Influence of time of overhead shading on yield, fruit quality, and subsequent flowering of hardy kiwifruit, Actinidia arguta

Abstract

The effect of overhead shading on yield, fruit quality, and subsequent flowering was studied in 4‐year‐old Actinidia arguta ’Ananasnaya’ vines in Oregon, United States in 1998 and 1999. Experimental vines were shaded to 45% of full sun from 14 July to 14 August, 14 July to 10 September (harvest date), or 10 September to 16 November, 1998. Control vines were not shaded. Shading treatments were not repeated in 1999. Fruit fresh and dry weight development followed a similar growth pattern in all treatments. Shading had no effect on yield per vine or fruit fresh weight, length, diameter, and % soluble solids in 1998. Shading for 2 months before harvest significantly reduced fruit dry weight in 1998. Shading in 1998 did not affect percentage of budbreak or the number of buds, shoots, or fruitful shoots per vine in 1999. However, vines that were shaded had a significantly lower percentage of fruitful shoots than unshaded vines, especially vines shaded for 2 months before harvest in 1998. Vines shaded for 2 months before harvest had 48% fewer flowers and thus less yield than unshaded vines. Percent fruit set was not significantly affected by flower number per vine or by shading in the previous season. Unshaded vines produced an average of one more cluster per shoot distally (at node 12) than vines shaded for 1 or 2 months before harvest the previous year. There was no treatment effect on fruit fresh weight, dry weight, length, diameter, seed number, or % soluble solids of marketable fruit in 1999. Results show that overhead shading, as might occur with dense canopies, did not have a large impact on fruit quality or yield in the current season, but reduced yield the following season. Overhead shading for 2 months before fruit harvest, led to the greatest reduction in flower number the following season confirming that the period before fruit harvest is an important time for flower bud evocation in this species.