The reaction of two commercial varieties of Capsicum annuum (´Rubia-R´ and ´Silver´), and two experimental ones (AF 6203 and AF 6185) to an Argentinian population of Nacobbus aberrans from Catamarca province was evaluated. All varieties, except the former, carried resistance genes to Meloidogyne spp. (N, Me 3, and an unknown gene). Tomato plants were used as controls. Segments of non-infected roots and roots with galls induced by the nematode were fixed in FAA, dehydrated in a graded series of alcohol, and embedded in histowax. Nine-eleven um thick sections were triple-stained and mounted with DPX. Syncytia developed in all cases; they were detected in cortex and central cylinder in tomato, and mainly in central cylinder in pepper. The cells, of variable shapes and sizes, were delimited by thickened, frequently interrupted walls. The dense and granulose cytoplasm exhibited hypertrophic nuclei with higtly evident nucleoli. In general, a considerable reduction of vascular tissues was noticed. While the syncytium occupied a large part of the central cylinder in all cases, in the AF 6203 variety the syncytium did not reach the cortex in its radial expansion. The preliminary results obtained show a possible differential susceptibility depending on the varieties. The genes that confer resistance to Meloidogyne spp. in the pepper varieties tested did not prevent these plants from the attack of the N. aberrans population studied.
