Mother block plantings of 6 cultivars of highbush blueberry (Vaccinium corymbosum L.) for the production of cutting wood were successfully grown at 30.5 × 30.5 cm spacings on a Berryland soil. At this spacing 4- and 5-year-old ‘Bluecrop’ plants produced at the rate of 5.27 million cuttings per ha. Cutting wood production increased with increasing N fertilization. Optimum rate of N application was in excess of 45 kg N/ha. Application of fungicide under certain conditions increased weight per cutting.
Increasing the rate of N application and the spacing distance between potted 3-year-old highbush blueberry (Vaccinium corymbosum L.) plants ‘Earliblue’ increased fruit production and promoted early ripening. The increased N rate was associated with increased vegetative growth and berry size, whereas the increased plant spacing was associated with an increase in flower bud formation and flower number.
Resistance to blighting by Monilinia vaccinii-corymbosi (Reade) Honey was evaluated under greenhouse conditions in multiple populations of the diploid species Vaccinium boreale Hall & Aalders, V. corymbosum L., V. darrowi Camp, V. elliottii Chapm., V. myrtilloides Michx., V. myrtillus L., V. pallidum Ait., and V. tenellum Ait., as well as in accessions of the polyploid species 4x V. hirsutum Buckley and 6x V. corymbosum f. amoenum Aiton. Significant species differences were found in mean blighting levels averaged over 2 years, with values ranging from 3.5% for V. boreale to 49.2% for 2x V. corymbosum, compared with 27.5% for the resistant 4x V. corymbosum check, `Bluejay', and 64.3% for the susceptible 4x V. corymbosum check, `Blueray'. Wild Vaccinium species may serve as new sources of resistance to blighting, if resistance can be transferred easily and horticultural type recovered.
Sixty-eight highbush blueberry (Vaccinium corymbosum L.) cultivars and selections were evaluated over 3 years for their resistance to the fruit infection phase of mummy berry disease [Monilinia vaccinii-corymbosi (Reade) Honey]. Average incidence of fruit infection under test conditions was 34.3% in 1995, 14.4% in 1996, and 27.9% in 1997, with significant differences occurring among clones in all 3 test years. Several cultivars exhibited consistent resistance to mummy berry fruit infection across all years of testing. `Northsky', `Reka', `Northblue', `Cape Fear', `Bluegold', `Puru', and `Bluejay' were among the most resistant, and `Atlantic', `Berkeley', `Herbert', and `E-176' were among the most susceptible. The consistent resistant reaction of certain cultivars indicates that they may be suitable as parents for introducing resistance into a breeding program. No significant correlation was observed between blighting resistance and fruit infection resistance.
The resistance of 26 rabbiteye blueberry (Vaccinium ashei Reade) cultivars to the blighting phase of mummy berry disease was evaluated under controlled conditions. In 1997, blight levels ranged from 31% to 84%, and averaged 61.3% across all cultivars. In 1998, blight levels ranged from 71% to 99%, and averaged 89.9%. Several cultivars, including `Coastal', `Delite', `Centurion', `Walker', `Callaway', and `Garden Blue', exhibited significantly lower levels of mummy berry blight infection in both years. Blighting levels were significantly correlated with new shoot length in 1997, but not in 1998. Rabbiteye blueberry, in general, is less resistant to mummy berry blight than is highbush blueberry (V. corymbosum L.), but several options exist for potential improvement.
More fungal rot developed in storage of water-picked (WP) than in hand-picked (HP) fruit of cranberry (Vaccinium macrocarpon Ait) after the berries had been held in the bog water up to 24 hours. When the water-immersion time was 12 hours or more, more physiological breakdown (PB) occurred in HP than in WP fruits. Generally, less rot and PB developed in the most highly colored berries (dark red) than in berries that were less colored.
Six cranberry (Vaccinium macrocarpon Ait.) cultivars, (water harvested under New Jersey growing conditions) were evaluated for their suitability for fresh market sale. Fruit were hand-picked and water-reel picked, held in the bog flood water for 0-, 4-, 8-, 12-, and 24-hr periods, and then stored for 12 weeks at 3°C. After an additional 4 days at 21° storage the fruit were evaluated for fungal fruit rot and physiological breakdown (PB). ‘Franklin’, ‘Pilgrim’, and ‘Stevens’ were superior to ‘Early Black’ and ‘Wilcox’ as measured by occurrence of rot and PB. Water immersion time had a greater influence on PB than on rot. As time in the water increased, the percentage of fruit manifesting PB increased, with ‘Ben Lear’ developing the least and ‘Early Black’ and ‘Wilcox’ the most PB.
A group of 1031 genotypes representing 245 different crosses from a joint U.S. Dept. of Agriculture-New Jersey Agricultural Experiment Station blueberry breeding program was evaluated for blueberry red ringspot virus (BBRRSV) symptoms after 8 years of field exposure. Among 41 parents represented by 10 or more progeny, significant differences were observed in offspring BBRRSV expression. The species Vaccinium lamarckii Camp. (4x) and V. amoenum Ait. (6x) and the cultivars Woodard (6x) and Earliblue (4x) seem to have high frequencies of alleles for BBRRSV resistance. Significant differences were also found among 21 different crosses. The most resistant cross was `Elizabeth' x `Earliblue', which had a 23% BBRRSV incidence. Progeny evaluation revealed that none of the parents involved produced families in which all plants were resistant; hence, resistance to this virus may be under polygenic control.
A clone of the diploid blueberry species Vaccinium atrococcum Heller, was previously found to be highly resistant to the fungus tetraploid highbusy blueberry. The tetraploid V. atrococcum was highly root-rot resistant in a greenhouse study. It was crossed with ‘Earliblue’ and 85 seedlings were obtained. In general, the seedlings were fertile, had small, dark fruit with mild flavor, good scars and quite soft flesh consistency.
Blueberry selections Me-US 32 and Michigan Lowbush 1, and cultivars ‘Berkeley’, ‘Bluecrop’, ‘Earliblue’, and ‘Dixi’ were screened in the greenhouse for resistance to P. cinnamomi. Michigan Lowbush 1 was highly resistant to the root-rot fungus. Me-US 32 was resistant, but all the cultivars were susceptible. Michigan Lowbush 1 is a grandparent and probably the source of resistance of Me-US 32.
In vitro conidia production by Monilinia vaccinii-corymbosi (Reade) Honey, the cause of mummy berry disease in blueberry, was significantly enhanced by cellulose acetate membranes placed on the surface of V-8 juice agar for most of the pathogen isolates tested, compared to V-8 juice agar alone. Temperature and light affected conidia production, but the effects were not consistent. Higher temperature (22 vs. 15 °C) yielded better sporulation, but the effects of light environment were variable. When 55 isolates from various sources were rated visually for sporulation on cellulose acetate membranes at 22 °C under ambient light/dark cycles, a wide range of conidium production was observed, and three of 55 isolates (6%) were identified as having very high conidia production.