Pre-harvest foliar application of Prohexadione-Ca and gibberellins modify canopy source-sink relations and improve quality and shelf-life of ‘Bing’ sweet cherry

Abstract

This research evaluated the potential of gibberellins (GA), and Prohexadione-Ca (PCa) to affect sweet cherry (Prunus avium) fruit size and quality. The results demonstrate the ability of ostensibly counter-acting plant growth regulators to significantly improve sweet cherry cv ‘Bing’ fruit size, fruit quality and postharvest characteristics compared to the current commercial application of GA3 alone. In 2008, we found that the combination of GA3 or GA4/7 (30 mg l−1) with PCa (150 mg l−1) applied to entire 3-year-old limbs 30 days after anthesis increased fruit size and improved fruit quality in ‘Bing’. In 2009, we investigated the effect of application timing in larger-scale field trials, comparing treatments made at 30 or 37 days after anthesis, on fruit quality, storability and sensory attributes after storage. Treatment with PCa + GA3 or PCa + GA4/7 delayed fruit maturity by about 7 days compared to the untreated control. Both the first and second applications of PCa + GA4/7 resulted in 35–40% fruit being ≥10 g, compared with only 20% in the control. PCa + GA3 treatment also showed greater potential for improving fruit storability by maintaining fruit firmness, sweetness, and consumer appeal than PCa + GA4/7. PCa alone or in combination with GAs inhibited current shoot growth and delayed fruit coloring development. After 30 days of 4°C storage, fewer than 5% fruit from untreated trees were rated as healthy and marketable, compared to 50 and 30% fruit from PCa + GA3 treatment applied at 30 or 37 days after anthesis, respectively. In conclusion, preharvest foliar application of PCa + GA3 at the onset of Stage II of fruit development shows potential to affect canopy source-sink relations and improved quality and shelf life of ‘Bing’ sweet cherries.