Influence of temperature on powdery mildew development in TGR-1551

P. Beraldo-Hoischen, A.I. López-Sesé
Several plants of 'TGR-1551', a Zimbabwean melon accession resistant to races 1, 2 and 5 of Podosphaera xanthii, and the susceptible Spanish cultivar 'Bola de Oro' were inoculated with powdery mildew race 2 at two different temperatures (18-22 and 25-30°C) in order to study the plant-pathogen interaction. Fungal development was evaluated at microscopic level through several parameters such as the number of penetrated points, detected by callose accumulation with the double aniline-blue-calcofluor staining technique, at 48, 72, 96 and 120 h post inoculation (hpi), as well as the number of conidiophores at 120 hpi stained with an ink/acetic acid solution. The melon accessions 'PMR 45' and 'WMR 29', susceptible and resistant to race 2 respectively, were used as control lines at 48 and 120 hpi. At low temperature, 'TGR-1551' showed a non-resistant phenotype since the number of penetration points increased with time, as it is also observed for susceptible lines. Likewise, a high number of conidiophores were detected, although in lower quantities than in the susceptible lines. At high temperature, however, most of fungal conidia deposited on 'TGR-1551' plants stopped its development at germ tube or primary hyphae stage, and no conidiophores were observed at 120 hpi. A similar behavior was recorded for 'WMR 29'. The susceptible melon lines, 'Bola de Oro' and 'PMR 45', showed a great fungal development at both temperatures, being the greatest values observed at high temperature. This environmental factor might be affecting significantly the resistance of several melon genotypes to powdery mildew.
Beraldo-Hoischen, P. and López-Sesé, A.I. (2017). Influence of temperature on powdery mildew development in TGR-1551. Acta Hortic. 1151, 211-216
DOI: 10.17660/ActaHortic.2017.1151.33
callose, conidia, Cucumis melo, Podosphaera xanthii, powdery mildew

Acta Horticulturae