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G.R. Gingera, D.W. Davis, and J.V. Groth

Partial resistance effectively reduces common leafrust (Puccinia sorghi Schw.) epidemics in sweet corn (Zea mays L.). One measurable field component of partial resistance is delayed first pustule appearance (FPA), influenced by latent period and infection efficiency. This is the first report of delayed FPA against common rust in sweet corn. Our objectives were to determine 1) if differences in delayed FPA could be assessed in a field environment, 2) the relationship between delayed FPA and disease severity, and 3) the inheritance of delayed FPA. FPA was screened in a field environment during 1992 and 1993 using two susceptible U.S. station inbreds and 32 breeding lines selected for partial resistance to common rust. The range in mean delay in FPA on a genotype basis was 2.4 to 5.0 days in 1992 and 1.5 to 7.4 days in 1993. Although the rank correlation of genotypes between years was small (r = 0.27), several breeding lines had longer delayed FPA in both years while others produced shorter FPA delay in both years. Seven commercial sweet corn hybrids with a wide range of partial resistance did not differ (P ≤ 0.05) for delayed FPA. There was no correlation between disease severity and delayed FPA (r2 = 0.00 to 0.21) for breeding lines or commercial hybrids, indicating that selection for delayed FPA may be conducted independently of disease severity. In a generation mean analysis conducted in 1993 and 1994 for three high x low delayed FPA crosses, the genetic control of delayed FPA was primarily additive. Dominant genetic effects were found in two crosses and epistasis was not significant in any cross.

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Anna Marín, Elizabeth A. Baldwin, Jinhe Bai, David Wood, Christopher Ference, Xiuxiu Sun, Jeffrey K. Brecht, and Anne Plotto

evaluation of mango slices. Eight to 10 trained panelists performed descriptive sensory analysis of slices and rated the samples using a line scale with anchors at 0 (none) and 10 (high). Attributes were appearance (hue/color, cut-edge sharpness, flesh

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Roy E. McDonald, Lawrence A. Risse, and Charles R. Barmore

Chopped `Salinas' crisphead lettuce (Lactuca sativa L.) was packaged in four types of polymeric films and stored at 1 or 5C for 14 days. Discoloration and off-flavors developed in lettuce stored in the two films in which the naturally produced CO2 rose above 20%. In the two films (oriented low-density polyethylene) with O2 transmission rates higher than 3000 ml·m-2· day-1·atm-1 at 22C, CO2 remained below 20%, O2 was between ≈ 2% and 15%, and the lettuce was acceptable after 14 days of storage at either 1 or 5C. Appearance and flavor were affected more by temperature than by length of storage.

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Manuel Baez-Sañudo, Jorge Siller-Cepeda, Rosalba Contreras-Martinez, Laura Contreras-Angulo, Rosabel Velez, and Dolores Muy-Rangel

Mango `Keitt' is characterized by a poor external color development and a slightly high transpiration rate during ripening, which affect external quality. When fruit is ripening, the peel turns from a green to yellowish or dull green color, and the peel has no shine. We evaluated the effectiveness of three film coatings to reduce weight loss, improve appearance, and maintain quality during ripening of `Keitt' mango fruits. Four lots of fruits were obtained from a packinghouse in late September and transported to the laboratory. Each lot was sprayed at the commercial recommended rates with SemperFresh, Natural Shine, TFC 210, and FreshSeal coatings. Water sprayed fruits were used as a control. After applications, fruits were stored for 15 days at 22 °C and 85% RH to simulate marketing conditions. Quality parameters evaluated included weight loss (%), firmness, external and internal colors (hue, chroma, l), respiration rate (CO2 production), and chemical parameters such as pH, titratable acidity and °Brix. After 15 days, fruits coated with Natural Shine reduced 50% of the weight loss as compared to control fruits, while fruits coated with FreshSeal and SemperFresh reduced only 1.7% and 3.5%, respectively. Firmness declined from 155 N to 10 N during storage, being more evident on day 10, when fruits were table ripe. Fruits treated with SemperFresh were softer as compared with the other treatments. Titratable acidity decreased from 0.8% to 0.2% during storage and °Brix increased from 13 to 17–18 in all treatments. Fruit coated with Natural Shine had reduced weight and firmness loss. Additionally, fruits developed a better external color, with lower hue values, higher chromaticity and luminosity, which improve fruit appearance.

Open access

Qinglu Ying, Yun Kong, and Youbin Zheng

≈300 to 400 µmol·m −2 ·s −1 and a photoperiod of ≈16 h appears to be the optimal light environment for indoor production of microgreens based on crop yield and appearance quality ( Jones-Baumgardt et al., 2019 ; Ying et al., 2020 ). Also, plants grown

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S.M. Scheiber, David Sandrock, Erin Alvarez, and Meghan M. Brennan

appearance, inflorescence number, growth, and mortality of two ornamental grass species. Materials and methods On 1 July 2005, 68 (34 of each cultivar) 2.5-inch-diameter liners of ‘Gracillimus’ maiden grass and ‘Hamelin’ fountain grass (Emerald Coast Growers

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Juan C. Diaz-Perez, Ron Gitaitis, and Bikash Mandal

Tomato spotted wilt (TSW) is a serious constraint to tomato production in various regions of the world. The effect of TSW on tomato yield is largely influenced by time of infection. Early infection usually results in severe stunting of the seedling and even death of the plant. Plastic mulches have been found to affect both the incidence of TSW, and plant growth and yield of tomato. The objective of this study was to determine the effect of root zone temperature (RZT) as affected by plastic mulch on the timing of appearance of first TSW symptoms, vegetative top fresh weight (FW) and fruit FW in tomato. Under natural TSW infection as well as in artificially inoculated plants, vegetative top FW and fruit FW were both linearly related with number of days after transplanting (DAT) the plants were free from TSW symptoms. The plants grown on black mulch during the fall showed earlier appearance of TSW symptoms, and had significantly reduced vegetative growth and fruit yields. The mean RZT during the first 42 DAT—the time before the plants reached full canopy closure—significantly affected the timing of first appearance of TSW symptoms, tomato plant growth and fruit yield. Vegetative top FW (optimal RZT = 24.1 °C) and fruit FW (26.9 °C) fitted the quadratic relationships with the mean RZT during the first 42 DAT. In conclusion, utilization of plastic mulches that created conditions of RZT stress, particularly heat stress, resulted in reduced plant growth and yield and may predispose the plants to earlier expression of TSW symptoms compared to plants grown under RZTs more favorable to tomato plant growth.

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Sanliang Gu, Tera M. Bonney, and Leslie H. Fuchigami

Effect of media containing processed fiber (methane digested cow manure) as a substitute for peatmoss, micronutrient application, and medium mixing ratios of processed fiber with perlite were investigated in pansy cv. Maxima mix plants (Viola ×wittrockiana). Neither medium components nor micronutrients significantly influenced plant growth and appearance when plants were potted in medium containing either 60% processed fiber and 40% perlite, 100% processed fiber, or 60% peatmoss and 40% perlite and supplemented with either N–P–K or N–P–K with micronutrients. The plant size and biomass production of leaves increased with increasing proportion of perlite in the mixtures containing processed fiber while the number and biomass of flowers were not affected. Water content of leaves or flowers was not influenced by mixes of processed fiber and perlite. The processed fiber, either alone or mixed with other media components, was satisfactory for the production of pansy plants with or without micronutrient application.

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M.C. Dever, R.A. MacDonald, M.A. Cliff, and W.D. Lane

Cherry cultivars (Prunus avium L.) from the breeding program located at Agriculture and Agri-Food Canada, Research Centre, Summerland, B.C., were profiled for their sensory characteristics. Judges scored six visual attributes, five flavor/texture attributes, and the degree of liking on 10-cm anchored line scales. There were significant differences (P ≤ 0.001) in external firmness, size, and color intensity as well as differences in flesh firmness, juiciness, sweetness, sourness, and intensity of cherry flavor among the cultivars. Principal component analysis (PCA) showed the relationships among the internal sensory attributes, including a calculated sum of perceived sweetness and sourness, and the analytical values (pH, soluble solids concentration, sugar: acid ratio). Factor scores located individual cultivars on the PCA plot and provided a graphic illustration of their sensory characteristics.

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Xia Xu*, Zhongbo Ren, and Jiang Lu

Pierce's Disease (PD) is a major factor limiting grape production in the southeast United State. This disease is caused by a bacterium, Xylella fastidiosa Wells et al., which is transmitted to the xylem system of the grapevines primarily by glassy-winged sharpshooters (Homalodisca coagulata Say). Once it is in the xylem, the X. fastidiosa will use the xylem sap as a nutrient source to multiply, colonize, and eventually plug the xylem vessels and cause the PD in susceptible cultivars. On the other hand, symptoms of PD in tolerant cultivars do not appear until fruit maturation, and symptoms are rarely observed in PD resistant cultivars. In order to understand the correlation between X. fastidiosa and PD symptom development, a study was initialed to monitor X. fastidiosa in xylem of resistant, tolerant, and susceptible vines on a monthly basis. Presence of X. fastidiosa was detected directly from xylem sap of field-grown vines by medium culture and confirmed by polymerase chain reaction (PCR). Xylella fastidiosa was detectable throughout the growing season in PD susceptible cultivar `Chardonnay', PD tolerant Florida hybrid grape `Blanc du Bois', and muscadine cultivar `Carlos'. The bacteria were also appeared in the dormant vines with high density in cultivars `Chardonnay' and `Blanc du Bios'. Although X. fastidiosa was also found in dormant canes of `Carlos', the density decreased throughout the late fall and winter months, and they were hardly found before June. The results indicated that X. fastidiosa were carried over from previous season in cultivars `Chardonnay' and `Blanc du Bois', while in PD tolerant cultivar `Carlos', they were newly acquired from the sharpshooter feedings during the growing season.