Pathogenicity of the root-knot nematode Meloidogyne incognita on cacao. In: Theobroma v. 6 p. 55-65, 1976.

Abstract

Tbe pathogenicity of the root-knot nematode, Meloidogyne incognita to caca o (Theobroma cacao L.) varo "Catongo" bas been studied at three inoculum levels under grecnhouse conditions. Significant differences in plant growth appeared 17 weeks after lnoculation. The inoculated plants were stunted and unthrifty with iaUed root system. Comparing the inoculated plants wlth control at 37 weeks after inoculation lt was found that dry plant weigbt, stem diameter, and plant height had decreased 31 2~. to 47.9'7~ IO.6~. to 17.4~. and 20.6~. to 28.4~., respectively. Histopathological observations of inoculated plant revealed giant cell formalion and hyperplasia of the vascular parenchymatous cells. The stelar region was completely disorganized with partiaI to total destruction of xylem, phloem, pericycle and endodermis. Adults females were found embedded in the c ortex with giant c~lls around their heads and egg masses deposited on the root surface through ruptures in the cortex. The nematode is higbIy pathogenic to cacao and it is probable that it plays a primary role in the eliology of "sudden death" disease under field conditions.