Effect of polymer film on plant-pathogen interactions: a case study on damping-off caused by pythium irregulare in field peas (Pisum sativum)

The use of Clear Polymer Film (CPF) for field crops improves crop establishment via increased soil and air temperature, and the capture and recycling of CO₂ and water vapour. However, little is known about how CPF affects soil borne diseases. We developed a case study with Pythium irregulare which is a common seedling pathogen affecting field pea (Pisum sativum). An experiment was designed using CPF-enclosed (5 cm headspace) and ambient chambers filled with potting soil, where pea seedlings (Greenfeast cultivar) were either inoculated with P. irregulare or not. As expected, CPF increased the maximum temperature in both treatments and resulted in faster emergence than the ambient chambers. Plant height, and number of fully expanded leaves were significantly higher (P<0.05) for plants grown in the CPF chambers. Inoculation with the pathogen led to significantly lower plant height and number of leaves for plants grown in the ambient chambers but not for those in the CPF chambers. The pathogen was re-isolated more frequently from roots of plants that were grown in ambient conditions. The study concluded that CPF decreased the impact of P. irregulare infection in GreenFeast pea during these experimental conditions. Field trials would be necessary to determine if these effects could be replicated in a crop environment with natural levels of inoculum. The success of CPF to reduce root infection is likely related to the optimal soil temperature required for both the plant and pathogen, and in this case the increased soil temperature may have been less favourable for pathogen growth relative to pea growth.