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In 1987, the NC 140 Regional Rootstock Testing Committee established sweet and sour cherry rootstock trials in 16 locations in North America. This paper will present preliminary results on the performance of Hedelfingen (sweet) and Montmoreney (sour) cherry cultivars at the New York and Michigan sites. The rootstock under test include 3 clones from Gembloux, Belgium, Colt, 4 MxM hybrids, and 9 to 13 interspecific hybrid clones from Giessen, West Germany. Clonal rootstock also under test for Montmorency include St. Lucie 64, 275 and, in New York, Holly Jolivette. Rootstock treatments differ slightly among sites and are replicated 7-8 times in a randomized complete block design. The Giessen rootstock 148/1 and 195/1 have, to date, demonstrated excellent influence on sweet cherry precocity. Sweet and sour cherry on Colt and the MxM hybrids have been most vigorous at both sites. Montmorency is most precocious on Mahaleb seedling followed by Giessen 148/1 at both locations. Data for 1990 on rootstock performance will be included in the oral presentation.
Abstract
Two-year-old apple trees growing in the nursery row were effectively defoliated by sprays of Ethrel at concentrations of 2000, 3750, and 5000 ppm. Retarded shoot growth and polarity reversal indicated that a 5000 ppm concentration was supraoptimal.
The 2000 ppm concentration somewhat delayed early spring growth, but not unacceptably so. Using this or a slightly lower level appears quite promising as a commercial practice. Development of visible root germs was greater on Ethrel treated plants.
Abstract
Rooting capacities of semihard wood cuttings from 33 Prunus fruticosa Pall, × P. avium L. and reciprocal crosses were compared under intermittent mist. Seven selections rooted with greater than 80% success, and 16 clones with less than 30% success. Roots developed from petioles of one clone.
Abstract
Degrees of resistance of 4 Malus clones to woolly apple aphid (WAA) were determined by the survival, development and behavior of nymphs caged on the plants. Nymphal survival rates after 2 weeks on ‘Empire’, ‘Northern Spy’, and ‘Robusta 5’ were 78%, 30%, and 0.8% respectively. After 4 weeks, only the aphids on ‘Empire’ were at reproductive age. M. baccata mandshurica (Maxim.) Schneid. PI 322713 ‘Manchurian Crab’ expressed partial resistance compared to ‘Empire’ on the basis of insect developmental times, even though insect survival after 2 weeks was unaffected. First instar developmental times on ‘Manchurian Crab’ and ‘Empire’ were 14 and 5 days respectively; days to reproductive maturity was greater than 30 days for ‘Manchurian Crab’ compared to 13 for ‘Empire’. Different feeding behavior was expressed by the proportion of aphids in motion at the times of observation and proportion of aphids feeding at the same location for 12-hr periods. The data suggest that for comparing quantitative differences in resistances of clones, determining developmental times is a more sensitive technique than measuring nymphal survival.
Abstract
After a severe fire blight epiphytotic, fruiting trees of rootstock cultivars were scored for kill of fruit spurs, for lesion extension, and total tree damage. Spur infections were heaviest on ‘M 9’, ‘M 12’, ‘M 16’, ‘M 25’, ‘M 26’ and ‘Rotyp’. Damage to ‘M 9’ and ‘M 26’ trees was especially severe. Least affected were ‘M 2’, ‘M 7’, ‘M 15’ and a Malus prunifolia selection, PI 286613. Intermediate susceptibility was indicated for ‘M 27’ and a red-leaved introduction from the USSR, PI 274842.
Abstract
Simazine applied to Malling-Merton (MM) 106 (Malus sp) stoolbeds at 1 kg/ha in early June + 1 kg/ha in late July had no effect on either rooting or grade of stoolshoots subsequently harvested. Application of simazine at 3 kg/ha in late July in 2 successive years reduced grades of stoolshoots, especially as percent of non-rooted shoots. The split application appeared to be suitable for commercial weed control without damage to the crop.
Abstract
Fruit finish, productivity, and tree size of 5 ‘Golden Delicious’ subclones (Malus domestica Borkh.) were compared during a 4-year period. Russeting damage greater than permitted for U.S. Fancy grade was observed in 20% of ‘Smoothee’ fruits, 55% of ‘Golden Delicious’ and 95% of each of 3 spur-type strains. No differences were observed in cumulative yield, trunk cross-sectional area, tree spread, tree height or efficiency between ‘Smoothee’ and ‘Golden Delicious’. Fruits of spur-type trees matured about 1 week later than nonspur type.
Abstract
A laboratory tank test was devised to evaluate susceptibility of 1-year-old stems of 111 Malus cultivars and hybrids to damage from pine voles (Microtus pinetorum Le Conte). This method allowed several clones to be tested at one time; provided the animals with a semi-natural environment in the laboratory; exposed each animal to all stems in the test; and required only small quantities of wood per clone. Cultivars displaying a high degree of resistance to pine vole gnawing included: Malus fusca (Raf.) Schneid. H15; M. sieboldii (Reg.) Rehd. zumi calocarpa; M. × sublobata (Zab.) Rehd. PI 286613; NY 11928 (M. pumila niedzwetzkiana (Dieck) Schneid. × M. × atrosanguinea (Spaeth) Schneid.); M. × robusta (Carr.) Rehd. No. 5 (R5); and M. yunnanensis (Franch.) Schneid. ‘Vilmorin’. Families from R5 and PI 286613 crossed with M. pumila Mill, cultivars exhibited varying degrees of vole resistance.
Abstract
The cold resistances of 14 Malus clones were determined in early March annually from 1974 to 1978. Dormant twigs were cooled at −1.8°C/hr, samples removed at 5° steps from −15 to −45°, and thawed gradually. After thawing, impedance measurements were made and the twigs were held for 16 days under intermittent mist to determine recovery. Rankings of data on growth of twigs held under intermittent mist for 16 days after thawing were similar but not identical to direct impedance values obtained immediately after thawing. Tissue damage had no evident relation to shoot diameters. Surfically discernible root germs, which were present on Mailing 7 (M 7), M 26, M 27, Malling-Merton 106 (MM 106), and Cornell-Geneva 10 (CG.10), were killed at or above −15°. ‘Empire’ and Ottawa 4 were least sensitive and ‘Katherine’ and ‘Jonagold’ most sensitive to low temperatures. The responses of M 26 to low temperatures varied widely from year to year. We could discern no relationship between hardiness in late winter and timing of spring budbreak. The growth response method reported here appears to be closely related to whole plant response under field conditions.
Abstract
Pale green lethal seedlings of apple (Malus spp.) are characterized by yellowish green color, poor growth of lateral roots, of epicotyl and of leaves, early cessation of apical meristematic activity, and death of the whole plant in about 1 month. Lethal seedlings occur in about 25% of the progeny of 2 heterozygous diploid parents. By this test we determined the homozygosity of 107 diploids (LL) and the heterozygosity of 97 diploids (LI). Among tetraploids 12 were quadriplex (LLLL) and 8 were probably duplex (LLll) or triplex (LLLl), but the expected ratios were not obtained.