Involvement of ethylene in wheat resistance to infection by Pyricularia oryzae

• Published in: Physiological and molecular plant pathology 2020-12, Vol.112, p.101526, Article 101526
• Main Authors: Rodrigues, F.C.T., Aucique-Pérez, C.E., Fontes, B.A., Ribeiro, D.M., Rodrigues, F.A.
• Format: Article
• Language: English
• Subjects: Ethylene; Foliar disease; Host defense responses; Plant hormones; Triticum aestivum
• ISSN: 0885-5765; 1096-1178
• DOI: 10.1016/j.pmpp.2020.101526

Considering wheat as an important staple food crop worldwide and the great impact of blast, caused by Pyricularia oryzae, to decrease yield, this study aimed to investigate the involvement of ethylene on wheat susceptibility to blast based on its basal and induced levels in plant tissues. Plants from cultivars BRS Guamirim and BRS 220 (susceptible and partially resistant to blast, respectively) were non-sprayed or sprayed with Ethrel (0.0001 M) 24 h before inoculation with P. oryzae. Blast severity was higher on ethylene-sprayed plants regardless of the cultivar. High foliar ethylene concentration for inoculated plants from cultivars BRS Guamirim and BRS 220 was associated with an increase in leaf tissues susceptibility to blast. Ethylene was synthesized on inoculated leaves regardless of ethylene spray. Expressions of the genes 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) 1, ACS 2, and ACC oxidase (ACO) were lower for plants from cultivar BRS 220 which showed lower blast severity. Peaks on the expressions of ACS 1 and ACS 2 genes for plants from cultivar BRS Guamirim non-sprayed with ethylene were stimulated by P. oryzae infection. PR-1 gene expression enhanced in response to ethylene spray indicating an increase in wheat resistance to blast mainly for plants from cultivar BR 220. In general, peroxidases, phenylalanine ammonia lyases and poliphenoloxidases activities were kept stable from 48 to 96 h after inoculation (hai) but seemed to be affected by both ethylene spray and fungal infection. For inoculated and ethylene-sprayed plants from cultivar BRS 220, a peak for chitinase activity occurred at 96 hai while β-1,3-glucanases activity was kept higher for inoculated plants from 48 to 96 hai. β-1,3-glucanases activity enhanced upon P. oryzae infection but was not potentiated by ethylene. The concentration of photosynthetic pigments decreased for inoculated plants from cultivar BRS Guamirim due to high blast severity. In conclusion, ethylene biosynthesis on wheat leaves was triggered by P. oryzae infection and host defense responses were activated. •Blast severity was higher on ethylene-sprayed plants regardless of the cultivar due to high foliar ethylene concentration.•Ethylene was synthesized on inoculated leaves regardless of ethylene spray.•The genes involved in ethylene biosynthesis were lower expressed for plants of the partially resistant cultivar.•Peroxidases, phenylalanine ammonia lyases, and polyphenoloxidases activities were affected b