DECREASING SHOOT LENGTH IN 'FUJI SUPREMA' APPLE TREES WITH TRINEXAPAC-ETHYL IN SOUTHERN BRAZIL

The gibberellin biosynthesis inhibitor trinexapac-ethyl (Tri-E) can be an alternative to control the excessive growth of temperate fruit trees in Brazil. Tri-E was tested in ‘Fuji Suprema’ for its effects on shoot growth and fruit quality in two seasons in the city of Muitos Capões, RS state, Southern Brazil (28°27’16”S, 51°07’58”W, alt. 882 m). The trial was conducted in a randomized block design with four replications of the following treatments: Tri-E (Moddus_® 250 SC) at 200, 250, 400 and 500 mg/L, Prohexadione-calcium (Pro-Ca, Viviful_®) at 125 mg/L and Paclobutrazol (PBZ, Cultar_® 250 SC) at 125 mg/L, and an untreated control. Shoot length was reduced more than 50% by all doses of Tri-E and Pro-Ca in 2011/2012, whereas shoot length was reduced 36% by PBZ compared with control. However, in 2012/2013 shoot length was reduced approx. 20% for almost all doses of Tri-E and Pro-Ca in the first year. No differences in yield were observed between treatments and the control. A reduction in productivity of plants sprayed with Tri-E compared to the control was observed in 2012/2013. However, doses of 200, 250 and 400 mg/L Tri-E increased fruit set by more than 60% compared to the control. The results indicate that reduced shoot growth of trees treated with Tri-E can provide growers with an important tool to reduce pruning costs, however, the use must be considered because there was a decrease in productivity. Doses of 200 and 250 mg/L Tri-E reduced the vegetative growth of ‘Fuji Suprema’, resulting in firmer fruit and higher soluble solids, with no residual effect on post-harvest fruit quality.