Genetic studies of Solanum sitiens and hybridization with tomato.

摘要

This study examined the cytogenetics, crossing relationships, and comparative mapping of Solanum sitiens (syn. S. rickii). This tomato-like nightshade species is native to the Atacama Desert of northern Chile, and possesses traits, such as extreme drought tolerance, that could be useful to tomato breeders. The genome structure of S. sitiens and strategies to transfer its genes to tomato were studied. In order to establish the synteny of the S. sitiens genome with that of Lycopersicon spp., an interspecific F₂ mapping population from a cross between S. sitiens and S. lycopersicoides was developed. The F₁ had high fertility and normal meiosis, indicating a close affinity between these two genomes. An RFLP-based map indicated the ‘lycopersicoides’ complex (S. sitiens and S. lycopersicoides) genome is colmear with that of tomato and other Lycopersicon spp., except for a paracentric inversion on the long arm of chromosome 10. A QTL study of 19 morphological traits that segregated in the mapping population revealed 12 putative QTLs for 8 traits. To study the transmission of S. sitiens chromosomes in L. esculentum, several types of L. esculentum × S. sitiens derivatives were produced, including various aneuploids (2x + 1 to 2x + 15) and recombinant diploids. Chromosomal regions introgressed from S. sitiens were identified by molecular marker analysis using RFLPs and isozymes. Meiotic and mitotic cytology was performed to study homeologous pairing, and to determine the number of S. sitiens chromosomes transmitted to the progeny. Pollen fertility and compatibility were also evaluated in the progeny. The transfer of individual S. sitiens chromosomes into tomato and their recombination with L. esculentum homeologous was demonstrated for the first time. However, the low fertility and compatibility of intergeneric hybrids, combined with a low transmission rate of certain chromosomes, prevented a comprehensive introgression of the S. sitiens genome into tomato.