Ten phenological and fruit quality traits were evaluated in seedlings from nine F1 low to medium chill full-sib peach (Prunus persica) families and their parents over 2 years at two locations (Fowler, CA, and College Station, TX) to estimate variance components, genotype by environment interaction (G×E), and phenotypic correlations using restricted maximum likelihood mixed and multivariate models. The removal of nectarine [P. persica var. nucipersica (fruit without fuzz)] and pantao (flat shape fruit) seedlings from the analysis decreased the heritability for the fruit size, blush, tip, and soluble solids concentration (SSC), indicating the importance of taking the effects of the major gene of nectarine/pantao into account when assessing the heritability of traits. A strong correlation coefficient (r = 0.92) found between ripe date (RD) and fruit development period (FDP) and between fruit weight (FW) and fruit diameter (FD), indicates that either measure is equally effective, although the negative correlation between bloom date (BD) and FDP (r = −0.46) implies earlier blooming during cool temperatures tends to extend FDP. FW, FD, blush, and SSC had moderately weak correlations with RD (r = 0.56, 0.53, −0.41, and 0.48) and FDP (r = 0.57, 0.56, −0.50, and 0.39, respectively), which could be explained either by the presence of a strong link between quantitative trait loci of these traits and the ripening date locus or the pleiotropic effect of ripening date on many quantitative fruit characters. The traits RD, FDP, and titratable acidity (TA) had the highest broad-sense heritability (H2) and lowest G×E. FW, tip, and shape showed the lowest H2, the highest of G×E variance to the genetic F (G×E variance/total genotypic variance), and high G×E, whereas the other traits showed moderate G×E. For the traits that had a higher G×E interaction, selection for or against these traits should be done at the production location. A moderate narrow-sense heritability (h2) was estimated for BD, blush, fruit tip, and shape. FW and FD showed low to moderate h2 while H2 was high, whereas RD, FDP, SSC, and TA showed low h2 and high H2 estimates, indicating important nonadditive effects for these traits.
Zena Rawandoozi, Timothy Hartmann, David Byrne, and Silvia Carpenedo
Renee T. Threlfall, John R. Clark, Aubrey N. Dunteman, and Margaret L. Worthington
Breeding and release of new fresh-market blackberries (Rubus subgenus Rubus Watson) is vital for competitive markets to address evolving changes and production challenges. Physical, composition, and sensory attributes of six University of Arkansas (UA) System Division of Agriculture blackberry cultivars (Caddo, Natchez, Osage, Ouachita, Ponca, and Prime-Ark® Traveler) were evaluated to identify marketable attributes. The consumer sensory study (n = 81) had two elements: a visual evaluation of displayed blackberries and an appearance, tasting, and firmness evaluation of the six cultivars using a 9-point verbal hedonic liking scale and a 5-point just about right (JAR) scale. Consumers preferred large blackberries when presented with individual berries of varying sizes and clamshells filled with equal weights of small or large blackberries. The largest of the six cultivars, Natchez and Caddo, were scored favorably for size and shape. Consumers also preferred clamshells with little to no red drupelet reversion, a postharvest disorder where black drupelets on the blackberry turn red during or after cold storage. Consumers did not detect differences in the appearance or firmness of the cultivars and rated the firmness of all cultivars favorably on the JAR scale. The physical and composition attributes of the six cultivars were within commercially acceptable ranges (soluble solids = 9% to 10%, pH = 3.1–3.8, titratable acidity = 0.6% to 1.4%, and berry weight = 6–10 g). ‘Ponca’, ‘Osage’, ‘Caddo’, and ‘Natchez’ were all rated highly for sweetness, sourness, overall flavor, and overall impression. ‘Ponca’ was rated high for sweetness, overall flavor, and overall impression and had 10.4% soluble solids, 0.82% titratable acidity, and a 12.8 soluble solids/titratable acidity ratio. The identification of these marketability attributes of fresh-market blackberries will provide information to advance breeding efforts for fruit with commercial potential.
Kim D. Bowman and Ute Albrecht
Modern citrus nursery production makes use of potted-tree propagation in greenhouses. Supplemental lighting is one method by which nursery tree growth and profitability may be significantly improved, but limited specific information is available. Five replicated experiments were conducted to determine the utility and effects of increasing daylength during the winter months by supplemental illumination from light-emitting diode (LED) or high-pressure sodium (HPS) lights in citrus nursery propagation. Studies used ‘Valencia’ sweet orange scion, the most common citrus cultivar grown in Florida, and the commercially important rootstocks sour orange, ‘Cleopatra’ mandarin, ‘US-812’, ‘US-897’, ‘US-942’, and ‘US-1516’. Comparisons used the three common types of citrus rootstock propagation: seed, stem cuttings, and micropropagation. Six responses were measured in the lighting experiments, including vegetative growth before budding, scion bud survival, and scion bud growth after budding. Supplemental HPS or LED light to extend daylength to 16 h in the citrus nursery during short-day winter months was observed to be effective in increasing unbudded rootstock liner growth and ‘Valencia’ scion growth on all rootstocks and propagation types. Generally, the positive effect on vegetative growth from an increased daylength was stronger with the HPS light than with LED light, while increasing daylength with LED light, but not HPS light, provided some increased bud growth initiation. Use of HPS or LED supplemental lighting to extend daylength offers significant growth advantage for the citrus nursery industry in winter.
Yulia A. Kuzovkina and Lorenzo Vietto
The International Poplar Commission, FAO UN, was appointed to serve as the International Cultivar Registration Authority for the genus Salix in 2013 (). Eight hundred and fifty-four cultivar epithets were included in the Checklist for Cultivars of Salix (Willow) to provide the baseline for the formal registration of new cultivars epithets (, ). Twenty-six new cultivar epithets have been registered since 2016 and included in the .
Wenwen Li, Liqiang Liu, Weiquan Zhou, Yanan Wang, Xiang Ding, Guoquan Fan, Shikui Zhang, and Kang Liao
The present study aims to reveal the karyotypic characteristics and genetic relationships of apricot (Prunus armeniaca L.) accessions from different ecological groups. Fourteen, 9, and 30 accessions from the Central Asian ecological group, North China ecological group, and Dzhungar-Ili ecological group, respectively, were analyzed according to the conventional pressing plate method. The results showed that all the apricot accessions from the different ecological groups were diploid (2n = 2x = 16). The total haploid length of the chromosome set of the selected accessions ranged from 8.11 to 12.75 μm, which was a small chromosome, and no satellite chromosomes were detected. All accessions had different numbers of median-centromere chromosomes or sub-median-centromere chromosomes. The karyotypes of the selected accessions were classified as 1A or 2A. Principal component analysis revealed that the long-arm/short-arm ratio (0.968) and the karyotype symmetry index (−0.979) were the most valuable parameters, and cluster analysis revealed that the accessions from the Central Asian ecological group and Dzhungar-Ili ecological group clustered together. In terms of karyotypic characteristics, the accessions from the Dzhungar-Ili ecological group and Central Asian ecological group were closely related.
Liming Chen, Heping Zhu, Leona Horst, Matthew Wallhead, Michael Reding, and Amy Fulcher
Laser-guided variable-rate intelligent spray technology is anticipated to reduce pesticide use in production of crops and safeguard the environment. However, the ability of this technology to effectively control insect pests and diseases of crops must be validated before it becomes part of integrated pest management programs. Abilities of three different intelligent sprayers were tested to control pest insects and plant diseases at one fruit farm and two ornamental nurseries in Ohio during three consecutive growing seasons. The same sprayers with disabled intelligent functions were used as conventional constant-rate applications for comparisons. Test crops were apple (Malus pumila), peach (Prunus persica), blueberry (Vaccinium sect. Cyanococcus), black raspberry (Rubus occidentalis), crabapple (Malus sp.), maple (Acer sp.), birch (Betula sp.), and dogwood (Cornus florida). There were five insects and six diseases total involved in the investigations in the fruit farm and two nurseries. The field tests showed the intelligent spray applications reduced pesticide and foliar fertilizer use by ≈30% to 65% on average during the 3-year experiments. At the same time, intelligent spray technology was similar or more effective than conventional spray technology when controlling insects and diseases on a variety of crops. These results demonstrated that intelligent spray technology was environmentally friendly and more effective for control of insect and disease pests in fruit farms and ornamental tree nurseries.
Marcela Miranda, Xiuxiu Sun, Christopher Ference, Anne Plotto, Jinhe Bai, David Wood, Odílio Benedito Garrido Assis, Marcos David Ferreira, and Elizabeth Baldwin
Coatings are generally applied to fruit as microemulsions, but nanoemulsions are still experimental. ‘Nova’ mandarins (Citrus reticulata) were coated with shellac or carnauba (Copernica cerifera) microemulsions or an experimental carnauba nanoemulsion; these were compared with an uncoated control during storage for 7 days at 20 °C. Coatings were also tested on ‘Unique’ tangors (C. reticulata × C. sinensis) stored for 14 days at 10 °C followed by a simulated marketing period of 7 days at 20 °C. Fruit quality evaluations included weight loss, gloss, soluble solids (SS), titratable acidity (TA), pH, SS/TA ratio, internal CO2, O2, fruit juice ethanol, and other aroma volatile content. Sensory visual shine and tangerine (C. reticulata) flavor rank tests after storage were conducted, followed by an off-flavor rating. The carnauba waxes resulted in less weight loss compared with the uncoated control and shellac coating during both experiments. There were no differences in gloss measurements of ‘Nova’ mandarins; however, shellac-coated fruit ranked highest for shine in a sensory test. For ‘Unique’ tangors, initially, shellac showed the highest gloss (shine) measurement; however, at the end of storage, the nanoemulsion exhibited the highest gloss, although it was not different from that of the microemulsion. Similarly, after storage, the nanoemulsion ranked highest for visual shine, although it was not different from that of the microemulsion. There were only minor differences in SS, TA, pH, and SS/TA among treatments. The internal CO2 gas concentration and juice ethanol content generally increased and internal O2 decreased during storage. The highest levels of CO2 and ethanol were found for the shellac treatment, as was the lowest O2, indicating anaerobic respiration. There were only minor differences among the other coating treatments; however, they were only sometimes different from those of the control, which generally had the highest O2, lowest CO2, and lowest ethanol. Shellac and the carnauba microemulsion also altered the volatile profile more than the control and the nanoemulsion did, especially for ‘Unique’ tangors. For ‘Unique’ tangors, the control and nanoemulsion ranked highest for tangerine flavor and had the least off-flavor at the end of storage. Among the coatings tested, the carnauba emulsions demonstrated less water loss, imparted more sustainable gloss, and caused less ethanol production than shellac, with the nanoemulsion exhibiting higher gloss measurements, less modifications of the atmosphere and volatile profile, and, consequently, better flavor compared with the microemulsion.
Sabin Khanal, Sarah R. Hind, and Mohammad Babadoost
Bacterial spot, caused by Xanthomonas spp., is one of the most important diseases of tomato in Illinois. Field surveys were conducted during 2017–19 to assess occurrence of bacterial spot in commercial tomato fields. Severity of foliage and fruit infection was recorded, and symptomatic samples were collected from three-to-five cultivars in three different farms in each of northern, central, and southern regions of Illinois. Severity of symptomatic foliage ranged from 0% to 91% (average 36.7%) and incidence of symptomatic fruit ranges from 0% to 30% (average 10.8%). During the surveys, 266 Xanthomonas isolates were collected and identified as Xanthomonas gardneri and X. perforans using Xanthomonas-specific hrp primers. Eighty-six percent of the isolates from the northern region were identified as X. gardneri, whereas 73% of the isolates from southern region were identified as X. perforans. Isolates from the central region were identified as X. perforans and X. gardneri 53% and 47% of the time, respectively. Multilocus sequence analysis using six housekeeping genes (fusA, gap-1, gltA, gyrB, lepA, and lacF) revealed the endemic population of X. gardneri and X. perforans. In addition to Xanthomonas, nine non-Xanthomonas bacterial genera were isolated from the samples, with most of the isolates classified as Microbacterium, Pantoea, and Pseudomonas.
Melissa Moher, Max Jones, and Youbin Zheng
The majority of commercial Cannabis sativa L. (cannabis) cultivators use a 12.0-hour uninterrupted dark period to induce flowering; however, scientific information to prove this is the optimal dark period for all genotypes is lacking. Knowing genotype-specific photoperiods may help to promote growth by providing the optimal photoperiod for photosynthesis. To determine whether the floral initiation of cannabis explants respond to varied photoperiods in vitro, explants were grown under one of six photoperiod treatments: 12.0, 13.2, 13.8, 14.4, 15.0, and 16.0 hours per day for 4 weeks. The percentage of flowering explants was highest under 12.0- and 13.2-hour treatments. There were no treatment effects on the fresh weight, final height, and growth index. Based on the results, it is recommended that an uninterrupted dark period of at least 10.8 hours (i.e., 13.2-hour photoperiod) be used to induce flowering for the ‘802’ genotype. In vitro flowering could provide a unique and high-throughput approach to study floral/seed development and secondary metabolism in cannabis under highly controlled conditions. Further research should determine if this response is the same on the whole-plant level.
Qinglu Ying, Chase Jones-Baumgardt, Youbin Zheng, and Gale Bozzo
Microgreens are specialty vegetables that contain human health-promoting phytochemicals. Typically, microgreens are cultivated in controlled environments under red and blue light-emitting diodes (LEDs). However, the impact of varying the proportions of these light qualities on the composition of diverse phytochemicals in indoor-grown microgreens is unclear. To address this problem, the levels of chlorophylls, carotenoids, ascorbates, phenolics, anthocyanins, and nitrate were examined in arugula (Eruca sativa L.), ‘Red Russian’ kale [Brassica napus L. subsp. napus var. pabularia (DC.) Alef.], ‘Mizuna’ mustard (Brassica juncea L.), and red cabbage (Brassica oleracea L. var. capitata f. rubra) microgreens following cultivation under LEDs supplying varying proportions of blue light (5% to 30%) and red light (70% to 95%). Varying the proportion of blue light did not affect the extractable levels of total chlorophyll, total carotenoids, or nitrate in all four microgreen species. Generally, the levels of reduced and total ascorbate were greatest in arugula, kale, and mustard microgreens at 20% blue light, and a minor decrease was apparent at 30% blue light. These metabolite profiles were not impacted by the blue light percentage in red cabbage. Kale and mustard accumulated more total phenolics at 30% blue light than all other blue light regimens; however, this phytochemical attribute was unaffected in arugula and red cabbage. The total anthocyanin concentration increased proportionally with the percentage of supplied blue light up to 30% in all microgreens, with the exception of mustard. Our research showed that 20% blue light supplied from LED arrays is ideal for achieving optimal levels of both reduced and total ascorbate in all microgreens except red cabbage, and that 30% blue light promotes the greatest accumulation of total anthocyanin in indoor-grown Brassicaceae microgreens, with the exception of mustard.