Induced resistance activated by a culture filtrate derived from an avirulent pathogen as a mechanism of biological control of anthracnose in strawberry

CHALFOUN, N.R.; CASTAGNARO, A.P.; DIAZ RICCI, J.C.

BIOLOGICAL CONTROL

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2011

1049-9644

In a previous report, it was described that strawberry plants pre-treated with an avirulent isolate of Colletotrichumfragariae (M23) acquired resistance to a virulent isolate of Colletotrichum acutatum (M11)causing anthracnose. In this report we present evidence that the eliciting activity can be found not onlyin conidial extracts but in culture supernatants of the avirulent pathogen as well. Plants of the cv. Pájarotreated with the culture filtrate (CF) derived from M23, 3 days prior to the inoculation with M11 showedsignificantly reduced disease severity as compared to control plants and the disease was completely suppressedwhen plants were pre-treated 7 days before the challenge inoculation with M11. The same effectwas achieved when a single leaf was sprayed with CF, suggesting that the resistance acquired is systemic.Control treatments showed that none of the active extracts inhibited the growth of the virulent pathogen,indicating that the protection effect was due to the induction of a defense response. The latter was confirmedby the accumulation of reactive oxygen species (e.g. hydrogen peroxide, superoxide anion) andthe deposition of lignin and callose, usually associated to plant defense, after the CF treatment. Experimentscarried out with other strawberry cultivars treated with CF showed that also protected themagainst different virulent isolates, suggesting that the response observed is cultivar-nonspecific. Theseoutcomes indicate that the protection against anthracnose in strawberry involves a phenomenon ofinduced resistance (IR) by action of defense-eliciting molecules produced by M23.