ABSTRACT: Multiple pathogens affect sugarcane, among them Puccinia melanocephala, the causal agent of brown rust. This disease was first reported in Cuba in 1979 when it was responsible for a severe attack on the main sugarcane variety B4362. The aims of the present study were to give an overview of sugarcane brown rust in Cuba and show the current disease situation in the country. A retrospective analysis regard to sugarcane cultivar composition resistant to brown rust in Cuba was carried out. In addition 154 genotypes, including the most used progenitors in the breeding program and commercial varieties were evaluated under natural infection conditions. The identity of P. melanocephala was verified by Polymerase Chain Reaction (PCR) and by sequencing the ITS1 region. After the introduction of P. melanocephala into Cuba, the susceptible variety, B4362, was replaced by Ja60-5 which remained resistant until 1998. Since 2002, a varietal policy supported by a governmental resolution establishing that any single cultivar cannot occupy more than 20 % of the production area for each production company, local area and province, has been applied. Out of the genotypes evaluated, 49 showed resistance to the disease and 35 intermediate behavior, while 39 were susceptible and 31, highly susceptible. P. melanocephala was detected by PCR in all symptomatic samples and its identify confirmed by sequencing the ITS1 region. The adopted measurement together with permanent phytosanitary monitoring and commercial release of resistant or intermediate cultivars succeeded in avoiding any new epidemic. Inoculum pressure was reduced, even on susceptible and highly susceptible varieties since, by resolution, they cannot occupy more than 10 % of the planted area.

Molecular exclusion chromatography can be used to purify filamentous phages which are the most commonly used virus in phage display technology of peptides and proteins. Bacteriophages were precipitated from culture supernatant using polyethylene glycol and they were loaded in a 100 cm high CL-4B Sepharose matrix using phosphate buffer as mobile phase. We recovered 61.3% of total phage loaded. SDS-PAGE analysis showed a high purity of these preparations. Molecular exclusion chromatography is an attractive alternative method for purifying filamentous phages.

La cromatografía de exclusión molecular puede ser usada para purificar fagos filamentosos, el virus bacteriano más usado en la tecnología de presentación de péptidos y proteínas en la superficie de los fagos. El bacteriófago, luego de ser precipitado del sobrenadante de cultivo con polietilenglicol, fue aplicado a una columna de Sepharose CL-4B de 100 cm de altura, usando como fase móvil solución tampón fosfato (PBS). Se obtuvo un 61,3% de recobrado del fago total aplicado y, mediante el análisis por SDS-PAGE, se verificó la pureza de estas preparaciones. La cromatografía de exclusión molecular es una metodología atractiva para la obtención de preparaciones de bacteriófagos con alta pureza.