Notes on the cytogenetics of some South African Xiphinema species (Nematoda: Longidoridae)

Abstract

The cytogenetics of several South African species of Xiphinemawere studied and compared with the existing data for this genus from Europe. The process of oogenesis appears to be very similar in all species studied, with little interspecific and intraspecific differences. The ovaries of the South African specimens are larger, with more oogonia and oocytes. The chromosomes are also relatively larger, but could not be counted in oocytes during diakinesis, which usually represents the best stage. Chromosome numbers were therefore determined in the oogonia, which yielded quite accurate and consistent results. The diploid number of 10 seems to be constant in all species studied, but differs from one species of the X. americanum group, for which a number of five has been reportedy Polyploids were not encountered in any of the South African specimens.