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  • Author or Editor: D. O. Ketchie x
  • Journal of the American Society for Horticultural Science x
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Abstract

The croprotectants, polyvinylpyrolidone, glycerol, ethylene glycol and dimethyl sulfoxide were applied individually or in combination with each other in the form of a spray on whole apple (Malus domestica Borkh.) trees in the greenhouse and by terminal feeding apple and pear (Pyrus communis L.) trees in the field. The trees were tested both by artificial and natural freezing. The cryoprotectants increased cold resistance, however, different cultivars showed different effects with the various protective agents. Factors other than the colligative properties appeared to modify the effects of cryoprotectants.

Open Access

Abstract

Spur wood and spur bark of ‘Delicious’ apple (Malus domestica Borkh.) trees affected by dead spur disorder (DS) grew more vigorously than those of healthy (CK) trees the first 2 years. Buds were smaller on DS than on CK trees. Leaves were smaller on DS than on CK trees on 2-year-old and older limb sections. DS trees produced most fruit on 2-year-old limb sections, whereas CK trees produced most fruit on 3-year-old limb sections. Length and diameter growth of the limbs was unaffected, but the internode length was shorter on DS than on CK trees. Death of the spurs was preceded by bud failure in the spring.

Open Access

Abstract

Cold resistance of current season shoots and trunk bark of ‘Red Delicious’ apple trees were compared with seasonal temperature through 4 winters. Cold resistance was measured by electrolytic conductance and recorded as T10 and T90. There was correlation between cold resistance and the temperature during 7 days preceding cold acclimation measurement. Sustained temperature below 0°C increased cold resistance more than did very low temperature interrupted by short periods above freezing.

Open Access

A cooperative experiment begun in 1980 was designed to evaluate the productivity and other characteristics of 16 spur and 12 standard strains of `Delicious' apple on two rootstocks (M.7 EMLA and MM.111 EMLA). All trees were propagated at one nursery, and plantings were established in Michigan, Washington, Oregon, Idaho, Indiana, and British Columbia. In Michigan, trees of standard strains were consistently larger than trees of spur strains 8 years after planting. Early yields were greater on M.7 EMLA than on MM.111 EMLA, but trees were more subject to leaning under heavy crops on M.7 EMLA. In general, spur-type strains yielded more fruit per unit trunk cross-sectional area than standard strains. Yield was more closely associated with fruit-setting ability than with flower density, and fruit size declined as fruit set increased. Length/diameter ratios and biennial bearing indices also differed significantly among strains.

Free access

Abstract

Electrolytic conductance was measured from acclimated and nonacclimated seedlings of apple, pear and citrus which were frozen and unfrozen. A close correlation between electrolytic conductance and survival was shown. A comparison was made between conductance and injury of apple and pear trees in the natural freeze of 1968-69 in Washington. Procedures are outlined for using conductance as a measure of cold tolerance among cultivars or treatments within the same cultivar. The use of T10 and T90, which describes the transition range of injury, is outlined and described. Procedures are also outlined for following acclimation or deacclimation through the year and for determining freeze-injury from natural freezes.

Open Access