Importance and causal agents of root rot on field pea and lentil on the Canadian prairies, 2014–2017

Citation

Chatterton, S., Harding, M.W., Bowness, R., Mclaren, D.L., Banniza, S., Gossen, B.D. (2019). Importance and causal agents of root rot on field pea and lentil on the Canadian prairies, 2014–2017, 41(1), 98-114. http://dx.doi.org/10.1080/07060661.2018.1547792

Plain language summary

Root rots of peas and lentils have been increasing on the Canadian Prairies recently. Several pathogenic microorganisms can cause root rots, and it was unknown which organisms were mainly responsible. It can be difficult to detect and distinguish microorganisms from each other. Therefore, use of DNA barcodes that are specific to organisms of interest were used to identify pathogens present in the roots. Surveys were conducted from 2014 - 2017 to determine how frequent and how severe root rots are in pea and lentil crops, and to also determine the most important pathogenic microorganisms. Root rots were present in every field surveyed, with moderate severity. Root rot severity tended to be higher in wetter years, and lower in drier years, and this was especially true for lentils. One pathogen, Aphanomyces euteiches, that was only recently found in Alberta and Saskatchewan, was widespread and caused the most damage to pea and lentil crops. However, other pathogens were almost always present at the same time as Aphanomyces. This study identified the major pathogens that are impacting production of pea and lentil crops in the Prairies and highlights that surveys with diagnostic components should be performed regularly to document important changes in pathogen composition. This information is now being used to research disease management strategies and development of programs to breed for resistance to the major pathogens.

Abstract

© 2018, © 2018 Her Majesty the Queen in Right of Canada, as represented by Agriculture and Agri-Food Canada (AAFC). Surveys of pulse crops across the Canadian prairies were undertaken between 2014 and 2017 to assess the distribution and severity of root rot of field pea and lentil, to identify the most important causal agents, and to compare the efficiency of culturing techniques with multiplex PCR. Root rot was present in every pea and lentil field surveyed in all three provinces. When assessed based on province and soil zone, moderate to severe symptoms (severity > 3 on a 1–7 scale) occurred in 25–99% of pea fields, but only 8–34% of lentil fields. Root rot severity on both crops was higher in growing seasons with high precipitation and was lower in drier years, but only lentil showed any difference associated with soil zone, with lower severity in the brown soil zone. This study demonstrated that Aphanomyces euteiches occurs across the Prairie region, where it caused moderate to severe injury on many field pea crops. Fusarium avenaceum was the most common pathogen identified in both culturing and PCR analyses, but other Fusarium spp., together with Pythium spp. and Rhizoctonia solani, were also components of the complex. Use of PCR for pathogen identification routinely resulted in identification of many pathogens from an infected root, whereas culturing and isolation resulted in only one or two pathogens per root. PCR was extremely important for assessing the impact of A. euteiches, which was almost never identified using culturing approaches. This observation explains why A. euteiches was not initially recognized as an important pathogen of pulses in the region.