Cytogenetic analysis of Lycopersicon esculentum (plus) Solanum etuberosum somatic hybrids and their androgenetic regenerants

The aim of the study was to characterize genomic relationships among cultiv ated tomato (Lycopersicon esculentum Mill.) (2n=2x=24) and diploid (2n=2x=2 4) non-tuberous wild Solanum species (S. etuberosum Lindl.). Using genomic in situ hybridization (GISH) of mitotic and meiotic chromosomes, we analyze d intergeneric somatic hybrids between tomato and S. etuberosum. Of the fiv e somatic hybrids, two plants were amphidiploids (2n=4x=48) mostly forming intragenomic bivalents in their microsporocytes, with a very low frequency of multivalents involving the chromosomes of tomato and S. etuberosum (less than 0.2 per meiocyte). Tomato chromosomes showed preferential elimination during subsequent meiotic divisions of the amphidiploids. Transmission of the parental chromosomes into microspores was also evaluated by GISH analys is of androgenic plants produced by direct embryogenesis from the amphidipl oid somatic hybrids. Of the four androgenic regenerants, three were diploid s (2n=2x=24 or 2n=2x+1=25) derived from reduced male gametes of the somatic hybrids, and one plant was a hypertetraploid (2n=4x+4=52). GISH revealed t hat each anther-derived plant had a unique chromosome composition. The pros pects for introgression of desirable traits from S. etuberosum into the gen e pool of cultivated tomato are discussed.