1. Laboratory of Molecular Evolution; Department of Genetics; Universidade Federal do Rio Grande do Sul; PoBox 15053, 91501-970 Porto Alegre RS Brazil
2. Institute of Plant Sciences; Altenbergrain 21 CH-3013 Bern Switzerland
3. Instituto de Botánica del Nordeste (UNNE-CONICET); Sargento Cabral 2131 Corrientes 3400 Argentina
4. Facultad de Agronomía; Universidad de la República; Av. E. Garzón 780 Montevideo 12900 Uruguay
5. Laboratory of Genomic and Molecular Biology; Pontifícia Universidade Católica do Rio Grande do Sul; Ipiranga 6681 Porto Alegre RS 90610-001 Brazil