The 2012 ASHS Annual Conference

Storage trials were conducted on 10 muscadine grape (Vitis rotundifolia) cultivars and selections.  Ripe berries were washed in 100 ppm chlorine and packed in 0.94 liter vented clamshells.  Clamshells were packed with and without UVASYS SO₂ emitting sheets and stored at 1 °C for 2 or 4 weeks.  Berries were removed from cold storage and berry firmness was measured after 1 and 4 days at room temperature.  Berries were then evaluated for rot or bleaching damage and stem scar integrity.  There was a large amount of variation in berry firmness initially, but differences declined after storage.  ‘Supreme' and ‘GA 1-1-48' were firmer than all other genotypes initially.  Day 14 firmness rankings largely reflected day 0 rankings, with ‘GA 1-1-48' and ‘Supreme' markedly firmer than all other genotypes.  Day 17 showed differences among genotypes, but only ‘Supreme' was dramatically firmer than all others.  At day 28 ‘GA 1-1-48' and ‘Supreme' were significantly more firm than all other genotypes, but by day 31 only ‘Supreme' was markedly more firm.  These results demonstrate that berry firmness varied widely over cultivars but differences largely disappeared after storage, especially after storage for four days at room temperature.  The one notable exception to this was the cultivar ‘Supreme' which maintained a firmer berry than the other cultivars.  The presence of wet scars significantly reduced berry firmness at all storage periods except for 17 days.  Interestingly berry firmness was reduced by the presence of a wet scar even during the initial measurements.  The reduction in firmness with wet scars may be more a result of mechanical relaxation of firmness rather than an increase of decay or loss of turgor pressure.  Several cultivars showed no improvement in berry firmness with the addition of SO₂ generators, and no cultivar showed improvement over every storage period tested.  Taken together these results suggest that the SO₂ generators only have a very modest effect on controlling berry rot and improving berry firmness.  No bleaching or other ill effects were observed with the SO₂ generators.  This study indicates that retention of berry firmness after storage is a relatively rare trait.  The cultivar ‘Supreme' was superior to all other selections and should be considered the standard to compare to when testing new selections for storage ability.   In addition, this cultivar is being used as a parent in the breeding program with the goal of improving storage ability.