Effects of Timing and Intensity of Summer Pruning on Reproductive Traits of Two Southern Highbush Blueberry Cultivars

Abstract

<jats:p>Blueberry (<jats:italic>Vaccinium</jats:italic> 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 (<jats:italic>V. corymbosum</jats:italic> 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.</jats:p>

Vegetative and Reproductive Traits of Two Southern Highbush Blueberry Cultivars Grafted onto Vaccinium arboreum Rootstocks

“…The high levels of Ca and bicarbonate found in the irrigation water in Archer, combined with the transient increase in soil pH (6.0-6.3) from Feb. to July 2013, decreased plant growth, particularly in nonamended soils. The reduced canopy volume may decrease availability of carbohydrates for fruit development (Maust et al, 1999), potentially decreasing berry weight, supporting work by Kovaleski et al (2015), who reported reduction in mean berry weight in plants that had 60% of the canopy removed compared with nonpruned plants.…”

“…Mean berry weight varied considerably between field locations and cultivars. Previous work report differences in mean berry weight due to different factors, such as pruning (Kovaleski et al, 2015), seed number per berry (Harrison et al, 1993), source:sink ratio (Maust et al, 1999), and pollination (Bell et al, 2010). In Citra, differences in mean berry weight were cultivar dependent.…”

Postharvest quality of 'Emerald' blueberry cultivated in a subtropical region

“…One of the first available in the market, the Emerald cultivar is a southern highbush blueberry selected by University of Florida (Florida, USA) for its low cold requirement (temperatures below 7.2°C), early production, and large fruit size. When grown in Florida, its harvest extends from mid-April to mid-May (Kovaleski et al, 2015).…”

Summer Pruning Severity Affected Vegetative and Reproductive Traits in the Rabbiteye Blueberry (<i>Vaccinium virgatum</i> Ait.)

“…Summer pruning consists of cutting back shoots during the plant's active growth period from early summer through autumn to reduce the height of the bush and to stimulate branching and flower bud formation. However, most of the summer pruning studies on blueberries have been done in Chile and the United States (Bañados et al, 2009;Jorquera et al, 2014;Kovaleski et al, 2015a, b), where agroclimatic and management conditions are far different from those in the Japanese blueberry production areas. Müller (2011) found that summer pruning increased berry weight and diameter by reducing the total yield of the southern highbush blueberry in Stellenbosch, South Africa.…”