Identification, transmission, and cytological behavior ofSolanum lycopersicoidesDun. monosomic alien addition lines in tomato (Lycopersicon esculentumMill.)

Abstract

The wild nightshade Solanum lycopersicoides possesses a number of disease- and arthropod-resistance and environmental stress tolerance traits of potential value for the cultivated tomato, Lycopersicon esculentum. F1hybrids are readily obtained by sexual crosses, but backcrosses to tomato are hindered by sterility and incompatibility barriers. In the present studies, intergeneric sesquidiploid hybrids (2 genomes of L. esculentum and 1 of S. lycopersicoides) were pollinated with Lycopersicon pennellii derived bridging lines, yielding diploid, aneuploid (up to 2n + 6), and polyploid (3x, 4x) progeny. After diploids (58% of total progeny), the group most frequently obtained was 2n + 1 (31%), which included all 12 possible monosomic alien addition lines (MAALs) containing a single extra chromosome from S. lycopersicoides in a tomato background. MAAL groups were identified with a combination of allozyme, RFLP, and monogenic visual markers. Transmission rates of the extra chromosomes in MAALs varied from 0%, for chromosome 6, to 24%, for chromosome 10. At diakinesis and metaphase I of meiosis, the alien chromosome was usually unpaired (in an average of 90% of PMCs), but association of homoeologous chromosomes was observed in each of the 12 MAAL groups (in an average of 5.7% of PMCs). The MAALs showed a striking morphological resemblance to the corresponding tomato primary trisomic. In addition, each MAAL expressed S. lycopersicoides specific leaf, flower, and (or) fruit characters. This set of MAALs, the first of its kind in Lycopersicon, is expected to be useful for a variety of gene-mapping and introgression studies.