The wild nightshade Solanum lycopersicoides possesses potentially valuable traits for tomato (Lycopersicon esculentum) improvement. Male sterility of the intergenic F 1 hybrid and its stylar rejection of tomato pollen have until recently prevented introgression. In the work herein described, ovule fertility was detected in the F 1 hybrid following pollinations with S. lycopersicoides. Pollinations of the F 1 with L. pennellii derived bridging hybrids resulted in a BC 1 population of 65 plants. BC 2 seed was obtained from most BC 1 individuals. Male fertility of the BC 1 plants ranged from 0 to 66% acetocarmine-stainable pollen. Of the 43 plants scored, 41 were diploids (2n = 24) and 2 were aneuploids (2n = 25 and 2n = 26). Chromosome pairing of the BC 1 at diakinesis and metaphase I averaged 11.1 bivalents per pollen mother cell. BC 1 and BC 2 plants were scored for 19 isozyme and morphological markers covering 10 of the 12 S. lycopersicoides chromosomes. Significant deviations from Mendelian segregation were observed for seven loci, with an excess of homozygotes (+/+) in all cases. Wa, which controls the white anther trait of S. lycopersicoides, was mapped to within 15 centiMorgans (cM) of Got-4, while Mdh-4 was closely linked to Pgi-1 (<2 cM). Plants heterozygous for the S. lycopersicoides allele (+/s) at Dia-2, Skdh-1, Wa, and Aco-1 showed significantly lower pollen stainability than homozygotes (+/+). Skdh-1 and Got-3 heterozygotes had less chromosome pairing at meiosis than homozygotes. These hybrids will permit the introgression of novel traits from S. lycopersicoides into tomato.
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Chetelat et al. (1989) studied this question.