HortScience 140:551-552. August 1979.
'Jonafree' Apple1D. F. Dayton and J. B. Mowry
Department of Horticulture, University of Illinois, Urbana, IL 61801
E. B. Williams1, Jules Janick3, and F. H. Emerson3
Purdue University, West Lafayette, IN 4 790 7
L. F. Hough and Catherine Bailey
Department of Horticulture and Forestry, Rutgers, The State University, New Brunswick, NJ 08903
Additional index words: Malus spp., fruit breeding, disease resistance
1Received for publication March 26, 1979. This research was partially supported by funds from the Illinois Agricultural Experiment Station and from the Purdue University Agricultural Experiment Station. Journal Paper No. 7568 of the Purdue University Agricultural Experiment Station. Paper of the journal series of Cook College, Department of Horticulture and Forestry, Rutgers, The State University.
'Jonafree' is an attractive red apple (Malus domestia Borkh) with field immunity to apple scab incited by Venturia inaequalis (Cke) Wint. The fruit is of medium size and matures with 'Jonathan'. It is released as a potential commercial cultivar with strong resemblance to 'Jonathan' in many major horticultural characters in addition to its similar maturity date.
'Jonafree' is the 5th apple cultivar (1, 2, 3, 4) developed by the cooperative apple breeding program of the Illinois, Indiana, and New Jersey Agricultural Experiment Stations. It appears best adapted to those climatic regions which favor good development of 'Jonathan'. The attractive glossy red fruit closely resembles 'Jonathan' in size and shape (Fig. 1). The medium red overcolor covers up to 95% of the fruit surface, but when allowed to become full ripe on the tree does not develop the very dark red characteristic of some 'Jonathan' strains.
Fig. 1. Fruits of 'Jonafree'
The skin is moderately thick and tough, very similar to 'Jonathan'. The flesh is pale yellow, fine grained, crisp and juicy. Fruits directly from the tree at maturity are somewhat less acid than 'Jonathan', but with a rich and slightly aromatic flavor. The dessert quality is classified as very good.
Fruit of 'Jonafree' in ordinary storage at 0.5-1.0°C hold texture and flavor up to 10 weeks. Shriveling due to moisture loss, even without humidification, does not occur. "Jonathan spot" or similar disorders, even on very overripe fruits or after long storage, have not been observed.
While field immune to apple scab, 'Jonafree' appears slightly susceptible to apple mildew incited by Podosphaera leucotricha (Ell. & Eu.) Salm., but networks of russet on the fruit have not been observed. The few fireblight infections incited by Erwinia amylovora (Burrill) Winslow et al. observed on new shoots failed to advance into older wood, indicating much lower susceptibility than 'Jonathan'.
The original seedling tree was planted in 1965 in a breeding orchard of the Illinois Agricultural Experiment Station, Urbana, Illinois. The seedling resulted from crossing an earlier seedling selection 855-102 as seed parent with New Jersey 31 as pollen parent. The complete pedigree is shown in Fig. 2. It was selected on the basis of its fruit characteristics in 1972. Propagated trees have been and are under test, as Coop 22, at the cooperating agricultural experiment stations and at several locations in the respective states.
Fig. 2. Pedigree of 'Jonafree' apple.
The tree is vigorous and sets heavy annual crops, indicating that thinning may be necessary in years when pollination conditions are favorable. The growth habit is moderately spreading, not a "spur type", but the fruit is borne almost entirely on spurs. Spur production on grafted trees is heavy, and grafted trees have been as precocious as 'Jonathan' is bearing. It appears compatible on Malling (M) 7 and M 9 rootstocks.
The following detailed description follows Zielinski (5), and uses color designations according to the 1966 Royal Horticultural Society Colour Chart, issued by the Royal Horticultural Society of London.
TREE AND FOLIAGE
Propagation material for test purposes is available to state and federal agricultural experiment stations. Trees will be available from qualified nurseries. An application for a plant patent has been filed.