Historically, coffee plants showing atrophy and scorch branch were attributed to nutritional disorders due to successive high yields. The bacteria XylelLa fastidiosa Wells et al. is currently the most reported pathogen related with the problem and the symptoms are associated with stress. Although the bacteria has been well studied in the United States particularly in grape, few is known about the pathogen-host-vector relationship. The present studies were carried out with coffee plants (grafted or not grafted) aiming to evaluate xylem vessels obstruction in various plant parts, including branches with and without external symptom expression. Two seasons of plantation were assessed in a year and the parameters evaluated were: nutritional and structural bacteria as affected by water supply to the bacteria. The experiments were installed in 1986 in the coffee region of Garça, São Paulo State. The samples, for anatomic studies, were taken in two period of the year 2000: April - May (water stress) e November - December (rainy periods). Leaf and soil samples for analyses were taken in April 2000. The highest proportion of xylem vessels obstruction due to the bacteria was noticed during the water stress period as compared with the rainy season. There were not significant differences on bacterium coffee effect between the two sampling periods. The bacterium presence did not show difference among nutritional leaf composition, however the symptomatic branches of some genetic material showed smaller concentration of some nutrients when compared with assymptomatic branches.
Coffee plants; conduction; nutrients; obliteration; seasonality; xylem
