bluuebunny/crossref_metadata_2025 huggingface dataset:
Black Walnut: A Nut Crop for the Midwestern United States
Authors: Coggeshall Mark V.
Published: February 2019

Eastern black walnut (Juglans nigra L.), is a native tree species valued both for its timber and nuts. Individual trees require excellent soils with adequate moisture for maximum wood and nut productivity. The vast majority of black walnut nutmeat production is centered in the western part of the species’ native range and is predominantly derived from wild, unimproved sources. Historically, the size of this crop has ranged from 4.5 to 15.9 million kilograms (fresh weight, without hull) with less than 1% obtained from improved cultivars. Alternate bearing is common in this species, primarily as a result of susceptibility to walnut anthracnose Gnomonia leptostyla (Fr.) Ces. & De Not. Significant reductions in nut productivity caused by walnut curculio (Conotrachelus retentus Say) are common for unimproved, wild trees. Based on a collection of 65 nut cultivars established by the University of Missouri, black walnut exhibits significant genetic variation for a range of commercially important nut traits, including precocity, percent kernel, nut bearing habit, anthracnose tolerance, season length, and yield efficiency. Exploiting this variation through traditional plant breeding techniques will result in new, improved varieties in the future. Defining improved cultural practices that will significantly impact yield and nut quality remains an area of active investigation. Such knowledge will need to be combined with improved cultivars that are well adapted to local growing conditions to ensure the commercial success of this species over the long run.
Low Night Temperature Increases Ovary Size in Sweet Pepper Cultivars
Authors: Cruz-Huerta Nicacio , Williamson Jeffrey G. , Darnell Rebecca L.
Published: February 2019

Cool night temperatures have been reported to induce ovary swelling and consequent fruit deformation in bell pepper (Capsicum annuum L.), resulting in unmarketable fruit. This response is a serious limitation to the success of winter production systems for bell pepper. Limited work has been done with other types of sweet pepper, so it is unknown how universal this response is. Furthermore, most prior work has examined effects on ovary diameter only, and there is limited characterization of other ovary traits in response to cool night temperature. The objectives of the present study were to determine the effects of low night temperature on ovary characteristics in different sweet pepper cultivars and to determine the parts of the ovary that are most affected by these factors. Three types of sweet pepper (bell, long-fruited, and cherry) were exposed to 22/20 or 22/12 °C day:night temperatures and flowers at anthesis were continuously harvested throughout the experiments. Ovary fresh weight (FW), diameter, and length across all types (and cultivars within type) were greater under 22/12 °C compared with 22/20 °C. The increase in ovary FW was the result of increases in both ovary wall and placenta FW. In general, all cultivars exhibited increases in ovary size under 12 °C compared with 20 °C night temperature. Differences in ovary FW resulting from night temperature became more pronounced with time. These results indicate that low night temperature effects on ovary swelling may be a universal response among sweet pepper types. Three to 4 weeks are required for maximum swelling response, suggesting that flower buds must be exposed to low night temperatures within the first week after flower bud initiation, because previous work found that flower bud initiation in bell pepper takes ≈4 weeks. However, the duration of low night temperatures necessary for this response remains unknown.
Vigor Tests to Estimate Seedling Emergence Potential and Longevity in Viola Seed Lots
Authors: Demir Ibrahim , Celikkol Tuba , Sarıkamıs Golge , Eksi Ceren
Published: February 2019

A study was made of the relationship among accelerated aging (AA), saturated salt accelerated aging (SSAA), mean germination time and second day germination percentage vigor tests, and seedling emergence and longevity storage at 5 and 25 °C for 6 and 12 months. Initial germination was above 80% for all seed lots. Seedling emergence values varied between 21% and 94% and mean emergence time between 6.5 and 11.0 days among seed lots. The SSAA test correlated with emergence better than the AA test. All combinations of SSAA temperatures (41, 43, and 45 °C for 72 h) were correlated to emergence (r = 0.95 to 0.98, P < 0.001) and emergence rate (r = 0.90 to 0.94, P < 0.001). Seed germination after 6 months of storage ranged between 21% and 98% at 5 °C and 26% and 100% at 25 °C. Corresponding values were 19% and 98% and 15% and 89% after 12 months. All combinations of AA and SSAA were related to longevity of seed lots, but significance for SSAA was higher (above P < 0.01) than AA (P < 0.05). In both tests, a higher aging temperature reduced the significance level. Mean germination time and second day germination percentages also predicted seedling emergence and longevity (P < 0.05 in all cases). Standard germination percentages were successful in predicting seedling emergence (P < 0.05), but with one exception failed to predict (P > 0.05) longevity in viola seed lots. In conclusion, although both aging tests successfully differentiated seed quality, SSAA test results better predict emergence and longevity of viola seed lots.
The Dynamic Model Provides the Best Description of the Chill Process on ‘Sirora’ Pistachio Trees in Australia
Authors: Zhang Jianlu , Taylor Cathy
Published: February 2019

Determining the chilling requirement for ‘Sirora’ pistachio (Pistacia vera L.) production in Australia and monitoring winter chill accumulation is desirable to allow growers to take timely mitigating action in years of insufficient chill. Based on greenhouse work, historical data analysis, and field validation, the Chilling Hour, Utah, and Dynamic Models were compared. The Dynamic Model produced the best determination for fulfillment of chilling requirement with 59 chill portions. The required number of growing degree-hours above 4.4 °C from chill fulfillment to 50% bloom was 9633. Relations among the level of fulfillment of chilling requirement, bloom delay, and yield are discussed.
Fluorescent Illumination with High Red-to-far-red Ratio Improves Resistance of Cucumber Seedlings to Powdery Mildew
Authors: Shibuya Toshio , Itagaki Kaori , Tojo Motoaki , Endo Ryosuke , Kitaya Yoshiaki
Published: February 2019

We investigated the effects of fluorescent illumination with a high red-to-far-red ratio (R:FR) on the resistance of cucumber (Cucumis sativus) seedlings to powdery mildew fungus (Sphaerotheca cucurbitae; PM). Seedlings were grown at a photosynthetic photon flux (PPF) of 300 μmol·m−2·s−1 provided by fluorescent lamps with high R:FR light (R:FR = 7.0; FLH) or low R:FR light (R:FR = 1.1; FLL) until cotyledons or the first foliage leaf were fully expanded. Spores of PM were then inoculated onto the leaves, and the seedlings were grown for 7 days (from cotyledon stage) or 9 days (from foliage–leaf stage) under FLH. The number of PM colonies on FLH seedlings was 0.80× (cotyledons) and 0.62× (foliage leaves) the number on FLL seedlings. The reduction on the FLH seedlings was probably the result of changes in leaf morphological characteristics such as a thicker epidermal tissue as a result of the higher R:FR illumination. The number of PM colonies on cotyledons of the FLH seedlings was also smaller than that on seedlings grown under metal-halide lamps providing a spectrum similar to that of natural light (R:FR = 1.2).
Ethephon as a Blossom and Fruitlet Thinner Affects Crop Load, Fruit Weight, Fruit Quality, and Return Bloom of ‘Summerred’ Apple (Malus ×domestica) Borkh.
Authors: Meland Mekjell , Kaiser Clive
Published: February 2019

‘Summerred’ apples (Malus domestica Borkh.) are highly susceptible to biennial bearing if not properly thinned. This results in erratic yields and also affects fruit quality adversely. Between 2003 and 2005, ‘Summered’/‘M9’ trees were treated with ethephon at concentrations of 250, 375, and 500 mg·L−1 when most king flowers opened (≈20% bloom) or at concentrations of 500, 625, and 750 mg·L−1 when the average fruitlet size was 10 mm in diameter. The experiment was conducted with 2.5-m height slender spindle trees sprayed to the point of runoff with a hand applicator only when temperatures exceeded 15 °C. Within 2 weeks after the second application, fruit set was reduced linearly with increasing concentrations of ethephon to less than one fruitlet per cluster at the highest concentrations used. Most thinning treatments reduced fruit set significantly compared with unthinned trees. Fruit numbers per tree decreased significantly with increasing ethephon concentrations, and the highest concentrations of ethephon applied during bloom or when the average fruitlet size was 10 mm in diameter resulted in overthinning. Yield results confirmed the fruit set response in which yield reductions were significant at the highest concentrations of ethephon (2.1 kg/tree) compared with hand-thinned trees (7.3 kg/tree) in 2005. All thinning treatments resulted in higher percentage of fruits larger than 60 mm diameter compared with unthinned control fruit. Thinning resulted in significantly higher soluble solid contents, and this was especially so for hand-thinned trees. Other fruit quality parameters like yellow–green background color did not show a clear response to thinning. Return bloom was, however, improved on all thinned trees. It is recommended that ethephon be applied at a rate of 375 mg·L−1 when king flowers open or at a rate of 625 mg·L−1 when the average fruitlet size is 10 mm in diameter. This thins ‘Summerred’ apples to a target of approximately five fruits/cm2 per trunk cross-sectional area or 50 to 70 fruits per 100 flower clusters without impacting on fruit quality, yield, or return bloom the next year.
Oleocellosis Injury of Fruitlets from Late-season Mechanical Harvesting of ‘Valencia’ Orange Trees after Different Irrigation Treatments Does Not Affect Internal Fruit Quality
Authors: Melgar Juan Carlos , Dunlop Jill M. , Syvertsen James P.
Published: February 2019

Oleocellosis or oil spotting on the peel of citrus fruit is a common post-harvest injury caused by improper handling. Mechanical injury allows phytotoxic oil to leak out of oil glands and cause injury to surrounding flavedo cells, resulting in oleocellosis. Mechanical harvesting (MH) of ‘Valencia’ sweet orange is conducted in late spring, when the next season's fruitlets are in their early stages of development. There is a concern that mechanical injury from harvesting machines can cause oleocellosis and fruit drop of young, green ‘Valencia’ sweet orange fruitlets, especially late in the harvest season when fruitlets are relatively large. We evaluated the effects of winter drought stress and subsequent late-season MH with a canopy shaker on oleocellosis of ‘Valencia’ sweet orange fruitlets. In April, mature fruit size, juice content, total soluble solids, and acidity were unaffected by previous winter drought stress treatments. Mechanical harvesting removed ≈90% to 95% of mature fruit and 20% to 50% of fruitlets depending on previous drought stress treatments and harvesting date. Beginning 1 week after the late harvest (13 June), attached fruitlets were tagged and visually evaluated approximately every other month to determine oleocellosis injury until the late-season harvest 12 months later. Only 12% of the fruitlets had oleocellosis on more than 30% of their surface area. Up to 75% of the fruitlets from the previously drought-stressed trees had less than 10% of their surface area injured after MH and 11% of these fruitlets dropped before harvest. Nonetheless, there was no significant increase in fruit drop with increased surface area injured nor was juice quality affected at harvest. Overall, fruit surface oleocellosis decreased and healed as fruit expanded, but surface blemishes did not completely disappear. Thus, fruitlet oleocellosis in late-season mechanically harvested trees was cosmetic and did not increase fruit drop nor alter internal fruit quality.
Water Deficit Affects the Accumulation of Capsaicinoids in Fruits of Capsicum chinense Jacq.
Authors: Ruiz-Lau Nancy , Medina-Lara Fátima , Minero-García Yereni , Zamudio-Moreno Enid , Guzmán-Antonio Adolfo , Echevarría-Machado Ileana , Martínez-Estévez Manuel
Published: February 2019

The pungency of chili peppers is conferred by compounds called capsaicinoids that are produced only in the fruits of the Capsicum genus. Accumulation of capsaicinoids in these fruits may be affected by environmental conditions such as water and nutrient stresses, although these effects may vary even among genotypes within a species. The Habanero pepper (Capsicum chinense Jacq.), grown in the Yucatán, is in especially high demand as a result of its unique flavor, aroma, and pungency and is the second most important commercial crop in the state after the tomato. Although the Habanero pepper is a significant economic resource for the region, few studies have investigated the effects of abiotic stresses on capsaicinoid production. In this study, the effects of water stress on plant growth, capsaicinoid accumulation, and capsaicin synthase activity were evaluated. Habanero pepper plants under water stress had a lower height, root dry weight, and root/shoot relation than control plants, which were irrigated daily. However, fruit growth and production were unaffected by water stress. Capsaicin and dihydrocapsaicin concentrations increased in fruits of stressed plants compared with control plants, and this effect was correlated with fruit age. However, capsaicin synthase activity was reduced in response to water stress, and this effect depended on both stress severity and fruit age. These results provide new information on the regulation of capsaicinoid metabolism in response to abiotic stress from the fruit of a highly pungent chili pepper.
Moisture Content of Extensive Green Roof Substrate and Growth Response of 15 Temperate Plant Species during Dry Down
Authors: Bousselot Jennifer M. , Klett James E. , Koski Ronda D.
Published: February 2019

Success of extensive green roof vegetation depends primarily on associated plant species' ability to survive the low moisture content of the substrate. As a result of the well-drained nature of the substrate, plants adaptable to dry, porous soils are primarily used in extensive green roof applications. Although Sedum species have dominated the plant palette for extensive green roofs, there is growing interest in expanding the plant list for extensive green roof systems. To effectively select suitable plants, species need to be evaluated in terms of their response to gradual and prolonged dry down of the substrate. A study to determine the relative rates of dry down for 15 species was conducted in greenhouse trials. During dry downs that extended over 5 months, the substrate of succulent and herbaceous species dried down at different rates. The change in moisture content of the substrate was not consistent among succulent and herbaceous plant species during the initial 18 d of dry down. Despite differences in rate of dry down, the succulent species, as a group, maintained viable foliage for over five times longer than the herbaceous species. The revival rates of the succulent species were nearly double those of the herbaceous species. Therefore, not only are succulent species more likely to survive during periods of drought, but these species are more likely to resume growth soon after water is again made available.
Nutrient Accumulation and Flower Bud Formation Affected by the Time of Terminal Bud Set on Water Sprouts of Persimmon
Authors: Choi Seong-Tae , Park Doo-Sang , Kang Seong-Mo
Published: February 2019

Heavy pruning to lower tree height of persimmon results in excessive production of water sprouts and reduced yield. This experiment was conducted on ‘Fuyu’ (Diospyros kaki) trees to assess if the time for terminal bud set of water sprouts affected flower bud formation. Some sprouts were not pruned to serve as fruiting branches for the next season. Thirty to 40 water sprouts were tagged in 2005 and 2006, the growth of which stopped from mid-June to late August. The later terminal buds set, the lower the percent dry weight in the apical 10 cm. The apical segments of sprouts that continued to grow to mid- to late August were characterized by low soluble sugars, starch, and inorganic elements such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) compared with those that set terminal buds earlier. The number of flower buds from the water sprouts that set terminal buds by early August the previous year bore more than 12 flower buds the next year, whereas those that grew to mid- to late August bore fewer than three. It was concluded that water sprouts could be used as fruiting branches for the next year as long as terminal buds set by early August, thereby alleviating yield reductions that come with heavy pruning.
Screening of Cucurbita moschata Duchesne Germplasm for Crown Rot Resistance to Floridian Isolates of Phytophthora capsici Leonian
Authors: Chavez Dario J. , Kabelka Eileen A. , Chaparro José X.
Published: February 2019

Phytophthora capsici causes seedling death, crown and root rot, fruit rot, and foliar blight on squash and pumpkins (Cucurbita spp. L.). A total of 119 C. moschata accessions, from 39 geographic locations throughout the world, and a highly susceptible butternut squash cultivar, Butterbush, were inoculated with a suspension of three highly virulent P. capsici isolates from Florida to identify resistance to crown rot. Mean disease rating (DR) of the C. moschata collection ranged from 1.4 to 5 (0 to 5 scale with 0 resistant and 5 susceptible). Potential resistant and tolerant individuals were identified in the C. moschata collection. A set of 18 PIs from the original screen were rescreened for crown rot resistance. This rescreen produced similar results as the original screen (r = 0.55, P = 0.01). The accessions PI 176531, PI 458740, PI 442266, PI 442262, and PI 634693 were identified with lowest rates of crown infection with a mean DR less than 1.0 and/or individuals with DR = 0. Further selections from these accessions could be made to develop Cucurbita breeding lines and cultivars with resistance to crown rot caused by P. capsici.
Historical Trends in Strawberry Fruit Quality Revealed by a Trial of University of Florida Cultivars and Advanced Selections
Authors: Whitaker Vance M. , Hasing Tomas , Chandler Craig K. , Plotto Anne , Baldwin Elizabeth
Published: February 2019

The University of Florida strawberry (Fragaria ×ananassa Duch. ex Rosier) breeding program has maintained a continuous breeding effort since 1968 to develop cultivars that are highly adapted to winter production in west-central Florida. To gain insight into breeding progress over time, two advanced selections (UF1 and UF2) and 10 released cultivars, from Florida Belle (1975) to Florida Radiance (2008), were compared for various fruit quality traits in a two-location field study during the 2009–2010 season. Fruit size varied dramatically from 30.8 g for ‘Elyana’ to 16.2 g for ‘Dover’ at Balm, FL, and from 28.3 g for UF2 to 16.6 g for ‘Dover’ at Dover, FL. A linear regression of fruit size on year of release revealed an average gain of 2.6 g per year since 1975 for the cultivars and selections tested (R2 = 0.44). A similar analysis revealed a reduction over time in the proportion of cull fruit (R2 = 0.30). Gains were apparent for the redness of the internal flesh, from a colorimeter a* value of 16.1 for ‘Florida Belle’ (1975) to 34.7 for ‘Carmine’ (2002) but were not sustained for later releases and selections. Although there were significant differences among genotypes for all chemical traits affecting flavor, there were no discernable patterns over time. There were wide month-to-month variations in individual sugars and organic acids, except for citric acid, which was stable across months and locations. The ratio of soluble solids content to titratable acidity ranged widely among genotypes, from a high of 15.7 for ‘Florida Belle’ in February at Dover, FL, to a low of 6.4 for ‘Winter Dawn’ in January at Balm, FL. The observed variability and trends in fruit quality traits will help guide future genetic studies and inform decisions about future breeding priorities and selection procedures.
Optimization of In Vitro Pecan Pollen Germination
Authors: Conner Patrick J.
Published: February 2019

Storage of pollen from 1 year to the next is often needed to enable desired crosses to be made in a pecan [Carya illinoinensis (Wangenh.) K. Koch] breeding program. Stored pollen is usually tested for viability through the use of in vitro germination tests. An in vitro germination testing system was developed for this purpose using cellophane booklets to provide a solid support for the pollen grains. Optimized germination media contained 5% sucrose, 20% polyethylene glycol 8000, 0.05% Ca(NO3)2, 0.025% H3BO3, and 10 mm 2-(N-morpholino)ethanesulfonic acid pH 6.0. Pollen should be rehydrated for 2 to 4 h in a humidified chamber before germination testing. A germination time of 4 to 24 h produces similar final germination percentages. Testing of pollen samples stored at –80 °C indicates that pecan pollen can be stored for at least 8 years without a decrease in viability. Chemical names used: polyethylene glycol (PEG); 2-(N-morpholino)ethanesulfonic acid (MES).
Applications of a Commercial Extract of the Brown Seaweed Ascophyllum nodosum Increases Drought Tolerance in Container-grown ‘Hamlin’ Sweet Orange Nursery Trees
Authors: Spann Timothy M. , Little Holly A.
Published: February 2019

‘Hamlin’ sweet orange trees on ‘Carrizo’ citrange and ‘Swingle’ citrumelo rootstocks were treated weekly with a commercial extract of the brown seaweed Ascophyllum nodosum at 5 and 10 mL·L−1 as either a soil drench or foliar spray. Half of the trees in each treatment were subjected to drought stress [irrigated at 50% of evapotranspiration (ET)], whereas the other half remained fully irrigated (100% ET). Drought stress reduced shoot growth and leaf photosynthesis but increased root and total plant growth relative to the amount of water applied, thus increasing whole plant water use efficiency. Trees treated with seaweed extract and drought-stressed had significantly more total growth than untreated drought-stressed trees for both rootstocks. The maintenance of growth by the seaweed extract under drought stress conditions was unrelated to photosynthesis. However, the seaweed extract treatment did have a significant effect on plant water relations. Soil drench-treated trees had more growth and higher stem water potential than foliar-treated or control trees after 8 weeks of drought stress. These results indicate that seaweed extract may be a useful tool for improving drought stress tolerance of container-grown citrus trees.
The Effect of Natural Light on Changes in Antioxidant Content and Color Parameters of Vine-ripened Tomato (Solanum lycopersicum L.) Fruits
Authors: Pék Zoltán , Szuvandzsiev Péter , Nemenyi András , Helyes Lajos , Lugasi Andrea
Published: February 2019

During the vine ripening of tomato fruits (Solanum lycopersicum L.), the change in antioxidant content and color was studied under two different solar exposures. An experiment was carried out in 2008 and 2009 to determine how color evolution, surface temperature, and antioxidant content of tomato fruits were influenced by fruit position and exposure on trellised tomato plants. Trellised rows were oriented so that non-shaded fruits were subjected to full solar irradiation from 0900 hr to 1600 hr, whereas shaded fruits were completely shaded during the same time period. A significant difference (P = 0.001) between fruit surface temperatures of shaded or non-shaded fruits was observed. The more direct solar irradiation the fruits were exposed to, the higher the fruit surface temperatures increased. At 1400 hr, only the average temperature of non-shaded fruits was significantly higher (7.0 and 9.3 °C in 2008 and 2009, respectively) than the air temperature. At the end of the ripening process, color change of non-shaded fruits showed significantly higher CIELab hue compared with shaded fruits. A close negative correlation (R2 = 0.51) was detected between the hue color parameters and the cumulative fruit surface–air temperature difference of non-shaded fruits, but in the case of shaded fruits, there was only a weak (R2 = 0.29) correlation. Solar exposure had a great effect on the antioxidant content of tomato fruits. A higher fruit surface temperature resulted in significantly less lycopene and more polyphenols and ascorbic acid content in tomato fruits.
Influence of Aminoethoxyvinylglycine (AVG) on Yield and Quality of Nut Crops from a Commercial Pecan Orchard
Authors: Wood Bruce W.
Published: February 2019

Excessive fruit drop (i.e., June drop) can limit orchard profitability of certain pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars. The present study examines efficacy of aminoethoxyvinylglycine (AVG; formulated as ReTain®; Valent BioSciences, Libertyville, IL), a natural ethylene inhibitor, for increasing nutmeat yield in a commercial ‘Desirable’ pecan orchard over a 2-year period. The 30-ha experiment consisted of two treatments (nontreated versus ReTain) in the first year, an “off” year in the orchard's alternate bearing cycle. The second year's study, an “on” year, consisted of four treatments (i.e., “08 nontreated + 09 nontreated,” “08ReTain + 09 nontreated,” “08 nontreated + 09 ReTain,” and “08ReTain + 09 ReTain”). AVG, as ReTain [132 mg·L−1 a.i. (11.7 oz/acre)], was applied as two post-pollination canopy sprays (937 L·ha−1) 2 weeks apart in both years. During the “off” year, ReTain increased nut yield parameters with ReTain increasing kernel yield by 36% (704 kg·ha−1 versus 516 kg·ha−1) over that of nontreated trees. In the subsequent “on” crop year, the trees exhibiting a ReTain-associated previous year yield increase of ≈36% exhibited a reduction in yield of ≈25%, thus largely negating the previous season's yield increase over a 2-year alternate bearing cycle. Additionally, ReTain-treated trees during the “on” year failed to exhibit an increase in yield parameters over that of the nontreated control. As a result of a lag effect on subsequent year yield parameters, ReTain offers potential as a crop-load management tool for ‘Desirable’ orchards in “off” years such as a year of relatively high nutmeat price followed by a year of relatively low price. There appears to be no positive effect on yield when used in a heavy crop-load “on” year of an alternate bearing cycle. Thus, ReTain might have benefit for stabilizing alternate bearing in ‘Desirable’ pecan orchards. Kernel quality (defined as percentage of nut weight as kernel) of individual nuts from “on” year trees was not as sensitive to units of yield increase as for individual nuts of “off” year trees, thus implying that the rate of assimilate partitioning to individual reproductive structures in “off”-year trees is not as great as that in “on”-year trees.
Effect of Abscisic Acid and Benzyladenine on Fruit Set and Fruit Quality of Apples
Authors: Greene Duane W. , Schupp James R. , Winzeler H. Edwin
Published: February 2019

Experiments were conducted over a 5-year period to determine the effects of abscisic acid (ABA) and benzyladenine (BA) applied alone and in combination on fruit set, fruit quality, and return bloom of ‘McIntosh’ and ‘Fuji’ apples. ABA thinned in 3 of the 5 years used and it thinned ‘McIntosh’ when applied at bloom, petal fall, and at the 10-mm fruit size stage. On ‘Fuji’, ABA thinned over a range of concentrations from 150 to 1000 mg·L−1. It caused leaf yellowing on ‘McIntosh’ but not on ‘Fuji’. When BA was applied with ABA on ‘McIntosh’, even at a rate as high as 1000 mg·L−1, it either dramatically reduced or prevented leaf yellowing and leaf abscission. The usefulness of applying BA with ABA was inconclusive because of variability in thinning response. ABA advanced surface red color on ‘McIntosh’ and when combined with BA, it reversed the reduction in red color caused by BA.
Development and Evaluation of a Large-volume Rotary Root Separator
Authors: Silva Dilma , Cox Donald , Beeson Richard C.
Published: February 2019

Isolation of plant roots from soil or substrate for biomass measurement is time-consuming and can be a limiting factor influencing experimental designs, especially with mature woody plants. An electric-powered root separator was developed that sped sample preparation for root dry mass determination with a capacity of 40 L of container substrate or 32 kg of sandy soil. No water was required for machine operation and an estimated fourfold reduction in total processing time was achieved. Extent of root recovery was quantified by processing five woody plant species grown in two different container substrates and in soil, resulting in a minimum yield of 98%.
Identification of Citrullus lanatus Germplasm Accessions Tolerant to Clomazone Herbicide
Authors: Harrison Howard F. , Kousik Chandrasekar S. , Levi Amnon
Published: February 2019

Clomazone herbicide is registered for use in watermelon; however, crop tolerance is marginal, and the recommended use rates (0.17 to 0.28 kg a.i./ha) are lower for watermelon than for other crops. In a greenhouse germplasm evaluation experiment including 56 germplasm accessions and watermelon cultivars, three Citrullus lanatus var. citroides PI accessions (PI 482324, PI 5003540, and PI 532624) were not injured by clomazone, whereas most of the other accessions and cultivars were moderately or severely injured. A greenhouse concentration response experiment demonstrated that the clomazone concentration required to cause moderate injury to the tolerant ‘PI 500354’ was approximately three times the concentration required to cause similar injury to the susceptible citroides accession ‘PI 244017’, and the concentration required to cause 50% shoot biomass reduction was approximately five times greater for ‘PI 500354’ than for ‘Charleston Gray’ watermelon. Subsequent field experiments demonstrated that two tolerant accessions (‘PI 500354’ and ‘PI 482324’) were injured less initially by clomazone and recovered more rapidly from clomazone injury than two susceptible accessions (‘PI 244017’ and ‘PI 271773’) and two watermelon cultivars (‘Charleston Gray’ and ‘Crimson Sweet’). Tolerant germplasm accessions like ‘PI 482324’ and ‘PI 500354’ may be useful as sources of clomazone tolerance in watermelon breeding. Chemical name used: clomazone {2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone}.
Productivity, Oil Content, Composition, and Bioactivity of Oil-bearing Rose Accessions
Authors: Kovatcheva Natasha , Zheljazkov Valtcho D. , Astatkie Tess
Published: February 2019

Rose oil production worldwide is based on different oil-bearing Rosa species. This 4-year study determined the essential oil content, constituents, and morphologic/phenologic characteristics of 25 varieties, chemotypes, and hybrids belonging to five Rosa species (R. damascena Mill., R. gallica L., R. centifolia L., and R. alba L.). Limits of variation of these indices were established for each variety, chemotype, and hybrid group. The essential oil content of R. damascena varied from 0.032% to 0.049% and that of hybrid roses from 0.037% to 0.05%. The highest essential oil content was found in R. damascena accession Svejen 74 and the lowest in R. alba. Within R. damascena, the weight of single flowers varied from 2.09 to 3.44 g, the number of petals from 22 to 28, the height of the plants from 61 to 128 cm, and the diameter of bushes from 53 to 118 cm. R. centifolia had the largest flowers. The essential oil of the various species showed moderate to no antimicrobial activity at 50 μg/mL and no significant antibacterial, antifungal, antileishmania, or antimalarial activity at this concentration. All the tested species and accessions could be grown in Bulgaria (and possibly in southeastern Europe and the northern Mediterranean) and provide comparable productivity to the traditional species R. damascena. Wide variations occurred in essential oil content and constituents and morphologic/phenologic characteristics of the tested Rosa species and accessions. The availability of various species and chemotypes within specific species offer an opportunity for production of oil-bearing roses and essential oils to meet market requirements of specific rose oils.
Effect of Container Color on Substrate Temperatures and Growth of Red Maple and Redbud
Authors: Markham John W. , Bremer Dale J. , Boyer Cheryl R. , Schroeder Kenneth R.
Published: February 2019

Heat stress is problematic to root growth in the production of containerized nursery plants. Container color may moderate effects of solar radiation on substrate temperatures. Studies were conducted near Manhattan, KS, to evaluate effects of container color on growth of roots and shoots in bush beans (Phaseolus vulgaris L.), red maple (Acer rubrum L.), and eastern redbud (Cercis canadensis L.). Four treatments among studies included containers colored flat and gloss white, silver, and black; a green container color treatment was added to the tree studies. Plants were grown in bark-based soil-less substrate and temperatures were measured at 5-cm depths in the south sides and centers. After 4 months, plant variables were measured. Roots were separated into three sections: core, north, and south. In the bean study, substrate temperatures at the south side of the container averaged lowest in flat and gloss white (≈36 °C) and greatest in black containers (50.3 °C). Root density at the south side was reduced in beans by 63% to 71% in black compared with flat and gloss white. In heat-sensitive maples, substrate temperatures at the south side of containers averaged up to 7.7 °C greater in black and green than in other treatments. Substrate temperatures in the center averaged 3.5 to 3.8 °C greater in black than in flat and gloss white, resulting in up to 2.5 times greater root density in flat and gloss white than in black containers. In heat-tolerant redbuds, the effects of container color on whole-plant growth were less evident. Data suggest that heat-sensitive plants benefit from being grown in white containers or painting outer surfaces of green and black containers white.
The Effects of Slope and Channel Nutrient Solution Gap Number on the Yield of Tomato Crops by a Nutrient Film Technique System under a Warm Climate
Authors: López-Pozos Roberto , Martínez-Gutiérrez Gabino Alberto , Pérez-Pacheco Rafael , Urrestarazu Miguel
Published: February 2019

Inadequate oxygenation of the nutrient solution (NS) in recirculating hydroponic systems leads to root hypoxia in several plants as a result of low oxygen solubility, and this is most notable in warm climates. Hypoxia affects crop nutrient and water absorption and results in reduced crop yield. However, increased air supply to the NS serves as a source of oxygen for the roots. To evaluate the incorporation of oxygen into the system, we varied the slope of 14-m long containers from 2% to 4% and applied zero, one, two, or three gaps of NS. The channel width measured 10 cm and was equidistant from the end points. The effect of the dissolved oxygen in the NS was measured by the production of a tomato cultivar. The oxygen dissolved in the NS was 5% greater in the channels with a 4% slope compared with those with a 2% slope. The channels that included the gaps incorporated a higher quantity of dissolved oxygen during cultivation. In the middle of the day, the available oxygen was the limiting factor for the yield. The best results were obtained with a steeper slope, and gaps also improved the tomato yield. More rapid changes in NS were associated with a higher quantity of dissolved oxygen.
Generations X and Y Attitudes toward Fresh Flowers as Gifts: Implications for the Floral Industry
Authors: Rihn Alicia L. , Yue Chengyan , Behe Bridget , Hall Charles
Published: February 2019

Demand for fresh-cut flowers and floral products has been decreasing in recent years, particularly among young consumers. The objectives of this study were to explore Generations X and Y's positive and negative attitudes toward flowers as gifts; explore differences in perceptions about price, product, place, and promotions among Generations X and Y to determine the best marketing techniques to reach them; and determine what actions the floral industry can take to improve Generations X and Y's use of flowers as gifts. Participants were recruited in Minneapolis and St. Paul, MN, and Lansing and East Lansing, MI. Participants were asked to complete a questionnaire and participate in a focus group discussion. An ordered probit model was used to analyze the data. Results showed that younger consumers were dissatisfied with several floral product attributes, including short longevity, lack of trendiness, relative high cost, lack of appropriateness, and lack of uniqueness. Results also indicate that younger consumers perceived that their friends do not enjoy floral gifts. Additionally, younger consumers viewed floral advertisements less frequently and considered floral gifts difficult to purchase, resulting in decreased awareness and interest. Overall, most participants felt that in-store sales or discounts, greater flower longevity, more price ranges, and trendier arrangements/flowers would increase their use of fresh flowers as gifts.
Biodigestion of Plant Material Can Improve Nitrogen Use Efficiency in a Red Beet Crop Sequence
Authors: Gunnarsson Anita , Lindén Börje , Gertsson Ulla
Published: February 2019

Nitrogen (N) tied up in or lost from decomposing biomass decreases the residual N effects of green manure and of other crop residues. During anaerobic degradation in a biogas digestor (biodigestion), N mineralization takes place under conditions in which losses can be kept to a minimum. Therefore, biodigestion of green manure biomass and beet foliage was tested to generate readily available N and compared with a direct green manure fertilization system. The effluent was applied as fertilizer in field experiments on a sandy soil as a tool for improving N supply for an organic farming system. Data from the field experiments were used for simulating the amount of net inorganic N equivalents (inorganic N equivalents from effluent plus inorganic N equivalents from pre-crops) in three crop sequences: A) green manure ley, red beets, winter rye; B) harvested ley, red beets, winter rye; and C) harvested ley, spring barley, red beets in which (B) and (C) represented biogas nutrient management systems and (A) a green manure system. When all available effluent from biogas production from 1 ha of grass–clover ley with two or three harvests (2H-ley or 3H-ley) and one hectare of beet foliage was used as a fertilizer for red beets (Beta vulgaris var. conditiva Alef) after barley (Hordeum vulgare L.), the yield of marketable red beets increased by 5.7 Mg·ha−1 (33%) with effluent from 2H-ley and beet foliage and 9.1 Mg·ha−1 (53%) with effluent from 3H-ley and beet foliage compared with red beets grown without effluent fertilization after a green manure ley. When total dry matter production was taken into account, the advantage for the BG systems with 2H- and 3H-ley was 15% and 28%, respectively. The nitrate concentration in the red beets was not higher with effluent supplied at this level than with green manure as the only N source. The simulated amount of net inorganic N equivalents was 128 kg N for the whole of crop sequence (C) with 1 ha of each crop and where effluent supply to red beets was based on digested biomass in ley and beet tops. The corresponding amount of net inorganic N equivalents for the green manure crop sequence (A), in which no effluent was supplied, was 73 kg N. Unused soil mineral N (0- to 90-cm depth) at red beet harvest indicated that the risk of leaching in BG systems was lower than in GrM systems (88, 76, and 61 kg Nmin/ha left after unmanured beets after Gr-M-ley, low manured beets after 3H-ley and high manured beets after barley, respectively). Effluent fertilization of red beets directly after 2H- and 3H-ley gave unexpectedly low yield responses compared with red beets after barley. The reasons may be the result of nutritional imbalance of other nutrients than N or may be plant pathological in nature. The conclusion is that a nutrient management system with biodigestion can increase net inorganic N equivalents and reduce risk for N leaching, but inappropriate use of the effluent, i.e., at an unsuitable point in the crop rotation, may negate the benefits.
Nitrogen:Phosphorus:Potassium Ratios Affect Production of Two Herbaceous Perennials
Authors: Kraus H.T. , Warren S.L. , Bjorkquist G.J. , Lowder A.W. , Tchir C.M. , Walton K.N.
Published: February 2019

A series of experiments were undertaken to determine the effects of nitrogen (N), phosphorus (P), and potassium (K) concentrations and N:P:K ratio on flowering and vegetative growth of two herbaceous perennials, Hibiscus moscheutos L. (hibiscus) and Rudbeckia fulgida var. sullivantii Ait. ‘Goldsturm’ (rudbeckia). Plant growth and flowering of both hibiscus and rudbeckia were influenced by concentration and ratio of N, P, and K. When N was held constant at 100 mg·L−1, 4:1 N:K (25 mg·L−1 K) and 16:1 N:P (6.3 mg·L−1 P) were optimal for growing hibiscus, whereas higher K concentration (1:2 N:K, 200 mg·L−1 K) and lower P concentration (32:1 N:P, 3.1 mg·L−1 N) were required for optimal growth of rudbeckia. However, when holding N constant at 100 mg·L−1 and varying both P and K in the fertilizer solutions, higher P and K concentrations and a 2:1:2 (50 mg·L−1 P, 100 mg·L−1 K) N:P:K ratio best supported hibiscus growth, whereas 3:1:2 (33 mg·L−1 P, 66 mg·L−1 K) N:P:K was needed for growth of rudbeckia. Finally, when both N concentration and N:P:K ratio were altered, optimum growth of both hibiscus and rudbeckia was achieved at similar and lower P and K concentrations (25 mg·L−1 P and 50 mg·L−1 K) and 200 mg·L−1 N. An 8:1:2 N:P:K ratio was optimum for production of both hibiscus and rudbeckia, although 12:1:2 N:P:K (200 mg·L−1 N, 17 mg·L−1 P, 33 mg·L−1 K) produced similar growth of rudbeckia. Based on results of these two herbaceous perennials, it appears herbaceous perennials have N requirements similar to annual plants and P and K requirements similar to woody plants. Furthermore, the two herbaceous perennials used in this study required nutrients in the fertilizer solution at a higher N:P:K ratio than either annual or woody plants. Foliar concentrations of 2.2% N, 0.4% P, and 1.9% K were adequate for growth of hibiscus, whereas 2.4% N, 0.2% P, and 2.6% K were required to maximize growth of rudbeckia.
Inheritance of Resistance in Melon PI 313970 to Cucurbit Powdery Mildew Incited by Podosphaera xanthii Race S
Authors: McCreight James D. , Coffey Michael D.
Published: February 2019

A new strain of cucurbit powdery mildew incited by Podosphaera xanthii (Castagne) Braun & Shishkoff (formerly Sphaerotheca fuliginea), designated race S, is virulent on all the commonly used melon (Cucumis melo L.) powdery mildew race differentials and first appeared on melon in Yuma, AZ, and Imperial Valley, CA, in 2003. Melon PI 313970 (C. melo var. acidulus) was resistant to P. xanthii race S in 2003 and subsequent years. Inheritance of resistance to P. xanthii race S was studied in two naturally infected, replicated field tests in Imperial Valley in 2005 and 2009 using the parents and F1, F2, and reciprocal backcross generations from crosses of PI 313970 with powdery mildew-susceptible ‘Top Mark’. Resistance to race S was recessive: all F1 and BCTM individuals were susceptible. One recessive gene, designated pm-S, conditioned resistance to race S in the F2 and BCPI. The relationship of pm-S to the previously reported recessive and codominant genes in PI 313970 for resistance to P. xanthii races 1, 2, 2U.S., 3, 3.5, 4.5, and 5 remains to be determined.
Rootstocks Affect Tree Growth, Yield, and Juice Quality of ‘Marsh’ Grapefruit
Authors: Castle William S. , Bowman Kim D. , Baldwin James C. , Grosser Jude W. , Gmitter Frederick G.
Published: February 2019

Two adjacent rootstock trials were conducted in the east coast Indian River region of Florida with ‘Marsh’ grapefruit (Citrus paradisi Macf.) scion. The objective was to find rootstocks to replace sour orange (C. aurantium L.) because of losses to citrus tristeza virus, and to replace Swingle citrumelo [C. paradisi × Poncirus trifoliata (L.) Raf.] because of its limited usefulness in certain poorly drained coastal sites. The trials were conducted in randomized complete blocks with 12 single-tree replicates spaced 4.6 × 6.9 m. The soils were of the Wabasso and Riviera series. The first trial consisted largely of trees on citrange [C. sinensis (L.) Osb. × P. trifoliata] and citrumelo rootstocks, ‘Cipo’ sweet orange (C. sinensis), and various hybrid rootstocks. The second trial involved mandarin rootstocks (C. reticulata Blanco) and sour orange and related rootstocks. Trees were grown for 7 years and yield and juice quality data were collected for the last 4 years of that period. Those rootstocks identified as the most promising, based on combinations of smaller tree size and high productivity and juice quality, were two Sunki mandarin × Swingle trifoliate orange (TF) hybrids (C-54, C-146), a Sunki mandarin × Flying Dragon TF hybrid, C-35 citrange, and a Cleopatra mandarin × Rubidoux TF hybrid (×639). The trees on these five rootstocks cropped well leading to soluble solids (SS) values of 3000 to 4000 kg/ha when they were 7-years old. The trees on C-54 and C-146 were relatively large, somewhat taller than trees on sour orange, whereas those on C-35 and the Sunki × Flying Dragon hybrid were smaller and similar to sour orange in tree height. Fruit quality among the trees on C-35 and the Sunki × Flying Dragon hybrid had relatively high SS concentration (better than sour orange), and the other three rootstocks had relatively lower solids concentration (poorer than sour orange). The trees on C-35 and the Sunki × Flying Dragon hybrid would be good candidates for higher density orchards.
Influence of Plant Bioregulators on Pecan Flowering and Implications for Regulation of Pistillate Flower Initiation
Authors: Wood Bruce W.
Published: February 2019

Mitigation of alternate bearing (AB) through regulation of floral initiation of pistillate flowers is central to improving cropload management of pecan [Carya illinoinensis (Wangenh.) K. Koch] trees and orchards. The present study examines the influence of key bioregulators {i.e., an auxin [as B-napththaleneacetic acid (NAA)], a cytokinin [6-benylamino purine (6-BA)], an ethylene generator (ethephon), and an auxin transport inhibitor [2,3,5-triiodobenzoic acid (TIBA)]} on subsequent season pistillate flowering. Gibberellic acid (i.e., GA3) and NAA inhibited, whereas prohexadione–calcium (P-Ca; calcium 3-oxido-5-oxo-4-propionylcyclohex-3-enecarboxylate), ethephon, and BA + TIBA promoted floral initiation when topically applied to canopies before the kernel filling stage of seed development. These bioregulators exhibit potential for integration into a bioregulator-based strategy to mitigate pecan AB by selective and timely use in “off” or “on” cycle years, depending on the bioregulator. Field studies provide evidence that a “cytokinin–gibberellin balance,” with partial modulation by auxin and ethylene, acts in the endogenous primordial environment of floral meristems as a “second-level signal” regulating a key step in a three-step process for initiation of pistillate flowers in pecan. This establishes a new model for explaining pistillate flower initiation in pecan and a basis for designing future research on the control and management of pistillate flowering and AB.