Postharvest Disease Development on Southern Highbush Blueberry Fruit in Relation to Berry Flesh Type and Harvest Method

Abstract

Mehra, L. K., MacLean, D. D., Savelle, A. T., and Scherm, H. 2013. Postharvest disease development on southern highbush blueberry fruit in relation to berry flesh type and harvest method. Plant Dis. 97:213-221.Postharvest decay, incited by various fungal pathogens, is a major concern in most blueberry production areas of the United States. Because the risk of infection is increased by fruit bruising, which in turn is increased by machine-harvesting, it has been difficult to harvest fruit from the early-maturing but soft-textured southern highbush blueberries (SHB) mechanically for the fresh market. This could change fundamentally with the recent development of SHB genotypes with crisp-textured ("crispy") berries, i.e., fruit with qualitatively firmer flesh and/or more resistant skin. Four replicate row sections of two or three SHB genotypes having crispy fruit and three with conventional fruit were either hand-or machine-harvested at a commercial blueberry farm in northern Florida in April 2009 and May 2010. Harvested fruit were sorted, packed, and placed in cold storage (2°C) for up to 3 weeks. Average counts of aerobic bacteria, total yeasts and molds, coliforms, and Escherichia coli on fruit samples before the cold storage period were below commercial tolerance levels in most cases. In both years, natural disease incidence after cold storage was lowest for hand-harvested crispy fruit and highest for machine-harvested conventional fruit. Interestingly, machine-harvested crispy fruit had the same or lower disease incidence as hand-harvested conventional fruit. Across all treatments, natural postharvest disease incidence was inversely related to fruit firmness, with firmness values >220 g/mm associated with low disease. In separate experiments, samples from the 0-day cold storage period were inoculated at the stem end with Altemaria alternata, Botrytis cinérea, or Colletotrichum acutatum, and disease incidence was assessed after 7 days in a cold room followed by 60 to 72 h at room temperature. In response to artificial inoculation, less disease developed on crispy berries. No significant effect of harvest method was observed, except for A. alternata inoculation in 2009, when hand-harvested fruit developed a lower level of disease than machine-harvested fruit. Taken together, this study suggests that mechanical harvesting of SHB cultivars with crisp-textured berries is feasible from a postharvest pathology perspective.

Applying New Technologies to Transform Blueberry Harvesting

“…Research has shown that blueberries harvested by OTR machines have significantly reduced shelf life [4,[6][7][8], and as much as 25% of fruit is lost to the ground, thus reducing the packable yield [8]. Also, blueberries harvested with conventional OTR harvesters exhibit excessive bruise damage and have lower fruit firmness (g/mm) than hand-harvested blueberries, and their quality deteriorates during >3 week postharvest cold storage required for marketing and for late-season distribution [4,7,9].…”

Correlation between sensory and instrumental measurements of standard and crisp‐texture southern highbush blueberries ( Vaccinium corymbosum L. interspecific hybrids)

“…Additional cultivars from other breeding programs that have been described as having crisp texture are ‘Dolores’ and ‘Hortblue Poppins’ . Berries with this crisp texture are of particular interest owing to their enhanced eating quality, prolonged postharvest life and potential value for mechanical harvesting for fresh marketed …”

“…Additionally, owing to rising labor costs and decreasing labor availability for hand harvesting of blueberries, the industry has been looking for ways to mechanically harvest fresh market berries . New machine harvesters have been designed and tested for use in blueberry, and research has been initiated to determine cultural practices and cultivars best suited for mechanical harvesting . Several bush and berry traits are thought to be desirable for mechanical harvesting methods, and berry firmness is top among them …”

“…6,7 Berries with this crisp texture are of particular interest owing to their enhanced eating quality, prolonged postharvest life and potential value for mechanical harvesting for fresh marketed. 8…”

Cell wall composition of the skin and flesh tissue of crisp and standard texture southern highbush blueberry genotypes

“…Many current selections in the UF blueberry breeding program are also considered to have a similar crisp phenotype, and other cultivars such as 'Reveille', 'Dolores', and 'Hortblue Poppins' have descriptions that indicate they would be classified as having crisp texture [1,3,4]. Berries with this crisp texture are of particular interest due to their enhanced eating quality, prolonged postharvest life, and potential value for mechanical harvesting for fresh marketed blueberries [5][6][7][8]. Understanding the physiological basis of this trait would potentially aid in selection and improvement through breeding efforts.…”