Reaction of Tobacco and Rice Leaf Tissue Infiltrated with Burkholderia glumae or B. gladioli

Reaction of tobacco and rice leaf tissue infiltrated with either strains of Burkholderia glumae or B. gladioli was investigated. Visual alteration areas of tobacco leaf at sites infiltrated with high concentration (more than 10⁷ cells/ml) of the bacteria were categorized into two types, one causing necrosis with hypersensitive-like reaction (HLR) within 24 hr of infiltration, and the other developing only yellowish discoloration. Living bacterial cells and the toxoflavin were effective for necrosis induction, whereas heat-killed cells, bacterial lipopolysaccharide (LPS) and extracellular polysaccharide (EPS) were ineffective. In the case of B. glumae, necrosis occurred with toxoflavin producing strains. No necrotic lesions developed with toxoflavin non-producing strains. All strains of B. gladioli induced necrosis with water soaking lesions in tobacco leaf. Infiltration of toxoflavin producing strains of B. glumae and B. gladioli to rice leaf caused necrosis or a chlorotic spot on the leaf. A toxoflavin dose of more than 100μg/ml induced necrosis, suggesting close relationship between virulence to rice and necrosis inductivity to an uncongenial plant such as tobacco. Thus, the principle which induces HLR can be regarded as an essential attribute for pathogenicity. In contrast to the reaction of rice leaf toward toxoflavin, necrosis in tobacco leaf could not simply be a reaction to toxoflavin but rather to additional unknown factors.