Anatomy of Sunflower Stem Galls Induced by the Root-knot Nematode, Meloidogyne javanica

Anatamy of stem galls of sunflower (Helianthus annuus) infected by Meloidogyne javanica in a glasshouse experiment was studied. A progressive number of infective juveniles penetrated roots and stems of seedlings during germination in infetsed soilwith more than 8 eggs and juveniles/cm3 soil. Nematode infective stages penetrated stem tissues and established thei feeding sites mainly in the cambium; stem swellings were caused by pronounced hyperthrophy of cambial cells at the feeding sites. The size of galls and the production of giant cells in the aerial part, induced by a single nematode, were similar to those observed on the roots. Egg masses with hardned gelatinous Matrix appeared within 50 days, usually protruding from the stem surface.