Date of Graduation

12-2020

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor

Amanda McWhirt

Committee Member

Jackie Lee

Second Committee Member

Renee Threlfall

Keywords

berry yield, fruit quality, climate conditions, evaluation

Abstract

As blackberry production in the southeastern United States expands, the need for updated cultural practices, like alternative trellis systems that enhance blackberry fruit yield, fruit quality, and economic viability for fresh-market growers are needed. There are challenges to producing high-quality blackberry fruit with high yields in the Southeast due to intense heat, high rainfall, humidity, and heavy pest pressure. Southeastern growers are interested in the rotating cross-arm (RCA) trellis due to its potential to increase yield and fruit quality, however there is minimal research of its use in blackberry production in the Southeast. In 2019 and 2020, a trial was conducted at the University of Arkansas System Division of Agriculture (UA System) Fruit Research Station in Clarksville, AR to compare how the RCA trellis and a standard T-trellis impacted blackberry floricane cane morphology, floricane and primocane yield performance, pest damage to fruit and fruit quality of three blackberry cultivars (Osage, Ouachita, Prime-Ark® Traveler). The RCA had potential to increase floricane basal (proximal) cane length, and in some cases floricane node, and berry numbers of the cultivars evaluated compared to when they are grown on the T-trellis. Yield impacts varied by cultivar, but average berry weight was higher on the RCA for both floricane and primocane crops in both years. Floricane yield per plant was consistently higher for ‘Ouachita’ on the RCA compared to the T-trellis. Floricane crop yield per row meter (yield per m) was similar across trellis systems for ‘Ouachita’, but lower for ‘Prime-Ark® Traveler’ grown on the RCA compared to the T-trellis. Similar or lower yields per m between the two trellis systems are likely due to reduced plant canopy of plants per m row on the RCA due to disease that reduced main and lateral cane growth. Important trellising impacts on pest pressure and fruit quality were observed, including lower fruit infestation rates by spotted wing drosophila (SWD) (Drosophila suzukii) in both years, and lower rates of fruit weight loss, decay and red drupe reversion in some years on the RCA compared to the T-trellis.

Primocane yield of ‘Prime-Ark® Traveler’ varied for both years due to timing of summer soft-tipping, differences in flower bloom time and plant age, higher levels of hail damage, and disease. The RCA improved some post-harvest physical attributes (berry length, width, and weight) of primocane berries. The primocane training on the short-arm allowed on berries facing the south side of the RCA trellis, where the berries were highly exposed to direct sunlight on the south side of the trellis which in some years led to higher incidences of white drupe.

Overall, our results demonstrate that southeastern blackberry growers may benefit from using the RCA for increased yields per plant for ‘Ouachita’, reduced SWD infestation rates for all cultivars and improved floricane berry size, and weights. If blackberry canopy coverage on the RCA can be optimized, possibly through closer plant spacing, the benefits of this trellising system on yield and fruit quality could have the potential to improve blackberry production in the Southeast.

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