CYTOLOGY OF PARTHENOGENESIS OF 5 MELOIDOGYNE SPECIES

Oogenesis was investigated using a fluorescent staining technique with Hoechst 33258 in several isolates of facultative meiotic parthenogene tic -Meloidogyne hapla race A, M. chitwoodi, M. fallax - and obligate ameiotic (mitotic) parthenogenetic - M. hapla race B, M. javanica - an d isolate Xa of an unidentified species. Without fertilisation, the so matic chromosome number was restored by fusion of pronucleus and secon d polar body in M. hapla race A, M. chitwoodi, and M. Sallax isolates. In oocytes of isolate Xa, a second meiotic division occurred in a few cases while in all other cases the somatic chromosome number was rest ored by duplication of the chromosomes of the egg nucleus after the fi rst division. In one mono-female line of Xa, embryonic development occ urred within the body of the female and was genetically controlled. In M. hapla race B and M. javanica, maturation of the oocytes consisted of one mitotic division. This study confirmed that a large variation o f the mode of reproduction exists in Meloidogyne spp., which may be a reason for their world-wide success. In one M. hapla race A isolate, o nly 12 % of the oocytes of inseminated females contained sperm, and pr ophase I instead of prometaphase I oocytes were found posterior to the spermatheca. (C) Orstom/Elsevier, Paris.