Survival of Xanthomonas axonopodis pv. phaseoli var. fuscans in common bean leaflets on soil.

The aim of this study was to evaluate the survival of a strain of Xanthomonas axonopodis pv. phaseoli var. fuscans (Xap), resistant to streptomycin sulphate, in common bean leaflets placed on the soil surface and buried at a depth of 10 and 15 cm. Four assays were carried out from November 1998 to December 2000 in Bandeirantes (Parana, Brazil). The leaflets were collected every 15 days, crushed and the dilution-plated on a semi-selective medium. Under mild temperatures and low rainfall, Xap survived for 65 to 180 days in the leaflets on the soil surface, and for 30 to 120 days in those incorporated in the soil, regardless of the depth. When higher rainfall and temperatures occurred, the survival was from 45 to 60 days in the leaflets on the soil surface and from 30 to 45 days in those buried 10 or 15 cm deep.