Can the leaf age influence the susceptibility to bacterial-leaf-spot and bacterial-halo-blight on coffee seedlings?

ABSTRACT: Pseudomonas syringae van Hall, 1902, causes yield losses in innumerous economic important crops. On coffee trees, P. syringae pv. garcae causes the bacterial-halo-blight (BHB) and P. syringae pv. tabaci the bacterial-leaf-spot (BLS). Recently, these diseases incidence has increase in occurrence areas and aggressiveness in Brazil. Although leaf age plays a role in the severity response of BHB, it is not known yet if this phenomenon also occurs in coffee-BLS interaction, and with highly virulent strains. So, we examined differences in the diseases severity by inoculation of P. syringae pv. garcae and P. syringae pv. tabaci strains on coffee leaves with different ages, to compare this aspect with coffee-BLS interaction. Our results showed that, for both pathovars, the severity was greater at the first internodes leaves, although for the most aggressive strains it was quite similar on any leaf age.

摘要：丁香假单胞菌（Pseudomonas syringae van Hall, 1902）可在众多经济重要作物上引发产量损失。在咖啡树上，丁香假单胞菌咖啡致病变种（P. syringae pv. garcae）可导致细菌性晕枯病（BHB），丁香假单胞菌烟草致病变种（P. syringae pv. tabaci）则引发细菌性叶斑病（BLS）。近年来，这两种病害在巴西的发生范围与致病力均呈上升态势。尽管叶龄会影响细菌性晕枯病的病情严重程度，但目前尚不明确该效应是否同样存在于咖啡与细菌性叶斑病的互作体系中，且针对强致病力菌株的相关研究仍属空白。为此，本研究通过对不同叶龄的咖啡叶片接种丁香假单胞菌咖啡致病变种与烟草致病变种菌株，探究病害严重度的差异，并将该结果与咖啡-细菌性叶斑病互作体系的相关特征进行对比分析。研究结果显示，对于两种致病变种而言，第一节间的叶片病情严重度更高；但对于致病力最强的菌株而言，不同叶龄叶片的发病严重度并无显著差异。