DETECTION AND CYTOLOGICAL ANALYSIS OF TOMATO HAPLOIDS

Using the recessive character technique of detection, two haploid plants of Lycopersicon esculentum were selected among the progeny of a cross between non-irradiated individuals, homozygous recessive for three seedling markers, and wild type pollen previously exposed to thermal neutrons. The haploid plants were found to constitute a very suitable material for detailed cytological investigation. Evidence was obtained that the haploid chromosomes display in meiosis at least some degree of segmental homology during pachytene and first metaphase. This finding, which was confirmed by an analysis of distribution frequencies in anaphase, may shed new light on the speculations concerning basic chromosome number in the genus Lycopersicon. The presence of a nucleolus at each of the two poles in prophase II is reported, and interpreted as a proof that other chromosomes can assume in haploids the specific function of the nucleolar organizer when the latter is absent. © 1969 Martinus Nijhoff.