Identification of a new Fusarium culmorum gene involved in foot and root rot on durum wheat by transposon tagging

FRANCESCA SPANU; IRENE CAMBONI; BARBARA SCHERM; VIRGILIO BALMAS; ISMAEL MALBRÁN; MATIAS PASQUALI; QUIRICO MIGHELI

Doha

Conferencia; Qatar Foundation Annual Research Conference; 2013

Qatar Foundation for Education, Science and Community Development

Fusarium culmorum is an ubiquitous soil-borne plant pathogenic fungus that produces type B trichothecene mycotoxins. On wheat and other small grain cereals, it induces both a direct damage following production loss and an indirect damage due to mycotoxins that contaminate grains. The genome of F. culmorum is being sequenced but for many genes the function is still unknown. Therefore, the characterisation and identification of pathogenicity-related genes is essential in the build-up of alternative control methods against this pathogen. We adopted a transposon tagging approach with the mimp1/impala double component system to select mutants of F. culmorum altered in their metabolic or morphological processes and impaired in their aggressiveness during the first step of interaction between this fungus with the host plant. In vitro bioassays were carried out to identify altered phenotypic characters in putative mutants growing on potato dextrose agar (PDA) amended with 2 M sorbitol, 1 M NaCl (osmotic stress), 30 mM potassium persulphate (oxidative stress) and 0.02% sodium dodecylsulphate (SDS). To test thermal stress resistance of putative mutants, radial colony growth was tested on PDA at 37°C and 8°C. An in vitro pathogenicity test was performed by placing durum wheat seeds on 10 mycelium plugs in a Petri dish and incubating 3 days in the dark at 25°C. To confirm the result obtained in vitro, in planta assays were performed in greenhouse conditions. Several F. culmorum mutants were obtained with altered phenotypic characters, including stunted vegetative growth and loss of pathogenicity towards wheat stem base/root tissue. Cloning of sequences flanking the mimp1 element obtained by splinkerette PCR in one of the selected mutants (R38) allowed us to identify an hypothetical gene with orthologs only in the fungal domain. The first mimp1-tagged gene involved in FRR pathogenicity adds to the few other genes known to play a role in this disease. Given that this gene contains a leucin zipper domain, it may likely have a regulatory role that will be further investigated by RNA seq.