Caracterização de solos de pernambuco quanto à supressividade a Pectobacterium carotovorum subsp. carotovorum

Abstract

The soft-rot caused by P. carotovorum subsp. carotovorum (Pcc) is a limiting factor for vegetable harvests in Pernambuco State. Soil characteristics and environmental factors may influence Pcc population and development of soft-rot. This work aimed to evaluate the extinction rate of Pcc population in 24 soil samples of Pernambuco and analyze physical, chemical and microbiological soil characteristics associated with suppressiveness or conduciveness for the pathogen. In the study of soil influence on Pcc population a rifampicin-resistant mutant was utilized (Pcc127Rif). The extinction rate of population (TERP) was calculated and ranged from 0.0547 to 0.6327 log (CFU)/d. Six soils showed suppressiveness for Pcc127Rif while five presented conduciveness. The soil groups based on the TERP of Pcc127Rif did not correlate with municipalities, types of vegetation cover at the sampling time or soil textural classes. Considering all soils, there were no significant correlations (P<0.05) among TERP of Pcc127Rif and chemical, physical and microbiological characteristics of soils. Considering the six most suppressive soils, the TERP of Pcc127Rif significantly correlated with apparent soil density (r = 0.76), total bacterium population (r = 0.82) and Bacillus sp. (r = 0.80). The Bacillus sp. population correlated with apparent density, but not with total bacterium population. Considering the five most conducive soils there was correlation between TERP of Pcc127Rif and Bacillus sp. population (r = -0.86).