Synapsis and chiasma formation in four meiotic mutants of tomato (Lycopersicon esculentum).

Synapsis and chiasma formation were studied in pollen mother cells of four meiotic mutants of tomato. The four mutants displayed defects in the assembly of the synaptonemal complex (SC) covering the whole range from almost complete absence of synapsis to complete synapsis at pachytene. In three mutants, we found a good correlation between the number of bivalents connected by at least one tripartite SC segment at pachytene and the number of chiasmatic bivalents at metaphase I. We suggest that in tomato functional chiasmata are only formed in the context of the tripartite SC.