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Shengrui Yao

Jujube or chinese date (Ziziphus jujuba) has fruit that is developed mainly from ovary plus some nectary disk tissue, and the fruit can appear smooth or bumpy on the surface. The objective of this study was to investigate the unique fruit development of ornamental ‘Teapot’ jujube. Unlike ‘Li’ and ‘Lang’, ‘Teapot’ jujube fruit had one to five protuberances on the shoulder of the fruit and few entirely lack protuberances. The stamens of ‘Teapot’ jujube flowers were fewer in number, misplaced in location, and deformed in shape—some stamens were anthers only while others were filament only. Deformed stamens of ‘Teapot’ jujube were always anchored in the nectary disk instead of at their normal location—near the edge of the nectary disk. After bloom, the residue of stamens, nectary disk, and ovary were all constituents of the developing fruit. The deformed stamens developed into the fleshy protuberances and equaled them in number. Fruit with only two protuberances predominated, which is how the ‘Teapot’ jujube acquired its name, but the ratio among protuberance categories varied between trees. With its unique and decorative fruit shape, and acceptable fruit quality, ‘Teapot’ jujube could be used as a backyard tree, both as an ornamental and for its fruit.

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Shengrui Yao

Jujube (Ziziphus jujuba Mill.) originated in China and grows well in a wide range of areas in the United States, especially the southwest. New Mexico State University’s Sustainable Agriculture Science Center has imported and collected over 50 jujube cultivars and conducted a series of jujube-related research projects. In this study, jujube phenology and pollen germination in New Mexico were investigated and two unique germplasm resources were reported. Jujubes leafed out 4–8 weeks later than most pome and stone fruits and bloomed 2–3 months later than apricots, peaches, and apples. It can avoid late frosts in most years in northern New Mexico and, thus, produce a crop more reliably than traditional fruit crops in the region. For the 48 cultivars tested for pollen germination, the germination rates ranged from 0% to 75% depending on the cultivar and year. ‘September Late’ had the highest pollen germination rate each year among all cultivars tested from 2012 to 2014, whereas ‘GA866’, ‘Maya’, and ‘Sherwood’ had the lowest. ‘Zaocuiwang’ was the first reported male-sterile jujube cultivar in the United States, and this character was consistent from year to year and, thus, it would be a valuable cultivar for jujube breeding. Cultivar Yu had pseudo-flowers which never bloomed or set fruit. It would be a useful germplasm as special landscape trees or for genomic study of jujube flowering-related genes.

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Shengrui Yao

Twelve peach (Prunus persica) cultivars, six apricot (Prunus armeniaca) cultivars, two japanese plum (Prunus salicina) cultivars, three european plum (Prunus domestica) cultivars, four sweet cherry (Prunus avium) cultivars, and three tart cherry (Prunus cerasus) cultivars were monitored for winter damage at New Mexico State University's Sustainable Agriculture Science Center in Alcalde, NM (main site), and the Agricultural Science Center in Los Lunas, NM (minor site), in 2011. Uncharacteristically low temperatures on 1 Jan. and 3 Feb. were recorded as −7.2 and −11.3 °F, respectively, at Alcalde, and 4.8 and −13.9 °F, respectively, at Los Lunas. On 10 Jan. at Alcalde, live peach flower bud percentage varied by cultivar, ranging from 11% for Blazingstar to 25% for PF-1, and 85% to 87% for Encore and China Pearl. Apricot flower buds were hardier, with 70% survival for ‘Perfection’, 97% for ‘Sunglo’, and 99% for ‘Harglow’ on 10 Jan. By 10 Feb., almost all peach flower primordia were discolored, with no cultivar showing more than 1% survival. Based on this information, the 10% kill of flower buds for most peach cultivars occurred at temperatures equal to or slightly higher than −7.2 °F, and 90% kill occurred between −7.2 and −11.3 °F. On 10 Feb., 0% to 15% of apricot flower buds on spurs or shoots of the middle and lower canopy had survived. For vigorous shoots in the upper canopy, apricot flower buds on 1-year-old shoots had a higher blooming rate than those on spurs of 2-year-old or older wood. Flower buds of japanese plum were also severely damaged with less than 0.2% survival for ‘Santa Rosa’ and 4.8% for ‘Methley’, but european plum were relatively unaffected with over 98% flower bud survival for ‘Castleton’ and ‘NY6’, and 87% for ‘Stanley’ after −11.3 °F at Alcalde. Cherry—especially tart cherry—survived better than peach, apricot, and japanese plum after all winter freezes in 2011.

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Shengrui Yao

This article summarizes jujube importation and culture history and current jujube cultivars in the United States. Described within are jujube taxonomy, biology, adaptation, fruit nutrition, pests and diseases, propagation, and research conducted in the United States. It also discusses the current issues with jujubes in the United States and possible solutions to them. Jujube adapted and grew well in the southern and southwestern United States, and it could become a valuable industry in the United States within 15 to 20 years.

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Shengrui Yao and Robert Heyduck

All jujube (Ziziphus jujuba) cultivars can be used as fruit trees and in landscaping, but there are four striking ornamental cultivars in our collection: Dragon, Mushroom, So, and Teapot. These cultivars are decorative and can be used for fruit, tree shape, or both as edible landscape plants. We evaluated these four ornamental jujube cultivars in central and northern New Mexico. All four cultivars grew and produced well but performed differently. ‘So’, imported from China in 1914, was a productive and contoured cultivar with medium-sized, sweet/tart fruit and bushy trees, with a decorative tree shape in winter. ‘Dragon’, a recent import from China, was the most dwarf cultivar tested, with small fruit and gnarled trees, and suitable for four-season ornamental use in landscapes. ‘Mushroom’, another recent import from China, had the most decorative fruit shape among the four cultivars tested, with vigorous and productive plants. ‘Teapot’, also a recent import from China, had irregular fruit shapes and vigorous and productive plants. All four cultivars were good edible landscape plants depending on customers’ preferences and space availability/limitation.

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Shengrui Yao and Carl J. Rosen

Five primocane raspberry (Rubus idaeus) cultivars were evaluated in a high tunnel and in the field at Grand Rapids, MN, which is located in U.S. Department of Agriculture (USDA) plant hardiness zone 3b. Bare root plants of five cultivars (Autumn Bliss, Autumn Britten, Caroline, Joan J, and Polana) were planted in the high tunnel and in the field, each with a randomized complete block design at 2 × 5.2-ft spacing on 8 May and 14 May 2008, respectively. A propane heater was used periodically for frost protection in the high tunnel. All five cultivars overwintered well and primocanes emerged with minor or no winter damage in the high tunnel in 2009. The high tunnel extended the growing season for ≈4 weeks in both years. Raspberry plants in the high tunnel produced higher yield than those in the field, total 154 lb (6655 lb/acre) from the high tunnel vs. 0.5 lb (43 lb/acre) from the field in 2008 and 379 lb (16,378 lb/acre) vs. 80 lb (3457 lb/acre) in 2009. ‘Caroline’ and ‘Polana’ had higher yields than ‘Autumn Bliss’; ‘Joan J’ and ‘Autumn Britten’ yields were intermediate and not different from ‘Caroline’, ‘Polana’, or ‘Autumn Bliss’ yields. In terms of harvest date, ‘Polana’ was the earliest among the five cultivars tested, followed by ‘Autumn Britten’, ‘Autumn Bliss’, and ‘Joan J’. ‘Caroline’ was the latest. Essential nutrients in leaves for all cultivars both in the field and in the high tunnel were within sufficient ranges. Spider mites (Tetranychidae) and raspberry sawflies (Monophanoides geniculatus) were the major insect problems. In conclusion, primocane-fruiting raspberries can be successfully grown in high tunnels and produce substantially higher yields than in field plantations in northern Minnesota or areas with similar climatic conditions.

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Shengrui Yao, Junxin Huang and Robert Heyduck

Fifty-six jujube cultivars were observed for their flowering habits and fruiting characteristics at Alcalde, New Mexico. Jujube cultivars were classified as morning blooming type or afternoon blooming type. Among the 56 cultivars observed, 24 belonged to the morning type and 32 belonged to the afternoon type. Eighteen out of the 56 cultivars had their blooming type reported for the first time. The sepal splitting for morning type occurred from sunrise to 1000hr, whereas it occurred between 1300 and 1600 hr for the afternoon type. Even though their opening time differed, pollen release happened during daytime for both—morning type released pollen in the afternoon and afternoon type released pollen in the late afternoon and the next morning. Rainy and cloudy weather delayed blooming for several hours. Each flower experienced the following stages during blooming: sepal splitting, sepal flat, petal standing, petal and anther separation, petal flat and anther standing, anther flat, and stigma browning; the time and duration of each stage varied with cultivar and blooming type. Flower size varied by cultivar and helps with cultivar identification. Cultivars Li, Li-2, Redland, Qiyuexian, Xiangzao, Teapot, and Daguazao were self-pollinating/self-fruitful in New Mexico. For open pollination, fruit set varied greatly by cultivar. ‘Abbeville’ had the best fruit set each year. Most cultivars had better fruit set from open pollination than self-pollination; however, self-fruitful cultivars Li, Li-2, and Redland had better fruit set with self-pollination than open pollination in some years. Open pollination increased fruit size for all cultivars. ‘Zhongning’, ‘Abbeville’, ‘Jinsi-2’, and ‘Globe’ had high seed percentage from open-pollinated fruit, whereas ‘Lang’, ‘Don Polenski’, ‘Junzao’, and ‘Xingguang’ did not produce fully developed seed in any years but some dark brown empty seedcoat sacs. Seed development was also affected by weather and pollination conditions. Fruit blooming type, pollen release, self-pollination, self-fruitfulness, self-fertility, and seed development are all critical information for jujube breeders, researchers, extension personnel, and growers.

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Shengrui Yao, Robert Heyduck and Steven Guldan

Jujube (Ziziphus jujuba Mill.), also called chinese date, cultivars have not been formally trialed in the United States after the 1950s. Currently, there are five to six commercially available jujube cultivars, with ‘Li’ as the dominant one. Both growers and consumers demand a wider range of cultivars to extend the maturation season and for different uses. We tested jujube cultivars at three locations in New Mexico [U.S. Department of Agriculture (USDA) hardiness zones 6a, 7a, and 8a] to assess their adaption and performance. These are early performance results for fresh eating cultivars. Jujubes were precocious; 50% to 95% of trees produced during their planting year, depending on cultivar and location. The average yield per tree for trees in their second to fourth year after planting were 409 g, 4795 g, and 5318 g at Alcalde; and 456 g, 3098 g, and 5926 g at Los Lunas, respectively. The yields varied by cultivar and location. ‘Kongfucui’ (‘KFC’) was the most productive cultivar at Alcalde and Los Lunas in both 2017 and 2018, followed by ‘Daguazao’, ‘Gaga’, ‘Honeyjar’, Maya’, ‘Redland’, and ‘Sugarcane’. ‘GA866’, ‘Alcalde #1’, ‘Zaocuiwang’, and ‘Sandia’ had the lowest yields among the 15 cultivars tested. ‘Alcalde #1’ was the earliest to mature with large fruit, suitable for marginal regions with short growing seasons, whereas ‘Sandia’ had the best fruit quality among all cultivars tested, suitable for commercial growers and home gardeners. ‘Maya’, ‘Gaga’, ‘Honeyjar’, and ‘Russian 2’ were very productive, early-midseason cultivars with small fruit but excellent fruit quality—a perfect fit for the home gardener market. ‘Li’, ‘Daguazao’, ‘Redland’, and ‘Shanxi Li’ were productive with large fruit. Cultivars grew faster and produced higher yields, larger fruit, and higher soluble solids at more southerly locations. This article discusses cultivars’ early performance up to the fourth year after planting. This is the first jujube cultivar trial report in the United States since the 1950s.

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Shengrui Yao, Ian A. Merwin and Michael G. Brown

Minirhizotrons were employed to study new root occurrence, turnover, and depth distribution of apple (Malus ×domestica Borkh.) rootstocks under four groundcover management systems (GMS): preemergence herbicide (Pre-H), postemergence herbicide (Post-H), mowed sod (Grass) and hardwood bark mulch (Mulch) that have been maintained since 1992 in an orchard near Ithaca, NY. Two root observation tubes were installed on both sides of one tree in three replicates for each GMS treatment. Root observations were taken at 2–3 week intervals during growing seasons of 2002 and 2003. Tree growth and yield data were collected annually since 1992. The Mulch and Post-H treatments had bigger trees and higher yields than other treatments; whereas the Grass treatment had the smallest trees and lowest yields. Higher number of new roots was observed in a light crop year (2002) than a heavy crop year (2003). Mulch trees had more shallow roots and Grass trees had fewer total roots than other treatments. Root diameter was positively correlated with overwintering root survival. The Pre-H GMS had higher root mortality during a hot and dry growing season (2002). GMS treatments affected root number and root depth distribution patterns. Hot and dry weather conditions and crop load reduced new root emergence, increased root mortality and reduced root median lifespan. GMS treatments together with environmental factors affected root growth, turnover and distribution.