.4.1 enhanced Pythium control in the susceptible growing media.

Highlights

With an increasing world population (predicted 9.7 × 109 in 2050 (United Nations 2017)) and a growing need for food, agricultural systems must become more productive and more sustainable
The applied dosages of the organic amendments did not significantly influence germination of the seeds; except for two compost batches in the 2014 experiment COSPBS and COSPBD that seriously reduced seed germination, i.e. germination rates were 68 and 73% respectively. These composts were prepared from green waste with manure for fertilizer purpose and appeared to be phytotoxic when added in a 10% dosage to potting soil
Several types of compost and two biochars were mixed with potting soil in four independent greenhouse experiments

Summary

Introduction

With an increasing world population (predicted 9.7 × 109 in 2050 (United Nations 2017)) and a growing need for food, agricultural systems must become more productive and more sustainable. Organic materials are treated as waste, but have the potential to be re-used as fertilizer, as soil improver or as part of growing media In this context, the paradigmatic shift in waste management initiated by the European Waste Framework Directive (Council Directive 2008/98/EC) enhances the possibility of continuing the life cycle of materials in the perspective of a circular economy, i.e. organic rich waste can be applied for agricultural beneficial use allowing organic matter and nutrient cycling, as alternatives to their landfilling or incineration (Alvarenga et al 2017; Estrada De Luis and Gómez Palacios 2013; Manfredi and Pant 2013). A wide range of resources and products with the potential to overcome soil constraints, improve nutrient use efficiency or support plant health, is available for application in agriculture (Abbott et al 2018)

Methods

Results

Conclusion