The Pacific northwestern United States is an important production region for northern highbush blueberry, with 25,300 acres in production in Oregon and Washington in 2016 (U.S. Department of Agriculture, 2017). Of the total blueberry production, 34% (≈80 million pounds) was sold to fresh markets, where fruit quality and shelf life are critical. In particular, firmness is an important aspect of fruit quality that is valued by growers, as it can extend the window of time in which fruit can be harvested, potentially allowing for machine harvest for fresh market and helping retain quality during shipping (Xu et al., 2015). Firmness is also important to packers and consumers as an indicator of quality (Ehlenfeldt and Martin, 2002; Moggia et al., 2017). However, a connection has been shown in rabbiteye (Vaccinium virgatum) and southern highbush (interspecific hybrids of Vaccinium sp.) blueberries between greater firmness and a greater incidence of fruit splitting (Marshall et al., 2008).
Berry splitting hastens the process of desiccation and necrosis, increases the risk of postharvest fruit rot, and most often requires fruit either to be diverted from fresh to processed markets or can render the fruit completely unmarketable. In rabbiteye blueberry, splitting can reduce marketable yield by up to 20% in some cultivars (Marshall et al., 2006, 2007). The most commonly grown cultivars in the Pacific northwestern United States are northern highbush blueberry, which have a low incidence of splitting in this region due to little rainfall during the summer months.
‘Legacy’, a hybrid of northern and southern highbush blueberry (Vorsa, 1998), has rapidly gained in popularity because of its high yield, desirable fruiting season, and excellent flavor. However, this cultivar has a greater tendency to split due its southern highbush heritage (Marshall et al., 2008), especially after a rainfall or overhead irrigation event. Although ‘Elliott’ does not typically split in this region, it is less firm than many other commonly grown cultivars (Yang et al., 2009) and has been found to split in some other production regions such as southern Chile (B.C. Strik, personal observation).
The biofilm (Parka; Cultiva, Las Vegas, NV) was developed and patented by Oregon State University for use in sweet cherry (Prunus avium) to reduce fruit splitting (referred to as “cracking” in cherries) when applied preharvest (Kaiser et al., 2014). The product is a wax-based, food-grade phospholipid biofilm applied to foliage and fruit intended to supplement the fruit’s surface cuticle and allow for increased elasticity and reduced cracking. During initial testing, it also advanced maturity (increased TSS and color) in some cases (Kaiser et al., 2014). The technology was further developed by the manufacturer for use in other crops, including blueberry. When the biofilm was tested in 2013 and 2015 on ‘Tifblue’ and ‘Brightwell’ rabbiteye blueberry in Georgia, both of which experience high rates of splitting when it rains during fruit ripening, it reportedly reduced fruit splitting (Cultiva, 2018); no other fruit quality traits, such as firmness or berry size, were measured. In 2016, additional trials were performed with biofilm on ‘Brightwell’, where applications increased marketable fruit yield but did not impact fruit quality or shelf life; no splitting occurred in any treatment due to low rainfall that year (E. Smith, personal communication).
The objectives of this study were to test the biofilm on two highbush blueberry cultivars commonly grown in the Pacific northwestern United States, Elliott and Legacy, to determine the impact on fruit quality. Timing and method of application were evaluated in two separate studies to determine best practices.
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