2017 ASHS Annual Conference

Several commercially available plant growth regulators (PGRs) exist to help growers increase red color development on certain table grape cultivars. Research has shown that commercial PGRs can aid in table grape color development, but they tend to be expensive, toxic or have antagonistic effects if used in combination. This project will provide growers with additional information and choices regarding cheaper and safer PGRs to assist in improving table grape color and pack out rates. Crimson Seedless is a red, late season table grape variety developed by David Ramming and Ron Tarailo and was released to the industry in 1989. This variety is known as a late season variety and is harvested in mid-September through mid-November depending on weather and the season. Crimson Seedless has a high retail demand with its firm, crisp berry texture and good flavor. One of the main limiting factors for Crimson Seedless table grape production is proper color development. It has been reported that severe color deficiency and nonuniformity may result in half the crop being left unpicked in the field. Industry has reported that Ethephon showed inconsistent results regarding color enhancement but can lead to soft berries. Contrary to Ethephon, Abcisic acid (ABA) consistently enhanced berry color without affecting grape quality, but is a more expensive product. The organic bio-stimulant OR-151 is a non-toxic plant synergist based on plant oil extracts that has proven enhanced color development for red table grapes in other countries. The product is registered for use on grapes in California, but not thoroughly tested. A new study at Fresno State showed promising results for OR-151 when tested against Ethephon and ABA products. OR-151 was used in different combinations with Ethephon and ABA to determine if there are synergistic or antagonistic effects on Crimson Seedless color development. Results showed that OR-151 enhances the upregulation of certain anthocyanins using HPLC analysis. These anthocyanin enhancements showed that color development was enhanced in Crimson Seedless without affecting yield or cold storage potential. More uniform color development was also achieved with OR-151.