New cyst nematode threats to cereals in the UK (PhD)

Summary

Sector:
Cereals & Oilseeds
Project code:
SR13
Date:
01 January 2006 - 31 December 2008
Funders:
AHDB Cereals & Oilseeds.
Project leader:
Samantha Mitchinson Nematode Interactions Unit, Rothamsted Research, Harpenden, Hertfordshire

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About this project

ABSTRACT

For the past 35 years cereal cyst nematodes (CCN) have been a minor problem in intensive cereal production in the UK and other areas of northern Europe, despite the susceptibility of most cereal cultivars to these widespread pests. Historically, the principal cereal cyst nematode, Heterodera avenae has been controlled by parasitic fungi that destroy the females and eggs of the nematode. This is an example of natural pest control in an intensive agriculture system. In nematode surveys conducted at Rothamsted Research the cereal cyst nematode, Heterodera filipjevi was found in fields in Essex and in Wales. This pest had not previously been recorded in the UK. The research project described aimed to assess the risk of H. filipjevi to intensive cereal production in the UK.

CCN populations were more diverse than expected. In a survey of cereal fields in the UK 65% were infested with CCNs and H. filipjevi was widespread. Heterodera pratensis was also present at one site but studies confirmed that most fields contained mixed populations of H. avenae and H. filipjevi. All CCN populations were suppressed by parasitic fungi that destroyed nematode females and eggs. Cyst nematode populations containing H. filipjevi only produced a single generation in a growing season and their ability to multiply on wheat was similar to that of H. avenae, which also has a single generation. Nematode females and eggs in all populations were parasitised by fungi including Catenaria auxiliaris and Pochonia chlamydosporia (also known to infect H. avenae). Results indicated that these fungi were major factors in limiting nematode reproduction on susceptible crops. The principal CCN pests had different responses to some plant defence compounds. DIBOA a hydroxamic acid produced by wheat and rye as a plant defence compound reduced the hatch and mobility of juveniles of H.avenae and increased their mortality more than of those of H. filipjevi that recovered from exposure to such compounds.

These findings suggest that H. filipjevi is not a significant new threat to intensive cereal production in the UK and it is effectively controlled by fungi that have successfully controlled H. avenae for many years. The unexpected widespread distribution of H. filipjevi in the UK may have resulted from the current predominance of autumn-sown cereals but this would need further testing.

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