Hybridizations Between formae speciales of Venturia inaequalis Pave the Way for a New Biocontrol Strategy to Manage Fungal Plant Pathogens

Abstract

Hybridization and adaptation to new hosts are important mechanisms of fungal disease emergence. Evaluating the risk of emergence of hybrids with enhanced virulence is then key to develop sustainable crop disease management. We evaluated this risk in Venturia inaequalis, the fungus responsible for the common and serious scab disease on Rosaceae hosts, including apple, pyracantha and loquat. Field isolates from these three hosts and progenies obtained from five crosses between formae speciales isolates collected from pyracantha (f.sp. pyracantha) and apple (f.sp. pomi) were tested for their pathogenicity on the three hosts. We confirmed a strict host specificity between isolates from apple and pyracantha, and showed that most isolates were able to cause disease on loquat. None of the 251 progeny obtained from five crosses between V. inaequalis f.sp. pyracantha and V. inaequalis f. sp. pomi could infect apple. If confirmed on more crosses, the inability of the hybrids to infect apple could lead to a novel biocontrol strategy based on a sexual hijacking of V. inaequalis f.sp. pomi by a massive introduction of V. inaequalis f.sp. pyracantha in apple orchards. This strategy, analogous to the sterile insect approach, could lead to the collapse of the population size of V. inaequalis and dramatically reduce the use of chemicals in orchards.

Meiotic recombination in Leptosphaeria maculans favours the rise of transgressive isolates adapted to a nonhost species, Brassica carinata

“…Although V77.1.11 produces more biomass than HB10.19 on B. carinata during infection, this biomass does not reach the biomass of L. maculans adapted to B. napus. Transgression segregation has been well described in plants (Rieseberg et al, 1999(Rieseberg et al, , 2003Stelkens and Seehausen, 2009), nevertheless, to date, only a few transgressive phenotypes were formally laid out in filamentous fungi (Cumagun et al, 2004;Voss et al, 2010;Gibson et al, 2014;Caffier et al, 2022). The transgressive isolates obtained in the progeny indicate that after only one sexual reproduction event, it is possible to generate strains of L. maculans adapted to B. carinata cotyledons.…”