Pachytene karyotype analysis of the nematode Meloidogyne spartinae in relation to the genus Meloidogyne.

Seven synaptonemal complexes (SC) were present in the pachytene nuclei of Meloidogyne spartinae. The SC was bipartite and consisted of two lateral elements, while lacking a striated central element. This pattern was similar in all Meloidogyne species studied thus far with the exception of M. microtyla. Each SC was attached by only one end to the nuclear envelope while the other end remained unattached and was free in the nucleoplasm. A bouquet formation at pachytene was absent. An average of eight recombination nodules were present on the SC during all stages of pachytene, although the length of SC increased approximately 77%, from an average of 78 to 138 microm from early to mid-late pachytene. In M. spartinae, there was no apparent relationship between SC length and amount of recombination at pachytene. In addition, nuclear volume increased >60% during pachytene while nucleolar volume decreased by approximately 35%. Two nucleolar organizer regions (NOR) were present during mid-pachytene, whereas other stages had only one NOR. This is the first time that two nucleoli have been identified at pachytene in any nematode. They were both the same chromosome yet in reverse order relative to the telomere attached to the nuclear envelope, suggesting that each telomere was competent to interact with the nuclear envelope.