Resumo

GOMEZ, Sandra  e  ARBELAEZ, Germán. Effect of temperature on the latent period and sporangia production of Peronospora sparsa Berkeley in three rose varieties. Agron. colomb. [online]. 2005, vol.23, n.2, pp.239-245. ISSN 0120-9965.

Expensive handling, the low efficacy of downy mildew management strategies and the strong relationship with weather conditions place great importance on this disease in producing roses for export. This research was aimed at studying the pathogen's biology to understand its relationship with temperature and host variety in laboratory conditions. Sporangia of Peronospora sparsa from rose leaves with sporulation were collected in sterile water. A 30,000 sporangia per millilitre suspension was used for inoculating healthy detached leaves from 'Charlotte', 'Classy' and 'First Red' varieties grafted onto 'Manetti' and 'Natal Briar' rootstocks and others rooted directly. The research was carried out at 10, 14, 18 and 22 °C with regulating 12-hour periods of light and dark. The sporulation index (SI) and sporangia production per cm² leaflet were evaluated after seven days' inoculation. Classy presented the shortest latent period in this study whilst the longest was observed in 'First Red'. Temperatures higher than 18 °C were favourable for pathogen sporulation. The highest SI was observed in the 'Classy' variety, 'Charlotte' presented a medium value and 'First Red' showed the lowest SI at the different temperatures evaluated. Variations in latent period and sporulation intensity were specific according to variety and temperature.

Palavras-chave : downy mildew; pathogenicity cycle; rootstocks; Sabana de Bogotá.

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