bluuebunny/crossref_metadata_2025 huggingface dataset:
Genome Sizes and Ploidy Levels in the Genus Kalmia
Authors: Gillooly Dominic A. , Ranney Thomas G.
Published: February 2019

Kalmia is a highly ornamental genus of shrubs native to North America and Cuba and grown as a valuable nursery crop throughout much of the temperate world. Although most species of Kalmia have previously been found to be diploid with 2n = 2x = 24, one species, Kalmia polifolia, has been found to be tetraploid. However, sampling within the genus has been limited, and information on the ploidy levels of specific cultivars is lacking. The objective of this study was to determine the relative genome sizes and ploidy levels of species, hybrids, and cultivars of Kalmia. Flow cytometry was used to determine the relative genome sizes of 67 accessions representing species, interspecific hybrids, cultivars, and chemically induced polyploids. Traditional cytology was used to calibrate genome sizes with ploidy levels. Results showed that relative genome sizes were conserved with 1Cx values ranging from 0.57 pg for Kalmia carolina to 0.70 pg for Kalmia latifolia. Most species of Kalmia were diploid including K. buxifolia (Leiophyllum buxifolium), K. carolina, K. cuneata, K. hirsuta, K. latifolia, and K. microphylla. Although plants of K. carolina (Kalmia angustifolia var. carolina) were uniformly diploid, the closely related, but more northerly distributed, K. angustifolia was primarily tetraploid, providing additional justification for treating these as separate species. An unusual triploid of K. angustifolia f. candida was also documented. Kalmia polifolia included both tetraploid and potentially pentaploid individuals, indicating a ploidy series within this species. Kalmia latifolia cultivars also included one triploid, two cytochimeras, and two chemically induced tetraploids. Overall, polyploidy was more prevalent in Kalmia than previously reported and varied both within and among species. This broader survey of relative genome sizes and ploidy levels in Kalmia provides valuable information for plant breeders and new insights into the systematics and cytogenetics of the genus.
Optimum Planting Configuration for High Population Plasticulture Grown Cabbage
Authors: Barrett Charles E. , Zotarelli Lincoln , Paranhos Lucas G. , Taylor Brian S. , Dittmar Peter , Fraisse Clyde W. , VanSickle John
Published: February 2019

Florida is a major fresh-market cabbage (Brassica oleracea L. var. capitata) producing state in the United States. The current cabbage production system relies on bare ground and subirrigation that requires a large volume of water to irrigate the crop. The bare ground system facilitates a maximum of 48,438 plant/ha, while there is a potential to increase plant population per area using plasticulture and drip irrigation. The objectives of this study were to determine the optimum cabbage plant population and plant arrangement that maximizes marketable yield per area for a high cabbage population plasticulture system. Cabbage was grown on 1.2-m-wide raised beds with black plastic mulch and drip irrigation. Plants were grown in either three or four rows with in-row plant spacings ranging from 15 to 35 cm and plant populations ranging from 41,518 to 129,167 plants/ha. Cabbage marketable yield increased as in-row spacing increased. Yields ranged from 19.7 to 69.7 Mg·ha−1. Marketable yield was not different between 3 and 4 rows for in-row spacings above 25 cm. The 15 and 20 cm in-row spacing produced significantly lower yields in the 4-row configuration as compared with the 3-row configuration in Fall and Winter 2011. Wider in-row spacings produced a greater percentage of heads of marketable size while reducing the percentage of small heads when compared with narrower in-row spacings. Mean head weight increased as in-row spacing increased and a 3- or 4-row configuration with an in-row spacing between 25 and 30 cm had consistently high yields in all three seasons compared with narrower in-row plant spacings. These results indicated that with a high population plasticulture system variable plant populations could be selected. In-row plant spacings between 30 and 35 cm may be beneficial for early plantings while a 25-cm spacing could be more productive for later plantings, especially when weather conditions are favorable.
Daily Light Integral Influences Steviol Glycoside Biosynthesis and Relative Abundance of Specific Glycosides in Stevia
Authors: Evans Jennifer M. , Vallejo Veronica A. , Beaudry Randolph M. , Warner Ryan M.
Published: February 2019

The biosynthesis of steviol glycosides is affected by both genetic and environmental factors. To evaluate the influence of total daily solar radiation or daily light integral (DLI) under long-day conditions on steviol glycoside concentration, we grew Stevia rebaudiana under ambient irradiance or varying levels of shading at different times of the year in both greenhouse and field environments, resulting in DLIs ranging from 3.55 to 20.31 mol·m−2·d−1 in the greenhouse and 10.32 to 39.7 mol·m−2·d−1 in the field. Total steviol glycoside concentration of selected leaves from greenhouse-grown plants increased as DLI increased up to ca. 10 mol·m−2·d−1, remaining constant with further increases in DLI, and was similar across the range of DLIs evaluated in the field. DLI influenced both the concentration and the relative proportions of specific steviol glycosides. Rebaudioside A concentration increased as DLI increased from 3.55 to 8.53 mol·m−2·d−1, remaining similar with further increases in DLI. Rebaudioside D and stevioside concentration of selected leaves from field-grown plants decreased by 22% and 13%, respectively, as DLI increased from 10.32 to 39.7 mol·m−2·d−1, while rebaudioside A and M concentrations remained similar across this DLI range. Collectively, these results indicate that the greatest influence of DLI on steviol glycoside concentration occurs under relatively low DLIs (<10 mol·m−2·d−1). However, higher DLIs can significantly affect the synthesis of minor glycosides of increasing commercial importance including rebaudioside D.
Tomatoes Grown with Light-emitting Diodes or High-pressure Sodium Supplemental Lights have Similar Fruit-quality Attributes
Authors: Dzakovich Michael P. , Gómez Celina , Mitchell Cary A.
Published: February 2019

Light-emitting diodes (LEDs) are an attractive alternative to high-pressure sodium (HPS) lamps for plant growth because of their energy-saving potential. However, the effects of supplementing broad-waveband solar light with narrow-waveband LED light on the sensory attributes of greenhouse-grown tomatoes (Solanum lycopersicum) are largely unknown. Three separate studies investigating the effect of supplemental light quantity and quality on physicochemical and organoleptic properties of greenhouse-grown tomato fruit were conducted over 4- or 5-month intervals during 2012 and 2013. Tomato cultivars Success, Komeett, and Rebelski were grown hydroponically within a high-wire trellising system in a glass-glazed greenhouse. Chromacity, Brix, titratable acidity, electrical conductivity (EC), and pH measurements of fruit extracts indicated plant response differences between lighting treatments. In sensory panels, tasters ranked tomatoes for color, acidity, and sweetness using an objective scale, whereas color, aroma, texture, sweetness, acidity, aftertaste, and overall approval were ranked using hedonic scales. By collecting both physicochemical as well as sensory data, this study was able to determine whether statistically significant physicochemical parameters of tomato fruit also reflected consumer perception of fruit quality. Sensory panels indicated that statistically significant physicochemical differences were not noticeable to tasters and that tasters engaged in blind testing could not discern between tomatoes from different supplemental lighting treatments or unsupplemented controls. Growers interested in reducing supplemental lighting energy consumption by using intracanopy LED (IC-LED) supplemental lighting need not be concerned that the quality of their tomato fruits will be negatively affected by narrow-band supplemental radiation at the intensities and wavelengths used in this study.
A Greenhouse-based Inoculation Protocol for Fungi Causing Crown Rust and Stem Rust Diseases of Kentucky Bluegrass Turf
Authors: Beirn Lisa A. , Meyer William A. , Clarke Bruce B. , Crouch Jo Anne
Published: February 2019

Rusts are destructive fungal diseases that can cause severe thinning and unattractive discoloration of kentucky bluegrass (KBG; Poa pratensis L.). Currently, turfgrass breeding programs rely on field evaluations to screen KBG germplasm for rust resistance; methods that are expensive, labor intensive, and require large turf areas. The availability of a greenhouse-based assay to perform prescreening of KBG germplasm for resistance to rust diseases before field trials would allow breeders to remove the poorest performing plants before field evaluations thus enhancing breeding efficiency. In this study, we set out to develop a reliable, low-cost greenhouse inoculation protocol for the two most common rust pathogens of KBG in temperate growing regions: Puccinia coronata and Puccinia graminis, the causal agents of crown and stem rust, respectively. Using a modified inoculation assay and custom-built plexi-glass chambers adapted from protocols used for cereal rust pathogens, urediniospores of crown and stem rust fungi developed on inoculated plants 10 to 14 days postinoculation. Real-time polymerase chain reaction (PCR) assays, disease symptomology, and morphology of urediniospores confirmed the presence and identity of both rust pathogens from inoculated host tissue. The inoculation protocols described here represent an effective method to accelerate screening of KBG germplasm for resistance to crown and stem rust diseases. Infection of KBG plants in the greenhouse will also allow breeders to maintain populations of crown and stem rust fungi throughout the year, providing a reliable and ongoing source of pathogen inoculum for experimentation and screening in the future.
Consumer Response to Novel Indoor Foliage Plant Attributes: Evidence from a Conjoint Experiment and Gaze Analysis
Authors: Rihn Alicia , Khachatryan Hayk , Campbell Benjamin , Hall Charles , Behe Bridget
Published: February 2019

A rating-based conjoint experiment combined with eye-tracking analysis was used to investigate the effect of plant attributes on consumer purchase likelihood for indoor foliage plants. The experiment assessed the effects of plant type (Dracaena marginata Lam., Guzmania lingulata, or Spathiphyllum wallisii Regel), volatile organic compound (VOC) removal capacity (high, low, or none specified), price ($10.98–14.98/plant), production method [certified organic, organic production (not certified), or conventional], and origin (in-state, domestic, or imported) on consumer preferences. An ordered logit model was used to analyze the data. Organic production methods, in-state origin, domestic origin, and high VOC removal increased participants’ purchase likelihood. Visually attending to the highest price point ($14.98) increased consumers’ purchase likelihood. Age, gender, child (<12 years), pet, relationship status, education, and ethnicity affected participants’ purchase likelihood for indoor foliage plants. Purchasing barriers for indoor foliage plants are also discussed. Results have implications for indoor foliage plant growers and retailers as they produce, promote, and sell their products.
Effect of Heat Treatment on Protein Content and the Quality of ‘Hujingmilu’ Peach [Prunus persica (L.) Batsch]
Authors: Zhou Hui-juan , Ye Zheng-wen , Su Ming-shen , Du Ji-hong , Li Xiong-wei
Published: February 2019

Heat treatment induces resistance to low temperature in horticultural crops. Changes in soluble protein and heat-stable protein (HSP) contents, the total soluble solids (TSS), titratable acidity (TA), reducing sugar, weight loss and firmness of honey peach (cv. Hujingmilu) during heat treatment and refrigerated storage were investigated. Low-temperature storage alone led to decreasing of TA and reducing sugar and caused severe fresh mealiness. The hot-air treatment before low temperature combined with the use of a plastic bag (thickness of 0.03 mm) could counteract this effect. Heat treatment before refrigerated storage increased both soluble protein and HSP contents, and the ratio of heat-stable to soluble protein. The most favorable effect was obtained with 46 °C for 30 minutes. In addition, heat treatment before storage retarded the increase in fruit firmness, maintained the highest contents of the TSS and reducing sugar and inhibited the decline of TA during refrigerated storage. Treatment for 30 minutes at 46 °C before low-temperature storage in combination with a 0.03-mm plastic bag might be a useful technique to alleviate chilling injury (CI) and maintain honey peach fruit quality during cold storage.
Effects of Root Pruning on Germinated Pecan Seedlings
Authors: Zhang Rui , Peng Fang-Ren , Yan Pan , Cao Fan , Liu Zhuang-Zhuang , Le Dong-Liang , Tan Peng-Peng
Published: February 2019

Root systems of pecan trees are usually dominated by a single taproot with few lateral roots, which are commonly thought to inhibit successful transplanting. This study aimed to evaluate early growth and root/shoot development of pecan seedlings in response to taproot pruning. Taproots of ‘Shaoxing’ seedling pecan trees were mildly (1/3 of the total length of the radicle removed) and severely (2/3 of the total length of the radicle removed) pruned at different seedling development stages shortly after germination. At the end of the first growing season, top growth was measured and then trees were uprooted so that root system regrowth could be evaluated. The results showed that root pruning had no impact on increases in stem height or stem diameter. However, pruning the taproot could stimulate primary growth in taproot branches. Root weight and the number of taproot branches per tree increased with decreasing taproot length. This study indicated that severe root pruning when three to five leaves had emerged resulted in root systems with more taproot branches and the greatest root dry weight after one growth season, which may increase survival and reduce transplanting shock.
Irrigating Based on Daily Water Use Reduces Nursery Runoff Volume and Nutrient Load Without Reducing Growth of Four Conifers
Authors: Pershey Nicholas A. , Cregg Bert M. , Andresen Jeffrey A. , Fernandez R. Thomas
Published: February 2019

The objectives of this study were to quantify irrigation volume, runoff volume and nutrient content, and plant growth of container-grown conifers when irrigated based on plant daily water use (DWU) vs. a standard irrigation rate. Four conifer taxa were grown in 10.2-L (no. 3) containers subjected to four irrigation treatments from 23 June to 16 Oct. 2009 and 6 June to 31 Oct. 2010. The taxa were: 1) Chamaecyparis obtusa Sieb. & Zucc. ‘Filicoides’, 2) Chamaecyparis pisifera (Sieb. & Zucc.) Endl. ‘Sungold’, 3) Thuja occidentalis L. ‘Holmstrup’, and 4) Thuja plicata D. Donn ‘Zebrina’. The four irrigation treatments were: 1) control application of 19 mm·d−1, 2) irrigation applied to replace 100% DWU (100 DWU) per day, 3) applications alternating 100% with 75% DWU in a 2-day cycle (100–75 DWU), and 4) a 3-day application cycle replacing 100% DWU the first day and 75% DWU on the second and third days (100–75–75 DWU). Irrigation treatments did not affect plant growth index {GI= [(H + WNS + WEW)/3]} in 2009. In 2010, GI of C. obtusa ‘Filicoides’ was greater for 100 DWU than the control plants. Seasonal total water applied for 100, 100–75, and 100–75–75 DWU was 22%, 32%, and 56% less, respectively, than the control amount of 117 L per container in 2009 (114 days) and 24%, 18%, and 24% less than the control amount of 165 L per container in 2010 (147 days). Scheduling irrigation based on DWU reduced runoff volumes and (nitrate-nitrogen) NO3−-N and (phosphate-phosphorous) PO43−-P load compared with the control. Irrigating based on DWU reduced water application and runoff volumes and NO3−-N and PO43−-P load while producing plants of equal or greater size than control plants.
Relative Salt Tolerance of Seven Texas Superstar® Perennials
Authors: Sun Youping , Niu Genhua , Perez Christina
Published: February 2019

Salt tolerance of seven Texas Superstar® perennials [Malvaviscus arboreus var. drummondii (Turk’s cap), Phlox paniculata ‘John Fanick’ (‘John Fanick’ phlox), Phlox paniculata ‘Texas Pink’ (‘Texas Pink’ phlox), Ruellia brittoniana ‘Katie Blue’ (‘Katie Blue’ ruellia), Salvia farinacea ‘Henry Duelberg’ (‘Henry Duelberg’ salvia), Salvia leucantha (mexican bush sage), and Verbena ×hybrida ‘Blue Princess’ (‘Blue Princess’ verbena)] was evaluated in a greenhouse experiment. Plants were irrigated with a nutrient solution at electrical conductivity (EC) of 1.1 dS·m−1 (control) or a salt solution at EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) for 8 weeks. ‘John Fanick’ and ‘Texas Pink’ phlox plants in EC 5 had severe salt foliage damage, while those in EC 10 were died. Mexican bush sage in EC 10 had severe salt foliage damage. Turk’s cap, ‘Katie Blue’ ruellia, ‘Henry Duelberg’ salvia, and ‘Blue Princess’ verbena had minor foliar damage regardless of treatment. EC 5 reduced the shoot dry weight (DW) by 45% in ‘Texas Pink’ phlox and 11% to 18% in ‘Katie Blue’ ruellia, ‘Henry Duelberg’ salvia, and mexican bush sage, but did not impact the shoot DW of Turk’s cap and ‘John Fanick’ phlox. EC 10 further decreased the shoot DW of ‘Katie Blue’ ruellia, ‘Henry Duelberg’ salvia, and mexican bush sage plants by 32%, 29%, and 56%, respectively. EC 5 decreased leaf net photosynthesis (Pn) of ‘Texas Pink’ phlox and mexican bush sage, while EC 10 reduced Pn of all species except ‘Henry Duelberg’ salvia and ‘Blue Princess’ verbena. ‘Katie Blue’ ruellia and ‘Blue Princess’ verbena had relatively lower leaf Na concentration and ‘John Fanick’ phlox, ‘Texas Pink’phlox, and mexican bush sage had higher leaf Cl concentrations. In summary, Turk’s cap, ‘Katie Blue’ ruellia, ‘Henry Duelberg’ salvia, and ‘Blue Princess’ verbena were the most tolerant perennials, and ‘John Fanick’ phlox, ‘Texas Pink’ phlox, and mexican bush sage were the least tolerant to salinity.
Nitrogen and Potassium Requirements for Field-grown Areca and Mexican Fan Palms
Authors: Broschat Timothy K.
Published: February 2019

Potassium (K) deficiency is a widespread problem in palms growing in sandy or calcareous soils in southeastern United States. Its symptoms are highly conspicuous, reduce palm aesthetic appeal, are difficult to correct, and can be exacerbated by nitrogen (N) fertilization. The objective of this study was to determine the optimum fertilization rates and ratio for N and K in areca palm [Dypsis lutescens (H. Wendl.) Beentje & J. Dransf. and Mexican fan palm (Washingtonia robusta H. Wendl.) growing in a calcareous sandy fill soil. Both species had their highest quality when fertilized with 12.2 g·m−2 N and 12.2 g·m−2 K from controlled-release (2–3 month release) sources every 3 months. Actual N and K application rates were better predictors of palm quality than N:K ratio at the highest fertilization rates that would be recommended for field nursery production. However, at lower application rates more typical of those used for landscape palm maintenance, palm quality improved as the N:K application ratio was decreased.
Compilation of the Checklist for Cultivars of Salix L. (Willow)
Authors: Kuzovkina Yulia A.
Published: February 2019

The long history of Salix L. cultivation has resulted in selections of cultivars with superior technical and ornamental characteristics. Numerous cultivars have been developed and named over the centuries, but until now, no comprehensive compilation of these records has ever been made. With the expanding domestication of the genus Salix and the active selection of new cultivars, it is increasingly important that we have clear and standardized records documenting the cultivars. In 2013, the International Poplar Commission of the Food and Agriculture Organization (IPC FAO) was appointed as the International Cultivar Registration Authority (ICRA) for willows. The Checklist for Cultivars of Salix was compiled as the first step toward the promotion of a standardized registration process and the establishment of a Cultivar Register for Salix. Eight hundred and fifty four cultivar epithets with accompanying information have been included in the Checklist. The largest group of cultivars—more than 200—is represented by basket selections. This is followed by selections for ornamental plantings and biofuel production. The Checklist aims to promote the uniformity and accuracy of cultivar names of Salix, and provides a baseline for new registrations to ensure that each newly developed cultivar receives a unique, authoritative botanical name.
The Carbohydrate Yield of Sweetpotato (Ipomoea batatas) Grown from Slips and Root Pieces in North Carolina
Authors: George Nicholas A. , Pecota Kenneth V. , Yencho G. Craig
Published: February 2019

Sweetpotato (Ipomoea batatas) is one of the world’s most important and widely grown starch crops. It is usually produced for direct human consumption but can be readily converted to simple sugars that then have industrial end uses. The objective of this study was to compare the carbohydrate yield of the conventional sweetpotato cultivar, Beauregard, with new clones selected specifically for higher carbohydrate production. Ten sweetpotato clones were grown from both slips and root pieces at five locations, over 2 years, in North Carolina. A sweetpotato clone selected for high carbohydrate production, and planted as slips, yielded on average 4150 kg·ha−1 of carbohydrates, 10% to 15% higher than Beauregard. The chemical composition of roots was unaffected by planting method, but slips usually outyielded the same clone grown from root pieces. Carbohydrate yield was significantly impacted by genotype × environment effects in both slips and root pieces. We conclude that further work will be needed to develop sweetpotato clones with both high carbohydrate content and high yield potential, and that are also adapted to planting from root pieces. Any breeding and development work will need to take into account genotype × environment effects.
Phylogenetic Relationships in the Genus Rosa Revisited Based on rpl16, trnL-F, and atpB-rbcL Sequences
Authors: Liu Chengyuan , Wang Guoliang , Wang Hui , Xia Tao , Zhang Shouzhou , Wang Qigang , Fang Yanming
Published: February 2019

Three chloroplast DNA (cpDNA) sequences [the rpl16 intron, the trnL-F, and atpB-rbcL intergenic spacer (IGS)] were employed to study phylogenetic relationships in the genus Rosa. Phylogenetic analyses using these three concatenated sequences were performed using maximum parsimony (MP) and Bayesian inference (BI) methods. Both analyses results suggest that the molecular phylogeny conforms closely to the conventional classification of botanical sections. Morphological similarities between R. sects. Synstylae and Chinenses, and R. sects. Rosa and Carolinae are corroborated on the molecular level in our analyses. Four taxa from R. sect. Pimpinellifoliae are further divided into two small clades, which reflect the morphological characters for these species on a molecular level. Whereas three accessions of R. foetida from R. sect. Pimpinellifoliae form a separate clade. R. ×fortuniana forms a clade with R. laevigata based on its maternal inheritance of cpDNA. R. ×cooperii is hypothesized to be a hybrid with seed parent from R. sects. Synstylae and Chinenses. And R. roxburghii should be classified as a section within the R. subgen. Rosa, rather than being treated as its own subgenus, based on molecular analyses.
Characterization of Spinach Germplasm for Resistance Against Two Races of Verticillium dahliae
Authors: Mou Beiquan , Klosterman Steven J. , Anchieta Amy , Wood Elisabeth , Subbarao Krishna V.
Published: February 2019

Historically, wilt disease caused by Verticillium dahliae has not presented a problem in California spinach production because the crop is harvested well before the symptoms develop after the stem elongation (bolting) stage. However, infested spinach seeds introduce or increase inoculum in the soil for rotational crops such as lettuce. This investigation was designed to identify verticillium wilt-resistant accessions in the U.S. Department of Agriculture (USDA) spinach germplasm collection against races 1 and 2 of V. dahliae, and to examine seed transmission of the pathogen in different spinach genotypes. In a seed health assay of 392 accessions, 21(5.4%) were positive for V. dahliae, and 153 (39%) were positive for Verticillium isaacii. A total of 268 accessions plus nine commercial cultivars were then screened against one race 1 and two race 2 isolates from spinach in replicated greenhouse experiments. Disease incidence, severity, and seed transmission through plating on NP-10 medium and real-time quantitative polymerase chain reaction (qPCR) were assessed. There was wide variation among accessions in their response to V. dahliae with disease incidence ranging from 0% to 100%. The two race 2 isolates differed in their virulence against spinach genotypes. Resistant accessions were identified against both races 1 and 2. Recovery of V. dahliae from seeds plated on NP-10 medium and qPCR results were highly correlated (P = 0.00014). Some accessions identified as resistant based on disease incidence showed little seed transmission of the pathogen. Even though lower wilt incidence and severity generally corresponded with lower seed transmission rates, there were exceptions (r = 0.52). Variation among plants within accessions was also observed. Nevertheless, the sources of resistance identified in this study are useful for spinach cultivar improvement.
Yield, Tree Size, and Fruit Quality of Mature ‘Owari’ and ‘Brown Select’ Satsuma on Poncirus trifoliata ‘Rubidoux’ and ‘Flying Dragon’ Rootstocks in North Florida
Authors: Andersen Peter C. , Brodbeck Brent V.
Published: February 2019

There is increasing interest in the culture of satsuma citrus in the states bordering the northern Gulf of Mexico. Yield, tree size, and fruit quality of mature ‘Owari’ and ‘Brown Select’ satsuma (Citrus unshiu Marcovitch) on Poncirus trifoliata (L.) Raf. (‘Rubidoux’ and ‘Flying Dragon’) were evaluated in north Florida. Canopy area and volume, yield, and fruit quality data were analyzed as a 2 × 2 factorial design with scion and rootstock as the main effects. There were no scion × rootstock interactions. Overall average yield per tree was 16, 88, 91, 143, and 101 kg in 2010, 2011, 2012, 2013, and 2014, respectively. Yield was influenced by scion (higher for ‘Brown Select’) in three of five years, and by rootstock every year (higher for ‘Rubidoux’). Yield per tree was ≈2-fold greater for trees on ‘Rubidoux’ compared with ‘Flying Dragon’; the highest yield was recorded for ‘Brown Select’ on ‘Rubidoux’. Yield per m2 canopy area was often similar since canopy area was often ≈2-fold greater for trees on ‘Rubidoux’. For three of the five years, fruit weight was greater for ‘Brown Select’ (average = 157 g) than ‘Owari’ (average = 146 g), with no rootstock effect. Soluble solids of juice averaged 10.0 °Brix and were higher for trees on ‘Flying Dragon’ than on ‘Rubidoux’ in three of five years. Juice pH averaged 3.67 and was unaffected by scion or rootstock. Trees were not subjected to freeze protection and were not damaged by minimum temperatures as low as −9.4 °C, except for 2014/15. A rating of defoliation after a freeze on 19 Nov. 2014 (−5.6 °C) indicated that cold hardiness varied by scion (greater for ‘Brown Select’) and rootstock (greater for ‘Rubidoux’). Differences in cold hardiness did not persist when assessed later in the winter. Successful satsumas production can be achieved in north Florida in the absence of a severe freeze event.
Grafting Affects Growth, Yield, Nutrient Uptake, and Partitioning Under Cadmium Stress in Tomato
Authors: Kumar Pradeep , Edelstein Menahem , Cardarelli Mariateresa , Ferri Emanuela , Colla Giuseppe
Published: February 2019

A greenhouse experiment was conducted to determine the influence of long-term cadmium (Cd) exposure (0, 25, or 50 µm of Cd) on crop productivity, fruit quality, leaf chlorophyll content, fluorescence, and mineral composition in plants of tomato (Solanum lycopersicum L. cv. Ikram), either nongrafted, self-grafted, or grafted onto rootstocks of tomato (Maxifort or Unifort) and eggplant (Black Beauty). Both moderate (25 µm) and high (50 µm) concentration of Cd in root environment considerably decreased the fruit yield and fruit number in response to Cd levels, whereas mean fruit weight decreased but was similar to both Cd supply levels. The fruit yield, shoot and root biomass, and leaf area (LA) were higher in plants grafted onto tomato rootstocks and especially onto Maxifort in comparison with nongrafted or self-grafted plants and especially grafted onto Black Beauty. The higher plant performance of tomato rootstock–grafted plants were related to higher chlorophyll fluorescence and photosynthetic pigments concentration in leaves associated with better nutrient translocation and availability (higher Ca, Mg, Fe, Mn, and Cu) in leaves. The content of Cd was also lower in leaves and fruits of Maxifort-grafted plants. Concerning fruit quality, especially peel color, toxicity symptoms, and Cd concentration, Black Beauty followed by Maxifort-grafted plants were better than the other grafting combinations. However, plants grafted onto Black Beauty rootstock resulted in lowest fruit yield and plant growth attributes due to lower nutrient uptake and translocation indicating some incompatibility reaction between Black Beauty rootstock and Ikram scion.
Quantifying the Relationship between Leaf Nitrogen Content and Growth Dynamics and Yield of Muskmelon Grown in Plastic Greenhouse
Authors: Yang Xiaofeng , Li Gang , Luo Weihong , Chen Lili , Li Shaopeng , Cao Ming , Zhang Xuebin
Published: February 2019

The aim of this study was to quantitatively investigate the impacts of nitrogen on growth dynamics and yield, so as to facilitate the optimization of nitrogen management for muskmelon crop in plastic greenhouse. For this purpose, four experiments with different levels of nitrogen treatment and planting dates on muskmelon (Cucumis melo L. ‘Nanhaimi’ and ‘Xizhoumi 25’) were conducted in plastic greenhouse located at Sanya from Nov. 2012 to Sept. 2014. The quantitative relationship between leaf nitrogen content and growth dynamics and yield of muskmelon was determined and incorporated into a photosynthesis-driven crop growth model (SUCROS). Independent experimental data were used to validate the model. The critical leaf nitrogen content at flowering stage for muskmelon ‘Nanhaimi’ and ‘Xizhoumi 25’ were 19.8 and 21.0 mg·g−1. The coefficient of determination (r2) and the relative root-mean-squared error (rRMSE) between the predicted and measured value of growth dynamics and yield were, respectively, 0.91 and 10.8% for leaf area index (LAI), 0.90 and 19.6% for dry weight of shoot (DWSH), 0.76 and 30.3%, 0.82 and 21.1%, and 0.92 and 11.9% for dry weight of leaf (DWL), stem (DWST), and fruit (DWF), 0.91 and 17.3%, 0.89 and 13.9%, 0.86 and 27.8%, and 0.88 and 20.6% for soluble sugar content (SU), soluble protein content (PR), vitamin C content (VC), and soluble solids content (SO) of fruit, and 0.90 and 10.1% for fresh weight of fruit (FWF). The model could be used for the optimization of nitrogen management for muskmelon production in plastic greenhouse. Further calibration and test would be needed during the application of the model in wider range of conditions and muskmelon cultivars.
Nitrogen Accumulation and Loss in a High-input Greenhouse Vegetable Cropping System Elevated by Application of Manures
Authors: Quan Zhi , Huang Bin , Lu Caiyan , Shi Yi , Cao Yanhong , Wang Yongzhuang , He Chuanrui , Chi Guangyu , Ma Jian , Chen Xin
Published: February 2019

Much nitrogen (N) is lost in high-input protected cropping systems mainly via leaching of not only nitrate-N but also extractable organic N (EON), but the role of EON in this process is poorly appreciated. A consecutive 3-year plot experiment was conducted to investigate the impact of co-application of manures with chemical N fertilizer on N accumulation and loss in a greenhouse soil rotationally planted with cucumber or tomato and lettuce. Application of manures significantly enhanced the average contents and stocks of NO3−-N, EON, and total N (TN) in 0- to 60-cm soil layer, although EON accumulated within growing season, while NO3−-N accumulated with fluctuation, and TN accumulated gradually throughout the 3-year experiment. With application rate at 120 or 180 t dry manures per hectare per 3 years, the corresponding apparent N surplus was 2710 or 3924 kg⋅ha−1 per 3 years. Due to little increase of biomass N uptakes during vegetable seasons, the accumulated N in soil profile would be a potential loss source, largely via leaching of both nitrate and EON. Application of manures slowed soil acidification but intensified secondary salinization of the greenhouse soil. Considering the manures-induced high soil N accumulation and loss, well-balanced evaluation of the role of manures in high-input agricultural ecosystems is needed.
Impact of Tillage and Irrigation Management on Bell Pepper (Capsicum annuum L.) Grown in Organic and Conventional Production Systems
Authors: Wang Zheng , Williams Mark , Jacobsen Krista , Coolong Timothy
Published: February 2019

Trials were conducted in 2011 and 2012 with ‘Aristotle’ bell pepper (Capsicum annuum L.) grown under different tillage methods and irrigation regimes in organically and conventionally managed production systems. Treatments consisted of strip tillage or plastic mulch in well-watered or water-restricted irrigation regimes. Within organic and conventional production systems, the study was arranged as a split-plot randomized block design with strip tillage or plastic mulch as the main plot and irrigation regime as subplot. Leaf water potential (ΨL), soil penetration resistance (compaction), volumetric water content (VWC), soil temperature, and pepper yield were measured. Soil VWC was greater in strip-tillage plots compared with plastic mulch plots under both well-watered and water-restricted conditions for plots in the organic system in 2011 and conventional system in 2012. In addition, soil VWC was numerically lower, if not always statistically different, in water-restricted plots compared with well-watered plots. The trend of soil temperatures within each production system were similar in 2011 and 2012, with plastic mulch plots having slightly higher soil temperatures than strip tillage, despite using white-on-black plastic mulch. Midday ΨL was affected by water regime, with well-watered plants having a significantly lower ΨL than water-restricted plants; however, there were no effects of irrigation on predawn ΨL. Tillage method and sampling location (between row and within row) significantly interacted to affect soil penetration resistance in 2011 and 2012. There was a significant interaction of tillage by irrigation regime on yield within conventional systems in both years, but not in organically managed plots. In 2011, yield data also indicated that the date at which 50% of marketable fruit were harvested (yield_mid) were later for strip–tillage-grown plants than plastic mulch–treated plants within conventional and organic production systems, respectively.
Development of a Rapid Screening Method for Selection Against High Temperature Susceptibility in Garden Roses
Authors: Greyvenstein Ockert , Starman Terri , Pemberton Brent , Niu Genhua , Byrne David
Published: February 2019

The decline of garden rose sales over the past 20 years can be partially attributed to the lack of material adapted to a wide range of landscapes, which includes adaptation to high temperature stress. Current methods for evaluating high temperature susceptibility in garden roses are based on field observations, which are time consuming and subjected to ever-changing environmental conditions. A series of experiments were conducted to optimize protocols and compare the use of chlorophyll fluorescence (CFL) and cell membrane thermostability (MTS) by way of electrolyte leakage as methods to screen for high temperature susceptibility. Immature leaves proved better than mature leaves for both CFL and MTS measurements, using either detached leaf or whole plant stress assays. MTS measured on immature leaves stressed in a water bath at 50 °C for 45 minutes proved most consistent in separating rose clones based on high temperature susceptibility. Stressing actively growing plants with flower buds of 2 mm in diameter in a heat chamber at 44 °C for 3 hours resulted in increased flower abscission and leaf necrotic lesions on more susceptible clones when compared with those that were heat tolerant. Combining MTS measurements from immature leaves stressed in a water bath with the flower abscission and leaf necrosis responses 10 days after stress in a heat chamber could be the first step to screen and select against the more susceptible clones in a garden rose breeding program. Power analyses suggest that the proposed MTS protocol would be efficient in detecting differences between clones when the difference in electrolyte leakage is greater than 10%.
Production of Interspecific Hybrids between Hydrangea macrophylla and Hydrangea arborescens via Ovary Culture
Authors: Cai Ming , Wang Ke , Luo Le , Pan Hui-tang , Zhang Qi-xiang , Yang Yu-yong
Published: February 2019

Hydrangea macrophylla is the most popular species in the genus Hydrangea because of its large and brightly colored inflorescences. Since the early 1900s, numerous cultivars with showy flowers have been selected. Although many H. macrophylla cultivars have been developed, cold hardiness is still the major limitation to their outdoor use. Hydrangea arborescens is a small attractive shrub or subshrub native to northeastern parts of the United States, which is valued for its hardiness. Interspecific breeding of H. arborescens and H. macrophylla has been tried, but putative hybrid seedlings either died at an early stage or were not verified. We made successful hybridizations between H. macrophylla ‘Blue Diamond’ and H. arborescens ‘Annabelle’ and used in vitro ovary culture to produce viable plants. Hybrids were intermediate in appearance between parents, but variable in leaves, inflorescences, and flower color. The success of this hybridization was confirmed by six simple sequence repeat (SSR) genetic markers. The maternal chromosome number was 36, and the paternal number was 38. Chromosome counts of hybrids indicated that nearly half of them were aneuploids. Male fertility of progeny was evaluated by fluorescein diacetate staining of pollen. Twelve out of 14 hybrids (85.7%) had male fertility. We documented the first flowering progeny of H. macrophylla and H. arborescens, suggesting an effective beginning to a cold hardiness breeding program.
Effects of Three Conservation Tillage Strategies on Yields and Soil Health in a Mixed Vegetable Production System
Authors: Pieper Jeffrey R. , Brown Rebecca Nelson , Amador José A.
Published: February 2019

Most vegetable farms in southern New England market directly to consumers and are characterized by high crop diversity and intensive cultivation. Growers rely on tillage to prepare fields for planting and control weeds, but are concerned about the negative effects of tillage on soil health. This study evaluated three tillage reduction strategies in a market garden system producing tomatoes, melons, cucumbers, cabbage, carrots, and lettuce. Treatments of strip tillage into a killed cereal rye (Secale cereale) cover crop mulch, perennial white clover (Trifolium repens), and ryegrass (Lolium perenne) living mulch between planting rows, and annual crimson clover (Trifolium incarnatum) living mulch interseeded between vegetable rows were established in 2010 and compared over 3 years to a control system using tillage to maintain bare ground between rows. Treatments were evaluated for effects on vegetable yield and soil biological, chemical, and physical properties. The strip tillage treatment was the most effective at promoting soil health, resulting in significant increases in soil aggregate stability, potentially mineralizable nitrogen, active soil carbon, and microbial activity relative to the control, and significant decrease in loss of soil organic matter. However, it was not effective for production of vegetables, with the strip-tillage plots having the lowest yields throughout the study. The perennial living mulch treatment produced yields of carrots, melons, and cucumbers similar to the control yields, but reduced yields of tomatoes, cabbage, and lettuce. Microbial respiration was significantly higher than in the control, and nitrate levels, and loss of soil organic matter were significantly lower. The annual living mulch treatment produced yields similar to the control for all crops, and soil health was similar to the control for all variables except soil nitrate, which was significantly higher than the control. Perennial living mulch shows the most promise for improving soil health while maintaining yields in some vegetable crops, but challenges remain in preventing competition between vegetables and living mulches.
Goss’s Wilt Incidence in Sweet Corn Is Independent of Transgenic Traits and Glyphosate
Authors: Williams Martin M. , Bradley Carl A. , Duke Stephen O. , Maul Jude E. , Reddy Krishna N.
Published: February 2019

Recently, claims have been made that the use of glyphosate and transgenic crop traits increases plant susceptibility to pathogens. Transgenic traits used widely for years in dent corn are now available in commercial sweet corn cultivars, specifically, the combination of glyphosate resistance (GR) and Lepidoptera control (Bt). The objective was to assess the interactions of the GR+Bt trait, glyphosate, and Goss’s wilt on sweet corn. Nine treatments were tested under weed-free conditions at two sites in 2013 and 2014. Treatments included two isogenic cultivars differing only in the presence or absence of GR+Bt, with and without postemergence application of glyphosate, and inoculation with the causal agent of Goss’s wilt (Clavibacter michiganensis ssp. nebraskensis) before glyphosate application, after glyphosate application, or no inoculation. Results failed to show glyphosate or the GR+Bt trait influenced sweet corn susceptibility to Goss’s wilt. The only factor affecting Goss’s wilt incidence was whether plants were inoculated with C. michiganensis ssp. nebraskensis. In the absence of glyphosate application, yet under weed-free conditions, several yield traits were higher in sweet corn with the GR+Bt trait. Results showed that the GR transgene confers the same level of tolerance to glyphosate in sweet corn as observed previously in dent corn. If true, recent claims about glyphosate and transgenic traits increasing plant disease would be of major concern in sweet corn; however, no relationships were found between the GR+Bt trait and/or glyphosate to Goss’s wilt incidence in sweet corn.
Luther Burbank: Plant Breeding Artist, Horticulturist, and Legend
Authors: Janick Jules
Published: February 2019

Luther Burbank (1849–1926), the best-known horticulturist in the United States, was honored in 1940 by having a U.S. postage stamp in his honor—as a scientist! Burbank became a legend in his time as the plant inventor and horticultural wizard releasing a prodigious 800 new cultivars, a number of which are still being grown, the most famous being the ‘Burbank’ potato, the ‘Santa Rosa’ plum, and the ‘Shasta’ daisy. During his lifetime he was considered as a coequal with Henry Ford, inventor of the assembly line factory, and Thomas A. Edison, inventor of the light bulb and phonograph. Hugo de Vries, Liberty Hyde Bailey, and Nikolai Ivanovich Vavilov visited him and lauded his operation. Burbank promoted the concept that plant breeding could be the basis of a business and his headquarters in Santa Rosa, CA, became world famous. He established a publication company to disseminate his work and was instrumental in the eventual passage of the Plant Patent Act of 1930. However, Burbank was not a scientist. Although a strong supporter of Darwin and the theory of natural selection, he did not understand the contributions of Mendel to genetics and breeding. He performed no experiments in the classical sense and his notes were fragmentary. In 1904, he received a large grant from the Carnegie Institution ($10,000 annually) to promote the scientific study of plant breeding, which was discontinued after 5 years when the reviewer, George Harrison Shull, determined that Burbank’s procedure was more art than science. However, Burbank is justly famous as a successful plant breeder. He intuitively followed the modern rationale of plant breeding by obtaining abundant diversity, using repeated and successive hybridization, and carrying out rigorous selection. Above all he had an eye and feel for plants. His success is an affirmation that plant breeding is an art as well as a science. As an innovative plant breeding artist, Luther Burbank remains an inspiration to plant breeders and horticulturists.
Russet Burbank: No Ordinary Potato
Authors: Brown Charles R.
Published: February 2019

The ‘Russet Burbank’ potato cultivar currently occupies first place in acreage planted in North America and is worth in the United States $1.4 billion annually. It is a sport of ‘Burbank's Seedling’, which was selected by Luther Burbank in 1873. The ancestry of Burbank stems from a plant introduction brought to the United States by the Rev. Chauncey Goodrich of New York State in 1853. The priorities of potato breeding had been transformed by repetitive crop failures caused by the emergence of the plant pathogen Phytophthora infestans. Modern testing suggests that derivatives of Goodrich’s potatoes were slightly more resistant to Phytophthora. Burbank discovered a single fruit on one of these derivatives, ‘Early Rose’, in his mother’s garden. Taking the 23 true seeds, he nursed them to full-sized plants and selected ultimately No. 15. It produced an unusually high yield of large, very oblong tubers, stored well, and was a good eating potato. Burbank’s life was destined for a long career in California and he attempted to sell the clone to J.H.J. Gregory of Gregory’s Honest Seeds, a successful businessman. Ultimately Gregory agreed to buy it for $150, far less than Burbank wanted, but enough to propel him to California. Gregory named the potato ‘Burbank's Seedling’, which no doubt engendered fame for the entrepreneur. Luther Burbank had been allowed by Gregory to keep 10 tubers, which became the seed source for the ‘Burbank's Seedling’ to spread north and south along the West Coast of North America with a crop value, stated by Burbank, of $14 million in 1914. It is not clear that Luther Burbank prospered from ‘Burbank's Seedling’ in the West. A skin sport with a russet skin was found in Colorado in 1902 and was advertised by a seed company under the name ‘Netted Gem’. ‘Burbank's Seedling’ per se disappeared from commerce and ‘Netted Gem’ slowly increased, finding a special niche in production of French fry potatoes. It is clear that Luther Burbank gained tremendous insight into the dynamics of hybridization in revealing genetic variation from clonally propagated species. During the rest of his career he would use this technique to produce new and amazing forms of numerous food and ornamental species. ‘Burbank's Seedling’ was his entrez into the world of plant breeding.