Unraveling the occasional occurrence of berry astringency in table grape cv. Scarlet Royal: a physiological and transcriptomic analysis

Ahmed Ismail; Tariq Pervaiz; Stacey Comstock; Sohrab Bodaghi; Alaaeldin Rezk; Georgios Vidalakis; Islam El-Sharkawy; David Obenland; Ashraf El-Kereamy

doi:10.3389/fpls.2023.1271251

Unraveling the occasional occurrence of berry astringency in table grape cv. Scarlet Royal: a physiological and transcriptomic analysis

Front Plant Sci. 2023 Oct 26:14:1271251. doi: 10.3389/fpls.2023.1271251. eCollection 2023.

Authors

Ahmed Ismail^{1

2}, Tariq Pervaiz¹, Stacey Comstock³, Sohrab Bodaghi³, Alaaeldin Rezk¹, Georgios Vidalakis³, Islam El-Sharkawy⁴, David Obenland⁵, Ashraf El-Kereamy¹

Affiliations

¹ Department of Botany and Plant Sciences, University of California Riverside, Riverside, Riverside, CA, United States.
² Department of Horticulture, Faculty of Agriculture, Damanhour University, Damanhour, Egypt.
³ Department of Microbiology & Plant Pathology, University of California Riverside, Riverside, Riverside, CA, United States.
⁴ Center for Viticulture and Small Fruit Research, College of Agriculture and Food Sciences, Florida A&M University, Tallahassee, FL, United States.
⁵ United States Department of Agriculture (USDA), Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, Parlier, CA, United States.

Abstract

Scarlet Royal, a mid-season ripening table grape, is one of the popular red grape varieties in California. However, its berries develop an undesirable astringent taste under certain conditions. Among the various factors contributing to the degradation of berry attributes, the levels and compositions of polyphenols play a fundamental role in defining berry quality and sensory characteristics. To comprehend the underlying mechanism of astringency development, Scarlet Royal berries with non-astringent attributes at the V7 vineyard were compared to astringent ones at the V9 vineyard. Biochemical analysis revealed that the divergence in berry astringency stemmed from alterations in its polyphenol composition, particularly tannins, during the late ripening stage at the V9 vineyard. Furthermore, transcriptomic profiling of berries positively associated nineteen flavonoid/proanthocyanidins (PAs) structural genes with the accumulation of PAs in V9 berries. The identification of these genes holds significance for table grape genetic improvement programs. At a practical level, the correlation between the taste panel and tannin content revealed a threshold level of tannins causing an astringent taste at approximately 400 mg/L. Additionally, berry astringency at the V9 vineyard was linked to a lower number of clusters and yield during the two study seasons, 2016 and 2017. Furthermore, petiole nutrient analysis at bloom showed differences in nutrient levels between the two vineyards, including higher levels of nitrogen and potassium in V9 vines compared to V7. It's worth noting that V9 berries at harvest displayed a lower level of total soluble solids and higher titratable acidity compared to V7 berries. In conclusion, our results indicate that the accumulation of tannins in berries during the ripening process results in a reduction in their red color intensity but significantly increases the astringency taste, thereby degrading the berry quality attributes. This study also highlights the association of high nitrogen nutrient levels and a lower crop load with berry astringency in table grapes, paving the way for further research in this area.

Keywords: berry quality; gene expression; grapevine nutrients; polyphenols; table grapes; tannins.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was funded by the California Table Grape Commission, https://www.grapesfromcalifornia.com.