A method for shoot regeneration from leaf explants in two cultivars of cranberry (Vaccinium macrocarpon Ait.) is described. Modified Anderson's medium supplemented with combinations of thidiazuron (TDZ) with or without 1 luM NAA (a-naphthaleneacetic acid) was used to optimize shoot regeneration. The effect of light or dark incubation was also determined. Maximum regeneration was obtained in the light in the presence of 10 ~M TDZ and 1 IJ-M NAA. While this medium was suitable for leaf explants obtained from shoot cultures, regeneration did not occur from leaves collected from greenhouse-grown plants. Elongation of the regenerated shtSot tips did not occur until explants were transferred to growth regulator-free medium at which time only a minority of shoots elongated. Elongated shoots could be dissected away from leaf tissue, rooted easily, and acclimitized to ambient conditions.Abbreviations: NAA -a-naphthaleneacetic acid; TDZ -1-phenyl-3-(1,2,3 -thiadiazol-5-yl) urea

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Lycopersicon peruvianum is a wild species of tomato that exhibits gametophytic self-incompatibility (S), wherein the SI response is controlled by the genotype of the pollen. Cultivated tomato (L. esculentum) is a self-compatible species. Assisted by phenotypic markers, periclinal graft chimeras between these two species have been obtained. Fruit set analysis following breeding demonstrated that the available five chimeras (PPE, PEE, PEP, EPP, and EEP) are able to accept pollen from L. peruvianum, suggesting that there is a failure of the SI response. SI response is known to be dependent on S-locus associated proteins. These proteins are present in the style, which is mainly derived from the L1 and L2 layers of meristem. RNA analysis of the style tissue using a cloned S-locus cDNA as a probe showed that, except for EEP, all chimeras expressed the S-allele. This was also confirmed by SDS-PAGE analysis of stylar proteins that were present in variable amounts depending on the periclinal combination. Thus, the breakdown of SI is not associated with the lack of expression of the S-locus. Further work is being conducted to understand the nature of this breakdown.