Grapevine trunk diseases are a major concern to the wine-and table-grape industries worldwide, limiting both vineyard longevity and productivity. Field surveys conducted throughout the grape-growing regions of Arkansas and Missouri revealed the presence of three economically important grapevine trunk diseases including, Botryosphaeria canker, Eutypa dieback and esca. Morphological studies along with multi-gene phylogenetical analyses confirmed the identification of 15 different fungal taxa associated with different vascular symptoms. These include Botryosphaeria dothidea, Diatrypella sp.

No abstract

A muscadine grape (Vitis rotundifolia) planting was established in 1996 at the Southwest Research and Extension Center in Hope, Ark., to provide information on the performance of muscadine grape cultivars in a region where cold hardiness is not a major limitation. This research evaluated harvest parameters, fruit and juice quality, and nutraceutical potential of selected muscadine cultivars grown in southwestern Arkansas. The cultivars evaluated were `Black Beauty', `Carlos', `Cowart', `Doreen', `Early Fry', `Fry', `Granny Val', `Ison', `Jumbo', `Late Fry', NC67A015-17, NC67A015-26, `Nesbitt', `Scarlett', `Southern Home', `Sterling', `Sugargate', `Summit', `Supreme', and `Tara'. Muscadine cultivars differed in productivity and fruit quality. In 2002 and 2003, juice was produced from `Carlos', `Granny Val', `Ison', `Nesbitt', `Southern Home', `Summit', and `Supreme' grapes. `Black Beauty' was also produced into juice in 2003. In 2002, `Nesbitt' grapes had the highest juice yield, 520 L·t–1 (124.6 gal/ton). `Ison' and `Supreme' juice had the highest soluble solids level. In 2003, `Granny Val' grapes had the highest juice yield, 551 L·t –1 (132.0 gal/ton). `Southern Home' juice had the highest soluble solids. The press materials of muscadine grapes were a potential source of high levels of nutraceutical compounds. Dried seeds had the highest total phenolic and oxygen radical absorbance capacity (ORAC) levels followed by the dried skins, the grapes, and then the juice. The skins of the black cultivars had the highest total anthocyanins level. `Supreme' seeds had the highest total phenolic and ORAC levels while `Ison' skins had the highest total anthocyanin levels. Based on yield, harvest, and juice quality, cultivars recommended to growers in southwestern Arkansas and other areas with a similar climate include `Black Beauty', `Carlos', `Fry', `Granny Val', `Nesbitt', `Southern Home', `Summit', and `Supreme'.

Grafting joins two distinct plant parts: a scion (shoot system) from a donor plant and a rootstock (root system) from a second plant to which the scion is attached. The practice of grafting chiefly enables clonal propagation but can also have many other benefits, such as reducing the juvenility period (increasing precocity) or size (dwarfing) in fruit trees (Fazio et al., 2014; Warschefsky et al., 2016;Webster, 1995).In grapevines (Vitis vinifera L.), widespread use of grafting began in the late 1800s, following the introduction of phylloxera (Daktulosphaira vitifoliae Fitch) to Europe from North America. While

19Grape growers use rootstocks to provide protection against pests and pathogens and to modulate 20 viticulture performance such as shoot growth. Our study examined two grapevine varieties 21 ('Chardonnay' and 'Cabernet Sauvignon') grafted to 15 different rootstocks and determined the 22 effect of rootstocks on eight traits important to viticulture. We assessed the vines across five 23 years and identified both year and variety as contributing strongly to trait variation. However, the 24 effect of rootstock was relatively consistent across years and varieties, explaining between 9% 25 and 10% of the variation in growth-related traits including yield, pruning weight, berry weight, 26 and Ravaz index (yield to pruning weight ratio). Increases in yield due to rootstock were 27 generally the result of increases in berry weight, likely due to increased water uptake by vines 28 grafted to a particular rootstock. We determined that it is possible to achieve an over 50% 29 increase in yield, pruning weight, and Ravaz index by choosing the optimal rootstock, indicating 30 that rootstock choice is crucial for grape growers looking to improve vine performance. 31 32 157 158

An evaluation of establishment techniques and rootstocks for ‘Chambourcin’ hybrid grape (Vitis sp.) was conducted 2009–12. Our objective was to evaluate four establishment methods and their interactions with grafted and ungrafted vines in terms of vine morphology and early fruit production under southwest Missouri conditions. The study was established in May 2009, as a factorial experiment comparing four establishment methods (open-trained without protection—two shoots, grow tube protected—two shoots, paperboard carton protected—two shoots, and fan-trained without protection—six shoots) across two vine types (own-rooted and grafted to ‘Couderc 3309’ hybrid grape rootstock). All vines in four of 12 field replications were destructively harvested near the conclusion of the first growing season, with leaf area and total vine dry matter determined. In years 3 and 4, yield, fruit composition, and vegetative growth were determined from the eight remaining replications. The fan training method increased leaf area and total vine dry matter compared with the other methods, but none of the establishment techniques affected fruit yield. Trunks that were tube protected had longer internodes, smaller diameter, and less dry matter, whereas both protection devices reduced glyphosate injury. Vine type (grafted and ungrafted) did not impact total leaf area or dry weight during the establishment year, but grafted vines had increased trunk and root shank dry weights compared with own-rooted vines. Grafted vines produced greater fruit yield in 2012. The fan training method required more labor to execute; although it was successful at increasing leaf area and root dry weight, it increased susceptibility to glyphosate injury and did not promote increased precocity or early fruit yield.

'Sunbelt' is a juice grape cultivar developed by the Univ. of Arkansas. This cultivar produces 'Concord'-type juice and is adapted to warm climatic conditions of the southern United States. Preliminary evaluation showed that 'Sunbelt' has potential to produce high-quality juice under the hot climatic conditions of the San Joaquin Valley. A study was conducted during the 1998 and 1999 growing seasons to further evaluate the adaptation of 'Sunbelt' to the San Joaquin Valley and determine the response of this cultivar to selected pruning methods. Vines were grown for two seasons without use of insecticides, fungicides, or herbicides. Vines were subjected to four pruning treatments: severe hand pruning (60-80 nodes retained/vine); moderate hand pruning (120-160 nodes retained/vine); machine pruning with hand follow-up (160-180 nodes retained/vine); and minimal pruning (200-400 nodes retained/vine). Vines were trained to a Geneva Double Curtain trellis system. Yield, components of yield, and juice quality were significantly impacted by pruning treatment. In both seasons, mechanized systems of pruning (machine and minimal) produced higher yield than hand pruning. Minimal pruning resulted in the highest yield (42 t·ha-1) in 1998, while yield from the machine-pruned vines was highest (29 t·ha-1) in 1999. Minimally pruned vines had the highest clusters/vine and lowest cluster weight among the treatments. The extremely high yields obtained for the minimal pruning treatments produced fruit that was less mature resulting in juice with lower soluble solids than the other treatments in 1998. However, in 1999 the juice from minimally pruned vines had the highest soluble solids. Sensory analysis of juice produced in 1999 showed that the juice from the machine-pruned treatment had the least color intensity. Sensory analysis showed that minimal and severe hand pruning were ranked higher for sweetness than machine and moderate hand pruning. In the second year of the study, the juice from the minimal-pruned and severe hand-pruned treatment were preferred over the moderate hand-pruned treatment or the machine-pruned treatment.

aged by crows. From these estimates, we calculated a 3 to 4% loss in production, about 40 pounds per acre, for those returning the survey. In estimating overall loss, average losses in the range of 1 to 5% and 6 to 10% were reported by 28% and 26% of the growers, respectively; 24% of the growers indicated losses in the range of 11 to 50%.