EFS12- Book of abstracts - Contact

SESSION 3: PATHOGENESIS – EPIDEMIOLOGY AND POPULATION
GENETICS
P44 - A rapid in vitro assay to select mutants of
Fusarium impaired in pathogenicity.
F. Spanu 1 , B. Scherm 1 , V. Balmas 1 , I. Camboni 1 , A. Marcello 1 , M. Pasquali 2 ,
Q. Migheli 1
1 Dipartimento di Agraria - Plant Pathology and Entomology Unit and Unità di ricerca Istituto Nazionale
di Biostrutture e Biosistemi, Università degli Studi di Sassari, Via E. De Nicola 9, I-07100 Sassari, Italy.
2 CRP - Gabriel Lippmann, Environment and Agro-Biotechology Department, 41, rue du Brill, L-4422
Belvaux, Luxembourg
E-mail: fspanu@uniss.it
Fusarium culmorum, along with Fusarium graminearum and Fusarium
pseudograminearum, is one of the most important pathogens of wheat worldwide,
causing foot and root rot (FRR) and fusarium head blight (FHB). In the central and
southern areas of Italy, F. culmorum is predominant as the FRR causal agent on
durum wheat. Symptoms include pre- and post-emergence death of the
seedlings, brown discoloration on coleoptiles, roots and pseudostem, brown
lesions on the basal portion of the stem, tiller abortion and formation of
whiteheads, resulting from premature death of the plant. As a consequence,
significant yield losses are reported. Knowledge on genes triggering FRR on
durum wheat seedlings is still limited. F. culmorum mutants originating by random
and targeted insertional mutagenesis methods are being analysed in their
developmental capability, level of virulence and aggressiveness during the first
steps of kernel colonisation. However, greenhouse experiments are difficult to
perform for large collections of putative mutant strains due to the need of large
facilities, temperature and humidity control, and the time required (three to four
weeks after inoculation) to observe the first symptoms. We have developed a
simple in vitro pre-selection bioassay to analyse the development of fungal
hyphae during the first steps of colonisation, consisting in placing - for each strain
to analyse - 10 mycelium discs (Ø 90 mm) bearing one durum wheat seed into a
Petri dish and incubating 3 days in the dark. While the wild-type strain entirely
surrounded the seed by forming a complex network of thick and sturdy hyphae,
thus preventing germination before coleoptile growth, mutant strains impaired in
pathogenicity did not hinder the emergence of the primary root from the caryopsis.
This method proved to be as reliable as in planta assays, suggesting a potential
role for general use of in vitro testing of FRR-impaired mutants. We propose to
further validate this test on a broader collection of strains altered in their virulence
within the frame of an inter-laboratory collaboration.
Keywords: Foot and root rot, durum wheat, seed germination, bioassay, fungal
virulence
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