Fresh tomato debris was inoculated with R. solanacearum
previously described (Zanón and Jordá, 2008) and was cut into
small pieces (2e4 cm) of stems and leaves. Infected plant material
was mixed with the growth medium in three doses [5 g, 10 g and
15 g, per 500 g of growing medium, a mixture of peat moss and
sand (3:1 v/v) which had been autoclaved (1 h at 121 C)]. Four pots
(15 cm diameter, 15 cm deep) per dose were filled with 500 g of
growth substrate. Negative controls were prepared with the same
doses using either residues of healthy tomato plants or only
substrate (dose 0). The assayed dosages were selected according to
Piedra Buena et al. (2006) and are equivalent to crop residue
amounts in greenhouse production systems.