The degree of relationships within Lactuca sativa and three wild relatives L. serriola, L. saligna, and L. virosa was studied by observing the performance, vigour and fertility of the F 1 hybrids obtained from crosses made in and between the four species. The crosses of L. saligna ×L. virosa and the reciprocal crosses produced no hybrids. L. saligna and L. virosa are the least related of the four species. L. sativa ×L. serriola and the reciprocal crosses were successful and produced fertile hybrids These two species are genetically very closely related. L. saligna is known to produce, as a female parent, hybrids with L. sativa and L. serriola. Now the reciprocal cross was successful for the first time, so the unability to obtain hybrids in the past was based on the choice of accessions and not caused by unilateral incompatibility. L. virosa ×L. sativa and the reciprocal combination produced hybrids. The combination L. serriola ×L. virosa produced hybrids with very limited fertility. In contrast to earlier reports (sterile hybrids) one combination of the reciprocal cross too produced hybrids with very limited fertility.-Some of the L. saligna ×L. sativa (and reciprocal) hybrids were found to look strikingly like L. serriola. This adds evidence for the descent of L. serriola and L. sativa:L. saligna also made part of the ancestral complex of the cultivated lettuce. © 1990 Springer-Verlag.
