Jf. Golz et al., A molecular description of mutations affecting the pollen component of theNicotiana alata S locus, GENETICS, 152(3), 1999, pp. 1123-1135
Mutations affecting the self-incompatibility response of Nicotiana alata we
re generated by irradiation. Mutants in the M-1 generation were selected on
the basis uf pollen tube growth through an otherwise. incompatible pistil.
Twelve of the 18 M-1 plants obtained from the Mutagenesis screen were self
-compatible. Eleven self-compatible plants had mutations affecting only the
pollen function of thr S locus (pollen-part mutants), The remaining self-c
ompatible plant had a mutation affecting only the style function of the S l
ocus (style-part mutant). Cytological examination of the pollen-part mutant
plants revealed that 8 had an extra chromosome (2n + 1) and 3 did not. The
pollen-part mutation in 7 M-1 plants was followed in a series of crosses.
DNA blot analysis using probes for S-RNase genes (encoding the style functi
on of the S locus) indicated that the pollen-part mutation was associated w
ith an extra S allele in 4 M-1 plants. In 3 of these plants, the extra S al
lele was located on the additional chromosome. There was no evidence of an
extra S allele in the 3 remaining M-1 plants. The breakdown of self-incompa
tibility in plants with an extra S allele is discussed with reference to cu
rrent models of the molecular basis of self-incompatibility.