The presence of stem nematodes (Ditylenchus spp.) is a principle reason for rejecting faba bean seed for further cultivation and processing for human consumption. In the UK, annual faba bean yield losses due to the stem nematodes are estimated at between £400k and £4m per annum. A further estimated £6.25m is lost to the industry over 5 years due to the withdrawal of infested land from faba bean cultivation. Since chemical nematicides are not available and crop rotation is impractical due to the polyphagy of stem nematodes, only plant resistance offers a cost-effective and environmentally benign means of control. The present study investigates the species status of stem nematodes on faba bean in the UK in order to evaluate the level of resistance in both commercial cultivars and previously identified resistant sources of faba bean. For the first time this study has shown that D. gigas n. sp. is the predominant stem nematode species in the UK faba bean. Development of various screening methodologies has led to the efficient selection for stem nematode resistance in faba bean germplasm. Increased susceptibility was observed in spring sown genotypes, as shown by high reproduction of stem nematode, greater stem swellings and lesions. It has been demonstrated that virulence of D. gigas n. sp. increased with repeated reproduction on the susceptible genotype. Conclusively environmental conditions are shown to influence stem nematodes incidence in faba bean seeds. Increased stem nematode infestation within seeds was more pronounced in cool and humid years. This work established the differences in gene structure of endo-β-1,4-glucanases in D. gigas n. sp. and D. dipsaci sensu stricto, which are known to be a cell-wall degrading genes. Complex host-pathogen interactions have been shown by increased relative expression of dg-eng gene in planta of susceptible and resistant genotype. In continuation from this project the selected faba bean genotypes are being used in developing new cultivars with resistance to D. gigas n. sp. Understanding of the stem nematode parasitism process in relation to the development of novel approaches for control of stem nematodes is discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:578032 |
| Date | January 2011 |
| Creators | Stawniak, Natalia |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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