A Comparison of Nematode and Bacteria-Colonized Galls Induced byAnguina agrostisinLolium rigidum

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Abstract
Morphological differences between seed galls containing nematodes and those colonized by bacteria are described. The 2 types of galls can be readily recognized; the former are dark brown and the latter are yellow. Sectioning and viewing under Nomarski optics showed that the walls of galls containing nematodes are about twice the thickness of the walls of those containing bacteria. Scanning electron microscopy showed the orderly manner in which both nematodes and bacteria are packed in the anhydrobiotic galls. Transmission electron microscopy of freeze-etch replicas and ultrathin sections of both types of galls revealed the presence of particles in the galls containing bacteria. These particles are 25-30 nm in diameter, occur in close association with the bacteria and their capsules, and are found in large numbers in the walls of the galls. The possible nature of these structures, and their relationship to toxin production in the galls that contain bacteria, are discussed.