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Fruit shape of four low-chill peach [Prunus persica (L.) Batsch] cultivars was evaluated in north-central, central, and southwest Florida. During 2005, measurements were taken at all locations for cheek diameter, suture diameter, and tip protrusion. A suture deformation index was calculated (suture diameter/cheek diameter) to determine suture deformation. Fruit had more protruding tips and suture deformation was more pronounced at the southwest location than at the north-central or central locations. Overall, ‘TropicBeauty’ had more protruding tips than the other cultivars. It was concluded that warmer temperatures at the southwest location during fruit development affected fruit shape by increasing the incidence of protruding tips and pronounced sutures.

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The effect of climate was observed on the relative frequency of vegetative and floral buds in four low-chill peach cultivars (‘Flordaprince’, ‘Flordaglo’, ‘UFGold’, and ‘TropicBeauty’). The trees were planted in north–central, central, and southwest Florida. The percentage of blind nodes, mixed nodes (nodes with vegetative and floral buds), and nodes with only vegetative buds were determined from three representative shoots per tree at each location. In general, higher percentages of blind nodes were observed in central and southwest Florida and higher percentages of mixed nodes were observed in north–central Florida. ‘TropicBeauty’ tended to have a greater percentage of blind nodes than the other cultivars. Higher temperatures during bud formation most likely contributed to the increased amounts of blind nodes observed in the central and southwest locations and to the reduced amounts of mixed nodes. However, stresses imposed by bacterial spot and hurricanes may have contributed to the higher incidence of blind nodes in 2005. Our results indicate that certain genotypes have a predisposition for the formation of blind nodes. Advanced selections having low chilling requirements and potentially being adapted to a wide diversity of tropical or subtropical climates need to be tested in multiple locations to evaluate blind node formation.

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Blueberry (Vaccinium spp.) summer pruning can increase yield by promoting healthy fall foliage to support the reproductive development. However, there has been little research to examine the effects of timing and intensity of summer pruning in subtropical conditions. The objective of this study was to determine the effects of summer pruning timing and intensity on reproductive traits of mature ‘Jewel’ and ‘Emerald’ southern highbush blueberry (SHB) plants (V. corymbosum L. interspecific hybrid) in subtropical Florida. The effect of pruning time was evaluated by removing 30% of the canopy in June or July. The effect of intensity was evaluated by pruning either 30% or 60% of the canopy in June, followed by removal of the upper 5 cm of regrowth (“tipping”) in July. Both timing and intensity used nonpruned plants as a control. The same plants were evaluated over three consecutive seasons (June 2011–May 2014). Main effects of pruning time, intensity, and tipping were evaluated. Tipping did not affect the reproductive traits evaluated. ‘Emerald’ reproductive traits were unaffected by either summer pruning time or intensity over the 3-year study. ‘Jewel’ yield was unaffected in the first year, but was increased by 48% and 65% in years 2 and 3, respectively, in the 30% pruning treatment compared with the nonpruned control. Lack of pruning in ‘Jewel’ decreased inflorescence bud number compared with moderate pruning likely due to more diseased foliage that increased defoliation. Thus, pruning effects on reproductive traits were cultivar dependent. Leaving ‘Jewel’ plants unpruned for two or more seasons reduced inflorescence bud number and yield.

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Field performance of southern highbush blueberry (Vaccinium corymbosum L. interspecific hybrids) cultivars Emerald, Jewel, and Primadonna derived from softwood cuttings (SW) and tissue culture (TC) was evaluated in Citra and Haines City, FL, in 2010–12. Both fields were planted in Apr. 2010 on sandy soil amended with pine bark. Plant height and width were recorded at both locations, from which plant canopy volume was calculated. Additionally, whole plants were harvested at planting and after the first growing season, after the first fruit harvest, and after the second growing season. Average plant height and width, number of major canes, and total shoot number were determined at each sampling date. Dry weights for roots, crowns, canes, shoots, and leaves were obtained. Although propagation method affected plant canopy volume during the first season, no effects were observed by the end of the second growing season. At planting and after the first and second growing seasons, TC plants of the three cultivars had more major canes. Total shoot number per plant was greater for TC ‘Jewel’ at all dates but ‘Emerald’ TC plants had more shoots only at planting and after the first growing and harvest seasons. Tissue culture resulted in increased plant dry weights of ‘Jewel’ and ‘Emerald’ after the first and second growing seasons. There were no significant differences in total number of shoots or plant dry weight between TC and SW-derived ‘Primadonna’ plants at any point during the study.

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Vaccinium arboreum Marsh is a small tree adapted to low-organic matter soils and is one of the few ericaceous species that tolerates soil pH greater than 6.0. It has a deep root system and is more drought tolerant than cultivated blueberry. The use of V. arboreum as a rootstock for commercial blueberry production has been studied previously in young blueberry plantings. The objective of the current study was to expand on earlier work and evaluate growth, productivity, and tolerance to bacterial leaf scorch (Xylella fastidiosa) in established plantings of own-rooted vs. grafted southern highbush blueberry (SHB). Two field plantings of grafted and own-rooted ‘Meadowlark’ and ‘Farthing’ SHB were established in May 2011: one at the University of Florida–Institute of Food and Agricultural Sciences (UF-IFAS) Plant Science Research and Education Unit in Citra, FL, and the other at a commercial blueberry farm in Archer, FL. At both sites, four rootstock–scion combinations were grown in either pine bark-amended or nonamended soil. Canopy volume was greater in grafted compared with own-rooted ‘Meadowlark’ at both locations throughout the 4 years of the study (2015–18), whereas canopy volume in ‘Farthing’ was not consistently different. For both cultivars and both locations, canopy volume was greater on amended compared with nonamended soil. Although canopy growth was not consistently increased in the grafted compared with own-rooted plants, yield was greater in grafted plants of both cultivars at both locations. Cumulative yield over the 4 years was similar between grafted plants grown on both amended and nonamended soil, and was significantly greater than yield of own-rooted plants on nonamended soil, suggesting the use of this rootstock may decrease the requirement for pine bark amendment. In general, grafted plants produced larger berries, with no negative impacts on fruit soluble solids, titratable acidity, or firmness. ‘Meadowlark’—an SHB cultivar that exhibits high sensitivity to bacterial leaf scorch—displayed decreased development of bacterial leaf scorch symptoms when grafted onto V. arboreum compared with own-rooted plants. These results indicate the potential benefits of grafting SHB onto V. arboreum rootstock, particularly under marginal soil conditions. However, a complete economic analysis that also takes into account any differences in longevity between the two systems must be done to determine whether the benefits of using grafting are feasible financially for the grower.

Open Access

The profitability of the fresh market blueberry industry in many areas is constrained by the extensive use and cost of soil amendments, high labor requirements for hand harvesting, and the inefficiencies of mechanical harvesters. Vaccinium arboreum Marsh is a wild species that has wide soil adaptation and monopodial growth habit. It has the potential to be used as a blueberry rootstock, expanding blueberry production to marginal soil and improving the mechanical harvesting efficiency of cultivated blueberry. The objectives of this research were to compare yield, berry quality, and postharvest fruit storage of own-rooted vs. grafted southern highbush blueberry (SHB) cultivars (Farthing and Meadowlark) grown on amended vs. nonamended soil and either hand or mechanical harvested. Yields of hand-harvested SHB during the first two fruiting years were generally greater in own-rooted plants grown on amended soil compared with own-rooted plants on nonamended soil or grafted plants on either soil treatment. However, by the second fruiting year, hand-harvest yields of grafted SHB were ≈80% greater than own-rooted plants when grown in nonamended soil. Yields of mechanical-harvested SHB grafted on V. arboreum and grown in either soil treatment were similar to yields of mechanical-harvested own-rooted plants in amended soil the second fruiting year, and greater than yields of own-rooted plants in non-amended soil. In general, mechanical harvesting reduced marketable yield ≈40% compared with hand harvesting. However, grafted plants reduced ground losses during harvest by ≈35% compared with own-rooted plants for both cultivars. Mechanical-harvested berries had a greater total soluble solids:total titratable acidity ratio (TSS:TTA) than hand-harvested berries, and berries harvested toward the end of the harvest season had a greater TSS:TTA than those from early-season harvests. As postharvest storage time increased, berry appearance ratings decreased and berry softness and shriveling increased, particularly in mechanical-harvested compared with hand-harvested berries. Firmness of mechanical-harvested berries decreased during storage, whereas firmness of hand-harvested berries remained relatively stable. However, fruit quality at harvest and during postharvest storage was unaffected by V. arboreum rootstocks or lack of pine bark amendment. This study suggests that using V. arboreum as a rootstock in an alternative blueberry production system has the potential to decrease the use of soil amendments and increase mechanical harvesting efficiency.

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Pruning is a recommended practice for blueberry (Vaccinium spp.) production and is usually done in the summer in warm subtropical climates with long growing seasons. Summer pruning promotes healthy vegetative growth during the remainder of the growing season; however, research-based recommendations for summer pruning strategies are lacking. The objective of this study was to determine effects of summer pruning timing and intensity on vegetative growth in ‘Jewel’ and ‘Emerald’ southern highbush blueberry (V. corymbosum-interspecific hybrid), two cultivars of the primary species grown in subtropical areas. To determine effects of pruning time, 30% of the canopy was removed in June or July. To determine pruning intensity effects, either 30% or 60% of the canopy was removed in June, both followed by shoot tipping in July. Both timing and intensity treatments were compared with a non-pruned control. Lack of pruning in the first year had no negative effects on growth; however, lack of pruning for two or more seasons decreased regrowth volume and shoot length of both cultivars. By the third season, canopy regrowth volume in both cultivars decreased in the non-pruned control compared with the 30% and 60% pruning treatments and compared with the June pruning treatment. Disease infection in ‘Jewel’ was also increased in the non-pruned control compared with these pruning treatments. Summer pruning, regardless of timing or intensity, generally increased vigor of vegetative growth for both cultivars and decreased incidence of leaf disease in ‘Jewel’.

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Vaccinium arboreum Marsh is a wild species adapted to high pH (above 6.0) and low organic matter soils (below 2.0%). The use of V. arboreum rootstocks may be a viable option to increase soil adaptation of southern highbush blueberry (SHB) (Vaccinium corymbosum interspecific hybrid) under marginal soil conditions. The objective of this research was to evaluate the vegetative and reproductive traits of ‘Farthing’ and ‘Meadowlark’ SHB own-rooted or grafted onto V. arboreum and grown in pine bark–amended or nonamended soil. The study was conducted from 2012 through 2014 at a research center in Citra, FL, and a grower’s farm in Archer, FL. Vaccinium arboreum rootstock generally induced the same effects in both cultivars. Grafted plants in both soil treatments had reduced canopy growth in the first year after field planting compared with own-rooted plants in amended soil. However, canopy volume of grafted plants was greater than own-rooted plants in nonamended soil and similar to own-rooted plants in amended soil 2 years after field planting for ‘Meadowlark’ and 3 years after planting for ‘Farthing’. Fruit yield was lower in grafted plants compared with own-rooted plants in the first fruiting year (2 years after field planting). By the second fruiting year, yields of grafted plants were similar to or greater than yields of own-rooted plants when grown in nonamended soil, whereas in amended soil, yields of grafted plants were similar to yields of own-rooted plants. Grafted plants had greater mean berry weight, but lower berry firmness; however, the firmness values were still considered acceptable (greater than 160 g⋅mm−1). Internal fruit quality [total soluble solids (TSS) and total titratable acidity (TTA)] was not consistently affected by the rootstock or soil treatments. These results suggest that grafting SHB onto V. arboreum does not increase yield in the establishment years compared with own-rooted SHB when grown in amended soils, but may have the ability to increase yield with no negative effects on fruit quality when grown in nonamended soils.

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Southern highbush blueberry (Vaccinium corymbosum interspecific hybrid) cultivation is a major industry in subtropical regions where low winter temperatures are infrequent and inconsistent. In Florida and other subtropical areas, growers use hydrogen cyanamide (HC) applications during endodormancy to mitigate the negative effects of low chill accumulation. Hydrogen cyanamide is a synthetic plant growth regulator that increases and expediates dormancy release and budbreak. However, southern highbush blueberry cultivars differ in their sensitivity to HC. Optimus and Colossus are two recently released cultivars from the University of Florida blueberry breeding program. The effects of HC in these cultivars are unknown. This research aimed to describe responses to HC applications at different rates for these new varieties. Experiments took place in a commercial farm in Waldo, FL, on 3- to 4-year-old deciduous blueberry bushes. HC was applied at rates of 3.8 g·L−1 (0.38%), 5.1 g·L−1 (0.50%), and 6.4 g g·L−1 (0.63%) in ‘Optimus’ and 3.8 g·L−1 (0.38%), 5.1 g·L−1 (0.50%), 6.4 g·L−1 (0.63%), and 7.7 g·L−1 (0.75%) in ‘Colossus’. In both cultivars, the control treatment was not sprayed. Vegetative bud count, and flower bud development, flower bud mortality, and yield were determined. HC application thinned reproductive buds and increased vegetative budbreak. Although seasonal yield was not increased, HC advanced fruit ripening early in the season.

Open Access

Like everything for the past 2 centuries, agriculture has depended increasingly on fossil fuel energy. Pressures to shift to renewable energy and changes in the fossil fuel industry are set to massively alter the energy landscape over the next 30 years. Two near-certainties are increased overall prices and/or decreased stability of energy supplies. The impacts of these upheavals on specialty crop production and consumption are unknowable in detail but the grand lines of what will likely change can be foreseen. This foresight can guide the research, extension, and teaching needed to successfully navigate a future very unlike the recent past. Major variables that will influence outcomes include energy use in fertilizer manufacture, in farm operations, and in haulage to centers of consumption. Taking six increasingly popular fruit and vegetable crops and the top two horticultural production states as examples, here we use simple proxies for the energy requirements (in gigajoules per ton of produce) of fertilizer, farm operations, and truck transport from Florida or California to New York to compare the relative sizes of these requirements. Trucking from California is the largest energy requirement in all cases, and three times larger than from Florida. As these energy requirements themselves are all fairly fixed, but in future will likely rise in price and/or be subject to interruptions and shortages, this pilot study points to two commonsense inferences: First, that fruit and vegetable production and consumption are set to reposition to more local/regional and seasonal patterns due to increasing expenses associated with fuel, and second, that coast-to-coast produce shipment by truck will become increasingly expensive and difficult.

Open Access