Preliminary studies revealed a distinct difference in size between the chromosomes of the two species of tomatoes, those of L. esculentum being 20-30 percent larger. Pairing and disjunction in the first meiotic division were regular except for occasional univalents in diakinesis. In a more detailed study the following facts were noted. The somatic chromosomes are small rods with median or sub-median constrictions, those of L. esculentum being distinctly larger. At pachytene of meiosis pairing occurs between all sets but there are certain places on certain chromosomes which never become paired but leave loops or free ends. Univalents are sometimes seen at diakinesis, presumably due to a reduction in the number of chiasmata. Although no univalents have been seen at metaphase there is occasional lagging such that one or more univalents do not become included in the interphase nucleus. This probably accounts for the observed 15-20 percent pollen sterility in the hybrid. The weakness of pairing would have the effect of materially reducing the chiasma frequency and thus restricting crossing over in a considerable part of the chromosome. This might be expected to have profound effects on genetic ratios should the genes under investigation lie in the affected parts.
Proceedings of the Iowa Academy of Science
©1935 Iowa Academy of Science, Inc.
Humphrey, L. M.
"Chromosome Behavior in the Species Cross Lycopersicum esculentum X L. pimpinellifolium,"
Proceedings of the Iowa Academy of Science, 42(1), 93-94.
Available at: https://scholarworks.uni.edu/pias/vol42/iss1/32