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Research Bulletin (Iowa Agriculture and Home Economics Experiment Station)

Abstract

Two hundred seventy-three Jonathan seedlings produced by 11 crosses form the basis of the records in this bulletin.

These studies show clearly that the progenies produced by the different crosses of Jonathan differ or vary in many important characteristics. These variations are attributed to differences in the genetic constitution of the several varieties which were used in combination with Jonathan, and indicate the relative value of these varieties as parents when crossed with Jonathan.

The range of variation in the seedlings of these progenies is generally quite wide both as to tree and fruit. Differences in the horticultural characteristics such as occur in size, form, color, flavor, quality and season of the seedling fruits suggest that multiple factors are concerned, which produce the many variations observed.

Jonathan appears to carry as partially dominant factors for medium and below medium size of fruit, but it evidently carries factors also for large and for small size. Factors for roundish, conic, oblate and oblong fruit forms are present. Jonathan appears to be homozygous for red skin color but is heterozygous for pattern and carries factors for both fine and coarse grained flesh, for juiciness, for both acid and sweet flavor and for very good as well as for poor quality. The factors which control the season of the fruit are evidently complex. Jonathan appears to carry factors for season varying from late summer to late winter but probably carries as dominant the factors for mid-winter season.

It is of importance to observe that the color, size and flavor of Jonathan were recovered occasionally and that these characteristics were combined with the characteristics of the other parent variety.

Colorado Orange produced a higher percentage of fruits of good commercial size than did Salome, Anisim or Roman Stem when crossed with Jonathan. When crossed with Jonathan, Salome produced the highest percentage of fruit rating good and very good, followed in order by Colorado Orange, Anisim and Roman Stem. Late season appeared most often in the seedlings of Colorado Orange and Salome, while Anisim and Roman Stem produced no late season apples. The value of crossing two red apples is shown by the high percentage of good red seedling fruits produced by Anisim and Wealthy when crossed with Jonathan. It is interesting to note that Colorado Orange and Roman Stem produced a high percentage of seedling fruits which were deficient in good red color.

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