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Narcissus Neck Rot: biology, epidemiology and control. - HH1748TBU

The main objective of this strategic research project is to gain information on the incidence and relative importance of three fungal pathogens of narcissus that have been shown to be present in bulbs displaying neck rot symptoms. This project aims to survey narcissus stocks representing most major and some minor cultivars grown throughout the industry and to determine the frequency with which Fusarium oxysporum f.sp. narcissi (FON), Penicillium hirsutum (PH) and Botrytis narcissicola (BN) are found in neck tissues of healthy and neck rotted bulbs. Novel molecular diagnostic techniques will be developed and tested to provide sensitive detection and accurate identification of these pathogens in planta. Variation within pathogen populations will be determined using both molecular and important biological characters such as virulence and fungicide sensitivity.

The proposed work conforms to MAFF's policy objective of identifying ways of reducing crop losses, improving product quality and optimising pesticide use in order to enable UK bulb growers to improve productivity and competitiveness. This project proposal also has the support of major sections of the UK bulb industry (see Appendix C - letters of support).

Results obtained here will provide greater knowledge about the role of each of the putative neck rot pathogens in commercial disease outbreaks and also about the variation within UK pathogen populations. The intention is to use this information to improve existing control strategies or develop novel ones, tailored to particular pathogens or pathogen combinations responsible for neck rot.
The overall objective of this project is to detect, identify and characterise the pathogens) that cause neck rot. The incidence of putative pathogens in neck rots of commercial narcissus stocks and variation within these natural populations s~~ill be determined.

1. To develop molecular methods to identify Fusarium, Penicillium and BotrVlis species.

Devise and test PCR-based diagnostic techniques for all three fungal genera (year l).

2. To determine the incidence of Fusoriunr, Penicillium and Botrytis species in commercial bulb stocks.

Apply diagnostic tests for the three fungal genera to rotted and healthy bulbs from commercial stocks of three cultivars from ten sources (years 1 and 4), and to single stocks from 20 sources (year 3).

3. To examine the variability within populations of FON, PH and BN.

Develop and apply molecular methods to detect variation within a collection of 20 FON isolates from neck and basal rots. Determine the specificity and virulence of these isolates in both bulb rot locations. Seek correlations between molecular and biological characters (year 2).

Examine variation within a wider range of F. oxysporum isolates, including low-pathogenicity and non-pathogenic isolates from bulbs and examples of other formae speciales (year 2).

Develop and apply similar molecular techniques to detect variation within collections of PH and BN isolates (20 of each, if available) obtained from commercial bulbs displaying neck rots. (year 3)

Determine variation in sensitivity to the fungicide thiabendazole within populations of the three pathogens obtained from neck rots (years 2. 3 and 4).
Determine the variation in virulence exhibited by populations of the three pathogens isolated from neck rots (years 2, 3 and 4).

4. To develop PCR-based diagnostics for neck rot pathogens

Test other primer sequences, derived from the DNA sequences used in objective 1 to provide genus-specific primers, that may show specificity at the sub-genus. species or (less likely) at forma specialis level.

Utilise sub-genus-, species- or forma specialis-specific RAPD or AFLP bands (identified in objective 3) to generate PCR primers with appropriate specificity unable to be achieved using the sequences in objective 1.
Project Documents
• Final Report : final report   (340k)
Time-Scale and Cost
From: 1999

To: 2003

Cost: £168,224
Contractor / Funded Organisations
Horticulture Research International
Disease Control              
Fields of Study