The worldwide area dedicated to peach cultivation is expanding. In 2010, the crop covered an area of 1,537,400 ha with an average yield of 13,190 kg·ha−1 (FAOSTAT–Statistical Database of the Food and Agriculture Organization of the United Nations, 2012). In Brazil, the production of 220,739 tons of fruit is still not sufficient to meet domestic market demand, and ≈21,500 tons of fresh fruit (peaches and nectarines) and 9,000 tons of processed fruit were imported in 2010. Exportation of fresh fruits was practically nil and only 930 tons of canned fruits were exported (IBRAF–Instituto Brasileiro de Frutas, 2012).
The expansion of peach culture to humid subtropical regions has been possible as a result of selection and release of low-chill cultivars. BLS caused by Xanthomonas arboricola pv. pruni (Smith, 1903) Vauterin et al., 1995, is an increasing problem for peach growers in warmer subtropical regions, and preventive techniques should be emphasized because chemical control is generally ineffective.
According to Battilani et al. (1999), primary infections of BLS are always established after at least three consecutive rainy days with temperatures between 14 and 19 °C. Disease progression is correlated with the number of rainy days during a growing season, and precipitation accounts for more than 90% of the variability in the incidence and severity of infection represented in a logistic regression model.
The reliable detection of peach germplasm resistant to BLS with potential use in subtropical climates is strategically important. Resistant genotypes would reduce production costs, enabling increased cultivation in subtropical areas. Resistance to BLS is considered to be a horizontal-type resistance and moderately heritable, and it should be possible to incorporate it into new peach selections (Topp et al., 1993).
The aim of the present research was to classify peach genotypes based on their susceptibility to BLS and to examine the correlation between bacterial reaction and morphological features of leaves, phenology, productivity, and climate.
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