Desynapsis due to temperature stress in three species of Solanum L

Microsporogenesis was normal during summer in S. melongena and S. violaceum and during monsoon in S. torvum. The same plants showed desynapsis during other seasons of flowering; winter in the first 2 species and summer in the last one. Normal meiosis was characterized by the chromosomes pairing into 12 bivalents, regular segregation and high pollen fertility (86.5%-94.6%). Average per cell chromosome association at metaphase I during desynaptic meiosis was 5.72II+12.56I in S. torvum, 7.63II+8.73I in S. melongena and 9.26II+5.47I in S. violaceum. Microspore mother cells in a few flower buds of S. violaceum showed complete lack of pairing which may represent a case of asynapsis. Anaphase I showed irregular segregation, univalent laggards and precociously separating chromatids. In S. torvum, flower development stopped after microsporogenesis so that no pollen grains were formed. Pollen stainability in the other 2 species was low (2.6% in S. violaceum and 14.7% in S. melongena). Both per cell and per bivalent chiasma frequency were reduced during desynaptic meiosis. Desynapsis and the other observed abnormalities are ascribed to temperature stress.