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Ying Li, Xiao-Li Hu, Robert N. Trigiano, Herbert Aldwinckle and Zong-Ming (Max) Cheng

Apple blotch caused by Alternaria alternata apple pathotype is a severe disease of apple (Malus ×domestica Borkh) occurring throughout the world, especially in eastern Asia. Phenotypic and genetic information about resistance/susceptibility of apple germplasm to this disease will be extremely valuable for selecting and developing new disease resistant cultivars. In this study, 110 apple cultivars obtained from the USDA apple germplasm in Geneva, NY, were evaluated for their resistance/susceptibility to apple blotch by field surveys, and inoculation of detached leaves with a suspension of germinated conidia of A. alternata apple pathotype. Disease incidence were different among the cultivars and categorized into resistant (R), moderately resistant (MR), or susceptible (S). Two molecular markers, S428, a random amplified polymorphic DNA (RAPD) marker associated with disease resistance, and a simple sequence repeat (SSR or microsatellite) marker CH05g07, linked to susceptibility were used to correlate the phenotypes expressed in field surveys and laboratory inoculations. The detection using either the S428 marker or the CH05g07 marker in 50 common breeding cultivars was consistent with R or S traits except for ‘Bisbee’ and ‘Priscilla’. These two cultivars were MR to apple blotch through phenotyping. However, SSR markers were detected, but RAPD markers were not and therefore were considered susceptible. Combined with the record of resistance to fire blight from Germplasm Resources Information Network (GRIN), ‘Dayton’, ‘Mildew Immune Seedling’, ‘Puregold’, and ‘Pumpkin Sweet’ were highly resistant to both diseases and considered as the best choices of parents for stacking resistance to multiple diseases in breeding program.

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Ting Zhou, Hao Jiang, Donglin Zhang, Junjun Fan, Long Zhang, Guibin Wang, Wangxiang Zhang and Fuliang Cao

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Shao-chang Qin, Juan-ling Li, Abdul Kareem and Yong Wang

Partridge tea is one of the famous local herbal teas of Hainan Island, China. In the present study, headspace solid-phase microextraction and gas chromatography-mass spectrometry were combined to determine and analyze the volatile components in the red and green leaves of partridge tea. Seventeen volatile components were identified in the red young leaves. The olefins, alkanes, and alcohols accounted for 71.24%, 1.1%, and 0.54%, among which the main components were caryophyllene (22.50%), humulene (18.73%), and α-guaiene (8.78%), respectively. Twenty volatile components were identified from red mature leaves, including 34.74% olefins, 6.14% esters, and 3.11% acids. Eighteen volatile components were identified from green young leaves, among which olefins (70.52%), alkanes (4.32%), and alcohol (0.89%) were the major components. Nineteen volatile components were identified from green mature leaves, among which the olefins, esters, and acids were the major components with the contents of 46.04%, 6.38%, and 1.37%, respectively. Results showed that the major volatile components of partridge tea were olefins, in which caryophyllene was the most abundant. The contents of volatile components between red leaves and green leaves had notable differences, which might be useful for germplasm identification of partridge tea.

Open access

Lisa W. Alexander, Anthony L. Witcher and Fulya Baysal-Gurel

Witchhazel (Hamamelis sp.) cultivars are now available in an array of forms and flower colors, including several native, pollinator-friendly cultivars. However, little is known about response of witchhazel cultivars to powdery mildew (Podosphaera biuncinata) or the growth and flowering characteristics of witchhazel cultivars in a nursery field production setting. To provide growth, flowering, and disease incidence data to nursery growers, a cultivar trial including 23 cultivars of witchhazel representing five species was planted Apr. 2016 in McMinnville, TN. Plant growth, flowering density, length of bloom, and foliar disease incidence were evaluated over three growing seasons between May 2016 and Oct. 2018. ‘Zuccariniana’ japanese witchhazel (H. japonica) and ‘Sunglow’ common witchhazel (H. virginiana) showed the greatest height increase during the trial, and ‘Sunglow’ also added the most width during the trial. Cultivars with negative height or width growth included Sweet Sunshine chinese witchhazel (H. mollis) and hybrid witchhazels (H. ×intermedia) Aphrodite, Twilight, and Barmstedt Gold. Ten of the 23 cultivars experienced winter injury in the form of stem necrosis. Root crown sprouts were observed for all cultivars at least once during the trial. ‘Wisely Supreme’ chinese witchhazel had the longest bloom period, followed by ‘Westerstede’ and ‘Twilight’ hybrid witchhazels, whereas ‘Quasimodo’ vernal witchhazel (H. vernalis) had the greatest density of flowers. The hybrid witchhazel cultivars Aphrodite, Nina, and Arnold Promise and the common witchhazel cultivars Green Thumb and Sunglow were resistant to powdery mildew under trial conditions in all 3 years. ‘Twilight’ and ‘Barmstedt Gold’ hybrid witchhazel, ‘Little Suzie’ common witchhazel, ‘Wisley Supreme’ chinese witchhazel, and ‘Shibamichi Red’ japanese witchhazel were moderately resistant to powdery mildew.

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Ze Li, Kai Shi, Fanhang Zhang, Lin Zhang, Hongxu Long, Yanling Zeng, Zhiming Liu, Genhua Niu and Xiaofeng Tan

As a result of its high photosynthetic efficiency, the tung tree (Vernicia fordii) is a fast-growing heliophile, yielding fruit within 3 years. In addition, tung oil extracted from the fruit seeds is an environmentally friendly paint used widely in China. However, mutual shading inside a tung tree canopy leads to a low yield of fruit because of weak or dead lower branches. In this project, a pot experiment was conducted to understand the growth, physiological, anatomical structure, and biochemical responses of tung trees under various shading levels. Tung tree seedlings were subjected to different light intensities—100% sunlight (no cover), L100; 75% sunlight (25% shading), L75; 50% sunlight (50% shading), L50; and 20% sunlight (80% shading), L20—from June to August. Results indicate that the L75 treatment reduced significantly the net photosynthetic rate (Pn), stomatal conductance (g S), transpiration rate (E), total aboveground and root dry weight (DW), maximum net photosynthetic rate (A max), and maximum rate of electron transport at saturating irradiance (Jmax) compared with the control, although plant height and leaf area (LA) were not reduced. Lower light intensities (L50 and L20) and longer duration of treatment led to greater reduction in growth, leaf thickness, and photosynthetic potential (A max and Jmax). Chlorophyll a (Chl a), chlorophyll b (Chl b), and total chlorophyll content were increased in the L50 and L20 treatments compared with L100 and L75. There was no significant reduction in the enzyme activities of ribulose-1,5-bisphosphate carboxylase (Rubisco) and phosphoenolpyruvate (PEPC) of the seedlings using the L75 treatment; however, lower light intensities (L50 and L20) and longer duration of shade treatment resulted in a significant reduction in enzyme activity. In summary, the results suggest that tung trees have greater photosynthetic activity under high light intensity. Shading, even at 20%, especially for the longer term, reduced photosynthetic efficiency and growth. To prevent growth reduction, tung trees should be grown under full sun with a daily light integral (DLI) of ≈46 mol·m‒2·d‒1, and mutual shading should be avoided by proper spacing and pruning.

Open access

Elena E. Lon Kan, Steven A. Sargent, Daniel J. Cantliffe, Adrian D. Berry and Nicole L. Shaw

Datil hot pepper (Capsicum chinense) has potential for increased production due to its unique, spicy flavor and aroma. However, few reports have been published related to postharvest handling characteristics. The purpose of this study was to determine the effect of harvest maturity on fruit quality under simulated commercial storage conditions. ‘Wanda’ datil pepper plants were grown hydroponically under protected culture. Fruit were harvested at yellow and orange maturity stages, placed in vented clamshell containers, and stored at 2, 7, or 10 °C for 21 days. Peppers harvested at yellow stage maintained greater quality than orange peppers during storage at all temperatures. Marketable fruit after 21 days for peppers harvested at the yellow stage was 94% (2 °C), 88% (7 °C), and 91% (10 °C); that for orange-stage peppers was 68%, 74%, and 82% for the same respective temperatures. No chilling injury (CI) symptoms were observed in these tests. Initial pepper moisture content was 90%, decreasing only slightly during 21 days of storage; weight loss ranged from 2% to 8%. Soluble solids content (SSC) was greater for peppers harvested at the orange stage (9.5%) than for those at yellow stage (7.8%). Neither harvest maturity nor storage temperature affected total titratable acidity (TTA; 0.13%) or pH (5.3). Respiration rate varied with temperature but not by harvest maturity and ranged from 12 to 25 mg·kg−1 per hour after 8 days of storage. Peppers harvested orange contained double the amount of total carotenoids as yellow fruit. Carotenoid content for yellow and orange peppers was 58 and 122 µg·g−1, respectively. Capsaicinoid content ranged from 1810 to 4440 µg·g−1 and was slightly greater for orange-harvested peppers. Datil peppers harvested at the yellow stage and stored in vented clamshell containers had better quality than peppers harvested at the orange stage after 21 days at 2 °C.

Open access

Shengrui Yao, Steve Guldan and Robert Heyduck

Late frost is the number one issue challenging fruit production in northern New Mexico. We had apricot (Prunus armeniaca) trees in an open field planting at Alcalde, NM, and not a single fruit was harvested from 2001 through 2014. Apricot trees in surrounding communities produce sporadic crops. In 2012, we planted apricots in two 16 × 40-ft high tunnels (9.5-ft high point). Trees were trained to a spindle system in one high tunnel and an upright fruiting offshoot (UFO) system in the other, and there were identical plantings in the open field for each high tunnel. Supplemental heating was provided starting at blooming time. There were five cultivars planted in each high tunnel at 4 × 8-ft spacing in a randomized complete block design with two replications (rows) and two trees per cultivar in each plot. In 2015, relatively high yields were obtained from all cultivars. The average yields for the spindle system were (lb/tree): ‘Puget Gold’ (29.0), ‘Harcot’ (24.1), ‘Golden Amber’ (19.6), ‘Chinese Apricot’ (18.6), and ‘Katy’ (16.7). Yields for the UFO system were (lb/tree): ‘Golden Amber’ (18.6), ‘Katy’ (14.9), ‘Puget Gold’ (11.3), ‘Chinese Apricot’ (10.2), and ‘Harcot’ (8.6). On average across all cultivars, the UFO system produced 60% of the yield of the spindle system in 2015. A heating device is necessary for high tunnel apricot fruit production in northern New Mexico because trees normally bloom in early to late March, depending on the year, while frosts can continue until mid-May. In years like 2017 and 2018 with temperatures below 10 °F in late February/early March, some of the expanded flower buds were killed before bloom. On those cold nights, one 100-lb tank of propane may or may not be enough for 1 night’s frost protection. Economically, it would not be feasible in those years. Only in years with a cool spring, late-blooming trees, and mild temperatures in April and May can high tunnel apricot production generate positive revenue with high, direct-market prices. High tunnel apricot production with heating devices is still risky and cannot guarantee a reliable crop in northern New Mexico or similar areas.

Open access

Carol A. Miles, Thomas S. Collins, Yao Mu and Travis Robert Alexander

Two studies were performed in Mount Vernon, WA, to identify bulb fennel (Foeniculum ×vulgare) cultivars and seeding practices best suited for the region. The first study evaluated 13 cultivars (Bronze, Finale, Florence, Genesi, Idillio, Orazio, Orion, Perfection, Preludio, Solaris, Tauro, Tenace, and Zefa Fino) over the course of 2 years; during the second year, the additional main factor of the seeding date was included. The second study evaluated three bulb fennel cultivars (Finale, Tauro, and Zefa Fino), four seeding dates (17 May, 31 May, 14 June, and 28 June 2018), and two planting methods (direct and transplant). Results of the two studies demonstrated that ‘Finale’, ‘Orazio’, ‘Preludio’, ‘Solaris’, and ‘Tenace’ had the greatest bulb production rate and yield and good bulb quality that met marketability standards. ‘Genesi’, ‘Orion’, and ‘Perfection’ had good bulb production during only 1 of the 2 years, whereas ‘Bronze’, ‘Florence’, ‘Idillio’, and ‘Zefa Fino’ had very low bulb productivity both years due to bolting. ‘Perfection’ and ‘Tauro’ exhibited internal cracking both years (incidence rates of 9.5% and 12.8%, respectively). The first harvest was 94 to 112 days after seeding during the first study. Direct seeded bulb fennel required 32 fewer days to harvest than transplanted bulb fennel during the second study. The average bulb circumference was 28.1 cm, with little variation between studies. Bulb tenderness for both studies was 617 g-force, on average, and the soluble solids concentration of bulbs in both studies was 4.9%. Ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry based on 38 tentatively identified compounds demonstrated no difference in the phenolic content of bulb fennel due to the cultivar. In conclusion, bulb fennel cultivars well-suited for production in northwest Washington were identified and direct seeding was demonstrated to be a better planting method than transplanting.

Open access

Suzanne P. Stone, George E. Boyhan and W. Carroll Johnson III

The southeastern United States produces 50% of U.S. conventional watermelon (Citrullus lanatus) but only 7% of U.S. organic watermelon. Weeds are a major threat to watermelon yield in the southeastern United States, and organic weed control is estimated to cost 20-times more than conventional herbicide programs. The objectives of this study were to determine the optimal weed control regime to reduce hand-weeding costs while maintaining yield and to compare the weed suppression of two watermelon types with differing growth habits in an organic system. In 2014 and 2015, watermelon plots were randomly assigned to the following treatments in a factorial arrangement: vine or compact growth habit; 1.0- or 0.5-m in-row spacing; and weekly weed control (kept weed-free by hoeing and hand-pulling weeds) for 0, 4, or 8 weeks after transplanting (WAT). At the time of the watermelon harvest, not weeding resulted in average total weed densities of 86.6 and 87.0 weeds/m2, and weeding for 4 WAT resulted in average total weed densities of 26.4 and 7.0 weeds/m2 in 2014 and 2015, respectively. Nonetheless, weeding for 4 WAT resulted in watermelon yields and fruit counts comparable to those of weeding for 8 WAT during both years. This partial-season weeding regime resulted in 67% and 63% weeding cost reductions for vine and compact plants, respectively, in 2014, and a 43% reduction for both growth habit types in 2015. In 2015, a separate experiment that evaluated weeding regimes that lasted 0, 1, 2, 3, 4, and 8 WAT found that yields resulting from weeding for 3 WAT were greater than those resulting from weeding for 2 WAT. However, the yields did not differ when weeding was performed for 4 WAT and 8 WAT.

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Ed Etxeberria, Pedro Gonzalez, Ariel Singerman and Timothy Ebert

Monitoring the health of Huanglongbing-affected citrus trees by following changes in leaf Candidatus Liberibacter asiaticus (CLas) titer has an inherent element of imprecision because CLas titer varies considerably within the tree canopy and with calendar seasons. In addition, the destructive sampling method used to determine CLas titer entails a different set of leaves per sampling period adding to the inconsistency and inexactitude of the results. To overcome these ambiguities and to reduce the numerical variability between samples, we developed an experimental method that analyzes portions of the same treated leaves for up to four sampling periods. By assaying subsamples of adjacent locations of the same leaf, random variability was significantly reduced, and comparative analysis can be carried out with greater precision.