Effects of segments of chromosome 1 and 3 from L . hirsutum (LA1777) on anther and style length in L . esculentum background Weiner, J . L . , Bernatzky, R . Department of Plant and Soil Sciences, University of Massachusetts, Amherst, MA 01003 The major locus controlling self - incompatibility ( S - locus) is located on the short arm of chromosome 1 .   We have introgressed chromosome 1 segments from self - incompatible L . hirsutum (LA1777) into L . esculentum cv Vendor by marker - assisted selection to study the effects on self - fertility in cultivated tomato .   Although the S - locus alone is not sufficient to establish self - incompatibility in L . esculentum (Bernatzky et al . 1995), we have used these partial substitution lines to screen for other chromosome segments that, in combination with the S - locus, reduce self - fertility .   We have identified a region of chromosome 3 that greatly reduces self - fertility in the presence of the S - locus in greenhouse grown late generation backcross material (unpublished) .    We have also examined this material for effects on flower morphology, specifically stigma exsertion .   We measured anther length and style and stigma length on two BC7 plants containing a chromosome 1 segment bearing the S - locus of L . hirsutum from RFLP markers CT197 to CT231 (approximately 36 cM) and a chromosome 3 segment from CT118B to Rbcs2 (approximately 8 cM) .   We also measured flowers of the original parents, cv Vendor and an individual of L . hirsutum (LA1777) .   The average of 12 measurements of cv Vendor, LA1777, and 12 each of the two BC7 individuals (data combined) was as follows:   Genotype Style and Stigma Anther Vendor 7 . 33   +   0 . 44 9 . 55   +   0 . 25 BC7 7 . 98   +   0 . 34 9 . 97   +   0 . 80 LA1777 10 . 29   +   0 . 58 9 . 58   +   0 . 32 Both anther ( a = 0 . 05) and style and stigma ( a = 0 . 001) lengths differ significantly for all three genotypes .   However, the stigmas of cv Vendor and the BC7 individuals are well contained within the anther cone .   This data suggests that, at least in the heterozygous condition, these chromosome 1 and 3 segments from LA1777 do not cause stigma exsertion in the cv Vendor background . Literature cited: Bernatzky, R . , R . H . Glaven and B . A . Rivers .   1995 .   S - related protein can be recombined with self - compatibility in interspecific derivatives of Lycopersicon .   Biochemical Genetics 33:215 - 225 .