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Tim J. O’Hare, Hung Hong Trieu, Bruce Topp, Dougal Russell, Sharon Pun, Caterina Torrisi and Dianna Liu

The kernel of the macadamia nut (Macadamia integrifolia and M. tetraphylla) is very high in oil, accounting for about three -quarters of their mass. In the current investigation, oil extracts from 20 breeding accessions and 14 cultivars had a range of 12.3% to 17.0% saturated fat, averaging 14.2%. Although all samples were found to be very high in “healthy” monounsaturated fats, the level of saturated fat slightly exceeds that of many other nuts that are able to make qualified health claims. The lowest saturated fat content (12.3%) corresponded to 4.6 g saturated fat/50 g kernels, which was slightly greater than the 4.0 g maximum. Despite this, potential exists to develop a reduced-saturated fat macadamia by combining characteristics found in different lines. The current trial indicates that lower total saturated fat was associated with a stronger ability to partition C16 and C18 fats to their monounsaturated fatty acids, or to elongate C16:0 to C18:0 and subsequently desaturate C18:0 to C18:1. It was also observed that the pollinizer parent is likely to have an influence on saturated fat content, although this would need to be confirmed in controlled pollination trials. Macadamia varieties generally outcross, and because the edible kernel (embryo) is formed from a pollinated ovule, it is likely any future reduced-saturated fat line would also require a reduced-saturated fat pollinizer parent.

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Craig Hardner, João Costa e Silva, Emlyn Williams, Noel Meyers and Cameron McConchie

In 2017, five new cultivars specifically selected for Australian conditions were released. These were developed from an improvement program initiated by Commonwealth Scientific and Industrial Research Organisation in the early 1990s. Progeny seeds were produced by crossing industry standard cultivars with other cultivars with elite kernel production per unit projected canopy area. Seedlings were planted at two densities (2 m and 4 m along rows) in field trials at Bundaberg in 1997 and 1998, and Northern New South Wales in late 1997, along with replicated plants of parents grafted onto seedling rootstocks. Trials were assessed for commencement of flowering, growth, yield, kernel recovery, and components of kernel quality over 8 years. Best linear unbiased predictions of clonal values were obtained for each individual progeny using a pedigree-based mixed linear model. A bio-economic model was used to estimate economic weights for a selection index of clonal values to identify elite candidates. Final approval of 20 candidates for second-stage assessment was made by an industry committee using selection index rankings and observations of tree field performance and kernel quality.

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Valdinar Ferreira Melo, Edvan Alves Chagas, Raphael Henrique da Silva Siqueira, Olisson Mesquita de Souza, Luís Felipe Paes de Almeida, Diogo Francisco Rossoni, Pollyana Cardoso Chagas and Carlos Abanto-Rodríguez

Camu-camu is an native species in domestication processes. Therefore, studies related to the root system are necessary to evaluate the best cultivation practices for an orchard. Two trials were conducted, one with nitrogen (N) and the other with potassium (K), at doses of 0, 40, 80, 160, and 320 kg·ha–1. Root distribution was determined using nondestructive analyses in which two-dimensional (2D) root images were obtained from trenches under the plants’ canopy. Variables included width (measured in cubic millimeters), area (measured in square millimeters), and length (measured in millimeters, and were analyzed using Safira software (version 2010, Embrapa, Brazil). To have better spatial visualization of variable distribution in the soil profile, data were analyzed using the ordinary kriging technique with the geoR software package and R software (version 2016). Both N and K doses influenced positively the camu-camu root system with regard to length, volume, and area. Better root distribution was verified with 80 kg·ha−1 N and 160 kg·ha−1 K doses. The nondestructive analysis via 2D images allowed sound characterization of root spatial distribution.

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W. Garrett Owen and Roberto G. Lopez

Variability in outdoor daily temperatures and photosynthetic daily light integrals (DLIs) from early spring to late fall limits the ability of propagators to accurately control propagation environments to consistently callus, root, and yield compact herbaceous perennial rooted liners. We evaluated and compared the effects of sole-source lighting (SSL) delivered from red (R) and blue (B) light-emitting diodes (LEDs) to supplemental lighting (SL) provided by high-pressure sodium (HPS) lamps on herbaceous perennial cutting morphology, physiology, and growth during callusing and initial rhizogenesis. Cuttings of perennial sage (Salvia nemorosa L. ‘Lyrical Blues’) and wand flower (Gaura lindheimeri Engelm. and A. Gray ‘Siskiyou Pink’) were propagated in a walk-in growth chamber under multilayer SSL provided by LEDs with [R (660 nm)]:[B (460 nm)] light ratios (%) of 100:0 (R100:B0), 75:25 (R75:B25), 50:50 (R50:B50), or 0:100 (R0:B100) delivering 60 µmol·m−2·s–1 for 16 hours (total DLI of 3.4 mol·m−2·d−1). In a glass-glazed greenhouse (GH control), cuttings were propagated under ambient solar light and day-extension SL provided by HPS lamps delivering 40 µmol·m−2·s–1 to provide a 16-hour photoperiod (total DLI of 3.3 mol·m−2·d−1). At 10 days after sticking cuttings, callus diameter and rooting percentage were similar among all light-quality treatments. For instance, callus diameter, a measure of growth, of wand flower cuttings increased from an average 1.7 mm at stick (0 day) to a range of 2.7 to 2.9 mm at 10 days after sticking, regardless of lighting treatment. Relative leaf chlorophyll content was generally greater under SSL R75:B25 or R50:B50 than all other light-quality treatments. However, stem length of perennial sage and wand flower cuttings propagated under SSL R50:B50 at 10 days were 21% and 30% shorter and resulted in 50% and 8% greater root biomass, respectively, compared with those under SL. The herbaceous perennial cuttings propagated in this study under SSL R50:B50 were of similar quality or more compact compared with those under SL, indicating that callus induction and initial rooting can occur under LEDs in a multilayer SSL propagation system.

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Jen A. Sembera, Tina M. Waliczek and Erica J. Meier

Wild taro (Colocasia esculenta) is identified as an invasive species in freshwater regions throughout the southeastern United States as well as Puerto Rico, Jamaica, and India, and thrives in freshwater swamps, streambanks, and riparian areas with rocky crevices that provide strong footholds. Management methods for the plant include using herbicides, mechanical cutting, manual removal, or a combination of methods with disposal into landfills. The purpose of this study was to evaluate the potential to manage wild taro waste using composting and to test the quality of the resulting compost. This study used ≈12 yard3 of wild taro mixed with food waste and regionally harvested wood chips to create ≈6 yard3 of cured compost. Oven propagule mortality tests determined wild taro propagules exposed to temperatures between 45 and 52 °C for a minimum of 3 days were killed. These temperatures were achieved during the active phase of the composting process. The final compost products created were of equal or higher quality to current compost standards. Therefore, this study determined composting and waste management industries can accept and incorporate wild taro as a feedstock to create a desirable compost product for application in the horticulture and agriculture fields rather than managing the species with herbicides and/or other disposal methods.

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Julie H. Campbell and Benjamin L. Campbell

A survey of Connecticut consumers was used to investigate perceptions of various green industry retailers. Consumer perceptions of independent garden centers (IGC), home improvement centers (HIC), and mass merchandisers (MM) business practices and their perceived value were assessed. Analysis of variance and ordinary least squares regression models were used to analyze the data. Results indicated that customer service, knowledgeable staff, and high-quality plants are important factors when consumers are deciding where to shop. IGCs were ranked highest in perceived customer service, knowledgeable staff, and plant quality, followed by HICs. MMs were ranked lowest for the majority of measured business practices, with the most notable exception being price. Additionally, IGCs, HICs, and MMs are perceived differently across age cohorts.

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Douglas G. Bielenberg and Ksenija Gasic

Inexpensive plug-and-play temperature controllers have recently become available. These allow a chest freezer to be programmed easily to hold a desired set point across a range of biologically relevant temperatures. Installation can be completed in a few minutes using consumer-grade chest freezers. We used these temperature controllers to create five temperature-controlled chambers at 12, 14, 16, 18, and 20 °C. We demonstrated the use of these controlled-temperature chambers with two biologic assays: floral budbreak of peach [Prunus persica (L.) Batsch] stem cuttings and germination of sunflower (Helianthus annuus L.) seeds. We used the budbreak and germination rates at multiple temperatures to estimate base temperatures and thermal time requirements for development.

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S. Kaan Kurtural, Andrew E. Beebe, Johann Martínez-Lüscher, Shijian Zhuang, Karl T. Lund, Glenn McGourty and Larry J. Bettiga

A field study was conducted for three consecutive seasons in the hot climate of central California to assess the performance of ‘Merlot’ grapevine (Vitis vinifera) grafted onto ‘Freedom’ [Fresno 1613-59 × Dog Ridge 5 (27% V. vinifera hybrid)] during training system conversion to facilitate mechanization. The traditional head-trained and cane-pruned (CP) system was either retained or converted either to a bilateral cordon-trained, spur-pruned California sprawl training system (HP), or to a bilateral cordon-trained, mechanically box-pruned single high-wire sprawling system (SHMP). After the conversion, SHMP sustained greater yield with more clusters per vine and smaller berries without affecting the canopy microclimate. This was due to a higher number of nodes retained after dormant pruning. The SHMP canopies, compared with CP and HP; filled allotted canopy space earlier based on photosynthetically active radiation (PAR) transmitted through the canopies, populating the space allotted per vine, favoring higher production efficiency. There were no adverse effects of training systems on berry composition or flavonoid concentration, during or after conversion to mechanical management. However, experimental year effect was obvious on anthocyanin composition of ‘Merlot’ berries, increasing trihydroxylated (i.e., delphinidin-based) anthocyanins in the latter years of the experiment. Our results also provided evidence that earlier canopy growth coupled with sufficient reproductive compensating responses allowed for increased yields while reaching commercial maturity without a decline in anthocyanin content with the SHMP. Converting CP to SHMP reduced labor operations costs by 90%. Furthermore, the SHMP had greater gross revenue and resulted in greater net income per acre even when the conversion year was taken into account. Therefore, SHMP is recommended for growers within the hot climate of the central San Joaquin Valley as a means to maintain productivity of vineyards while not sacrificing berry composition at the farm gate.

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Brad G. Howlett, Samantha F.J. Read, Maryam Alavi, Brian T. Cutting, Warrick R. Nelson, Robert M. Goodwin, Sarah Cross, Trevor G. Thorp and David E. Pattemore

Macadamia is partially self-incompatible and cross-pollination is considered important to improve yields. However, questions remain regarding the importance of self- vs. cross-pollination, and subsequently whether managed pollinators are useful in commercial orchards. Pollinators play a key role in cross-pollination, but for self-pollination, the protandrous florets might also benefit from the movement of potentially more viable self-pollen among florets, racemes, and trees through pollinator movement. There is also a lack of information on pollination deficits throughout orchards and whether by increasing the intensity of cross-pollination, final nut yield is limited by within-tree resource allocation. Using caged and bagged racemes on three cultivars, we found strong evidence for self-pollination, but no evidence that hand moving self-pollen within racemes, between racemes, or between trees improved final nut set. In all cases, hand cross-pollinated racemes yielded significantly more nuts. Hand cross-pollinated racemes also produced significantly more developed nuts than open-pollinated racemes (all racemes were exposed to pollinators). However, by increasing the intensity of hand cross-pollination per tree, we showed that resource allocation probably overinflates these measures of pollination deficit in macadamia. Despite this, our findings point to an opportunity to increase yields through additional cross-pollination, as high-intensity hand cross-pollination of flowering racemes within trees still resulted in increased nut set. Although self-pollination can occur in macadamia, to optimize yield potential, strategies to maximize cross-pollination should be adopted.

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Jun Liu, Orville M. Lindstrom and Dario J. Chavez

Differential thermal analysis (DTA) has great potential as a quick and convenient cold hardiness determination method in plants. It measures freezing events inside of plant samples by detecting exotherm(s) produced when water changes from liquid to solid phase. DTA is highly sensitive to the experimental conditions and it has been reported to be ineffective among different fruit crops after acclimation of floral buds has occurred. The objective of this project was to establish DTA as a rapid and accurate method to predict peach floral bud cold hardiness from acclimation to deacclimation as compared with the traditional standard artificial freezing test. Floral buds of ‘Elberta’ and ‘Flavorich’ peach cultivars were subjected to DTA and artificial freezing tests throughout the winters of 2015–16 and 2016–17. Before deacclimation, two distinct exotherms, low-temperature exotherms (LTE) and high-temperature exotherms (HTE), were normally detected from floral bud DTA analyses. After deacclimation, DTA tests yielded only a few LTEs. However, incubation of floral buds at −2 °C overnight before the cooling process of DTA tests yielded an increased number of LTEs for both seasons in comparison with samples directly run using DTA without incubation. Similarly, after deacclimation started, the temperature in which LTE occurred was correlated (r = 0.59–0.86) with LT50 (lethal temperature that damaged 50% of floral buds) when DTA samples were treated overnight at −2 °C. In our study, pretreatment of floral buds at −2 °C overcame the inability of DTA to detect LTEs after deacclimation, which improved the ability and reliability of DTA to detect LTEs for more than 50% of the buds used per date per cultivar. DTA is a promising method to predict cold hardiness of peach plants.