The role of phytohormones in basal resistance and Trichoderma-induced systemic resistance to Botrytis cinerea in Arabidopsis thaliana

Abstract

Thirty-six phytohormone-affected mutants of Arabidopsis thaliana (L.) Heynh. and their parental ecotypes were tested for resistance/susceptibility to Botrytis cinerea Pers.; Fr. and ability to develop Trichoderma-mediated induced systemic resistance (ISR). Ecotype Colombia-0 (Col-0) was relatively resistant to B. cinerea, and Trichoderma harzianum Rifai T39 application at sites spatially separated (roots) from the B. cinerea inoculation (leaves) resulted in reduction of grey mold symptoms. Ecotypes Wassilewskija-4, Nossen-0 and Landsberg-0 had low levels of basal resistance to B. cinerea and were unable to express ISR. Mutants derived from ISR-non-inducible ecotypes displayed ISR-non-inducible phenotypes, whereas the ISR inducibility of mutants derived from the ISR-inducible genotype Col-0 varied according to the type of mutant. Thus, salicylic acid (SA)-impaired mutants derived from Col-0 were ISR-inducible, while ethylene/jasmonic acid (ethylene/JA)-impaired mutants of the same origin were ISR-noninducible. SA-impaired mutants retained basal level of resistance to B. cinerea, while most ethylene/JA-impaired mutants were highly susceptible. Abscisic acid-and gibberellinimpaired mutants were highly susceptible to B. cinerea and showed ISR-non-inducible phenotypes irrespective of their lines of origin. Auxin-resistant mutants derived from Col-0 were ISR-inducible; mutant originating from Landsberg-0 and mutants which were resistant to both auxin and ethylene were ISR-non-inducible. Most of the arabidopsis genotypes which were unable to express Trichoderma-mediated ISR against B. cinerea exhibited enhanced susceptibility to this pathogen. T. harzianum treatments enhanced the growth of arabidopsis plants regardless of genotype or ISR inducibility.

Identifying Beneficial Qualities of Trichoderma parareesei for Plants

“…In accordance with previous studies in which root application of T. harzianum or T. atroviride was able to reduce the leaf lesion area caused by B. cinerea (49,54,55), T. parareesei T6 also triggered ISR against this foliar pathogen.…”

Plant-beneficial effects of Trichoderma and of its genes

“…The ISR triggered by Trichoderma occurs through the JA/ET signalling pathway similarly to PGPR-ISR (Shoresh et al, 2005), as confirmed by several authors: (i) cerato-platanin Sm1 is required for T. virens-mediated ISR against Colletotrichum graminicola in maize (Djonovic et al, 2007), (ii) Trichoderma treatment of JA/ET-deficient Arabidopsis genotypes leads to enhanced susceptibility to Botrytis cinerea (Korolev et al, 2008), (iii) ISR triggered by PGPR and Trichoderma converges upstream from MYB72, an early key component of the onset of ISR (Segarra et al, 2009). However, other studies have shown that in the T. asperellum-cucumber interaction the induction of plant responses is a time-and concentration-dependent phenomenon, and in the first hours of contact a SARlike response is observed, with an increase in SA and peroxidase activity.…”

Jasmonate signaling in plant interactions with resistance-inducing beneficial microbes

“…Likewise, ISR triggered by the PGPF Penicillium sp. GP16-2, Trichoderma harzianum T39 and P. indica was shown to be blocked in JAand ET-signaling mutants of Arabidopsis (Hossain et al, 2008;Korolev et al, 2008;Stein et al, 2008).…”