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Summa Phytopathologica

Print version ISSN 0100-5405

Abstract

GARCIA, Ely Oliveira; CASAGRANDE, Marcos Virgílio; RAGO, Alejandro Mário  and  MASSOLA JUNIOR, Nelson Sidnei. Preservation of uredospores of Puccinia melanocephala, the causal agent of sugarcane rust. Summa phytopathol. [online]. 2007, vol.33, n.2, pp. 152-156. ISSN 0100-5405.  http://dx.doi.org/10.1590/S0100-54052007000200009.

The seasonality in the appearance of sugarcane rust makes it difficult to obtain in any season of year, adequate quantities uredospores for artificial inoculations in a breeding program. This research aimed to develop a long-term storage methodology to preserve uredospores of Puccicinia melanocephala to keep their viability and infectivity. Uredospores were collect using a vacuum pump from naturally rusted leaves. Part of these uredospores was dehydrated in silica gel or lyophilized and the other part was not dehydrated. Then they were all stored at different temperatures (room temperature, 5ºC, -20ºC and -80ºC). Subsequently, uredospores viability was periodically evaluated using the water-agar method. After the fourth month, the infectivity was also evaluated through inoculations in leaves of the sugarcane susceptible variety SP70-1143 following disease evaluation. Regardless of the dehydration treatment used, uredospores stored at room temperature and at 5ºC were viable for the maximum periods of 1 and 2 months, respectively. The best results were obtained with the silica gel dehydration treatment followed by storage at -20ºC or -80ºC. Even after one year of storage, these uredospores were able to cause rust in inoculated plants at levels of severity which are adequate to start screening tests for sugarcane resistance to rust.

Keywords : viability; infectivity; spores; uredinales.

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