Few Cytoplasm Contribute to North American Strawberry Cultivars

Abstract

The cytoplasm of plants contains genetic information that is transmitted maternally. All progeny from a single female plant will share the same extra-chromosomal genes unless a mutation occurs. To date, the strawberry (Fragaria × ananassa Duch.) has not been analyzed to show the cytoplasmic contribution of different maternal founding clones to the gene pool of North American cultivars. This report summarizes the contribution played by the maternal founding clones to the cytoplasm. of the present North American cultivars. The 134 cultivars of known parentage released in North America between 1960 and 1987 were used as the database, and the pedigree tables assembled by Sjulin and Dale (1987) were used as the basis for this study. The cytoplasm of each cultivar was traced by following pedigrees back to the original maternal parent or the last clone of known parentage. Only 17 cytoplasm were identified in the 134 cultivars of known parentage (Table 1), considerably fewer than the 53 founding clones identified by Sjulin and Dale (1987). Three of the cytoplasm were traced to their native founding clones, while the others were traced to old cultivars whose origins could not be determined due to incomplete records. Therefore, there are almost certainly even fewer cytoplasm involved than 17. The exact number of founding cytoplasm could probably be inferred from assays of the mitochondrial and chloroplast DNA. Cultivars with a single cytoplasm were sorted into 11 groups based on geographical origin (Sjulin and Dale, 1987) to see if the groups contained few or unique cytoplasm. The contribution of the cytoplasm varied among these groups. Those of ‘Missionary’ and ‘Hudson Bay’ are evenly distributed, each in six of the 11 groups, whereas the cytoplasm of ‘Middlefield’ (13/18 in California