Response of Sunmuscat (Vitis vinifera L.) to Varying Cane Numbers When Managed on a Shaw Swing-Arm Trellis for Dried Grape Production

Abstract

Background and Aims. Dried grapes from Sunmuscat compose more than 50% of Australia’s production. Sunmuscat is late ripening which can lead to suboptimal drying conditions and darkening of the final product. The response of Sunmuscat to varying cane number per vine was studied with the aim to promote earlier ripening and optimise berry size and yield, without detrimental effects on dried product quality. Methods and Results. The study was conducted in a trellis dried, commercial vineyard with pruning level treatments of 6, 9, 12, and 15 canes per vine over 3 seasons. It included assessment of budburst and fruitfulness in spring; monitoring of grape ripening; measurement of yield, bunch number, and moisture content at harvest; and post-harvest assessment of dry berry mass and fruit colour. Traits strongly affected by season were fruitfulness, yield, berry development, juice composition (TSS, pH, and TA), and dried grape quality (colour, dry berry mass, and sugar per berry). Retention of high cane numbers produced a slight delay in ripening (i.e., a mean of 1.1°Brix), small berries, and an asymptotic yield response without an effect on dried fruit colour or moisture. A linear response for bunch loss between spring and harvest was found with increasing cane number. Conclusions. Retention of fewer canes increased berry size and promoted earlier ripening, but at the expense of yield. Significance of the Study. Bunch loss between spring and harvest was the major yield determinant being more important than budburst, shoot fruitfulness, or berries per bunch.