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Open access

Koichi Nomura, Masahiko Saito, Ikunao Tada, Tadashige Iwao, Tomihiro Yamazaki, Nobuyuki Kira, Yasuyo Nishimura, Makito Mori, Esteban Baeza, and Masaharu Kitano

In horticultural greenhouses, the photosynthetic photon flux density (I) is inevitably lower than that outside because of interference from greenhouse superstructures (e.g., reflection and absorption of radiation by greenhouse coverings and superstructures). In addition, during hot seasons in many regions, I can be lowered by shade nets installed to reduce excessive radiation. These reductions in I can cause a decrease in the canopy photosynthetic rate (A c), potentially leading to crop yield losses. This study investigated to what extent A c is reduced inside a modern greenhouse and under a shade net in comparison with that outside. A simple A c model (i.e., canopy-scale photosynthesis-light curves) was parameterized based on the measurements of A c and I for paprika and tomato canopies using the open-chamber method. In addition, based on the measurements of I, linear regression models were derived that related outside I (I out) with I inside arch-roofed, single-span greenhouses [enveloped with a diffuse ethylene tetrafluoroethylene (ETFE) film; I in] and I under shade nets (composed of aluminum and polyester strips; I sh). An A c simulation using these models indicated that on a typical sunny summer day in Japan, A c inside the greenhouses and under the shade nets (A c,in and A c,sh, respectively) corresponded to 91% and 52% of A c outside (A c,out) for the paprika canopy (for the tomato canopy, A c,in and A c,sh corresponded to 90% and 48% of A c,out, respectively). The simulated A c loss was more serious on a cloudy day because of the linear A c-I response under low I conditions (A c,in/A c,out and A c,sh/A c,out were 69% and 13%, respectively, for the paprika canopy). The loss of A c,sh may be alleviated by limiting the shading period to only midday hours.

Open access

Kristopher S. Criscione, Jeb S. Fields, Jim S. Owen Jr., Lisa Fultz, and Edward Bush

Growers rely on soilless substrates to provide sufficient water and nutrients to containerized crops. Traditional bark-based substrates are engineered to have relatively low water-holding capabilities, which can lead to nonuniform rewetting patterns and inefficient usage of water resources. Engineering substrates to redistribute water dynamics and maximize aeration within the container may improve water resource efficiencies. The goal of this study was to evaluate whether more efficient irrigation schedules can be used when stratifying unique substrates within a container for added crop water and nutrient efficiency. Loropetalum chinense ‘Ruby’ liners were planted and grown in a conventional pine bark substrate or one of three stratified substrate treatments, including a bark:peat, bark:coir, or fine bark layered on top of a coarse bark. The crops were grown under four different irrigation schedules, including single daily application, single application at deficit levels, cyclic application, or cyclic at deficit schedules. Stratified substrates improved crop growth, quality, and yield when compared with plants grown in conventional bark in the single application irrigation treatment. Measured at final harvest, substrates positively influenced plant growth index (P < 0.0001), whereas irrigation scheduling alone had no effect (P = 0.6321). There was a strong interaction between substrate and irrigation schedules on Δ growth index (P = 0.0141). There were strong substrate effects on shoot dry weight (P = 0.0060), root dry weight (P = 0.0342), and growth index (P = 0.0040). The stratified bark:coir treatment outgrew all other substrate treatments. In addition, within all irrigation treatments, plants grown with the stratified bark:coir substrate had the highest survival ratings among the other substrate treatments, whereas the conventional bark had the lowest survival rates. Substrate and irrigation had an effect on nitrogen and potassium leachate concentrations levels (P = 0.0107 and P = 0.0004, respectively). Evaluation of microbial communities showed that substrate (P = 0.0010) and the stratified layer (P = 0.0010) had strong influences on the type of community present and the relative abundance in the treatments used herein this study. Specifically, within cyclic scheduling, bark:peat actinomycete populations were significantly greater than other substrate treatments. Furthermore, under deficit irrigation, stratified substrate systems were able to mitigate crop water stress. The results indicate that when crops such as the Loropetalum are grown in the stratified system, crop growth can be sustained when drought conditions are present. This is possible by providing adequate water availability even under low water inputs until subsequent irrigations during the fragile establishment period, when compared with using traditional bark-based substrates.

Open access

James J. Luby, Nicholas P. Howard, John R. Tillman, and David S. Bedford

Apple (Malus ×domestica Borkh.) breeding at the University of Minnesota (UMN) has been ongoing continuously since 1908 when staff originally planted thousands of seedlings from open-pollinated (OP) seeds collected from regional orchards. The first cultivar from the program, ‘Minnehaha’, was introduced in 1920 and several others from these OP seeds followed over the next 3 decades. Controlled crosses were initiated in 1916, and until the time of this publication, 28 cultivars have been introduced. Historical records of parentage, as recorded by staff in notebooks and in 20th-century publications, have been used to inform breeding decisions but might be incorrect as indicated by earlier explorations of parentage using simple sequence repeat (SSR) markers. Our objective was to elucidate parentage and extended pedigrees of all available cultivars introduced from the UMN apple breeding program using evaluations of Mendelian errors and shared haplotype length information based on data from single nucleotide polymorphism (SNP) arrays. Sixteen of the 21 cultivars introduced before ‘Honeycrisp’ (1991) had incorrect or incomplete pedigrees that are now at least partially elucidated. These include the two most important regional cultivars in the 20th century: ‘Haralson’ (parents: ‘Malinda’ and ‘Wealthy’) and ‘Fireside’ (parents: ‘Wealthy’ and ‘Northwest Greening’). ‘Wealthy’, a widely grown cultivar in the United States in the late 19th and early 20th centuries, was a frequent parent of older UMN cultivars. ‘Malinda’ was a less frequent parent than indicated by breeding records. ‘Duchess of Oldenburg’ (synonym ‘Borowitsky’) was revealed as an ancestor of overwhelming importance in the UMN breeding program. It was an ancestor of 27 of the 28 UMN cultivars, including as a parent of two cultivars, and a grandparent of 15 cultivars, including ‘Honeycrisp’.

Open access

Hongli Wei, Chao Gao, Jie Qiu, Zhiyan Guo, Biao Wang, and Li Long

Camellia weiningensis is a typical woody edible oil tree species in the northwest alpine area of Guizhou Province, China, but its embryological development is not fully elucidated. Here, we assessed flower bud differentiation, microsporogenesis, and male-female gametophyte development in this species. We performed cytological observations of flower bud development in C. weiningensis through conventional paraffin sectioning, scanning electron microscopy, and stereomicroscopy to establish the corresponding relationships between the external morphology and internal structure. The flowers were hermaphroditic and exhibited a short flower bud differentiation time. Although pistil development occurred later than stamen development, both organs matured synchronously before flowering. The anther contained four sacs that exhibited a butterfly shape in transverse sections. The anther wall comprised the epidermis, anther chamber inner wall, two middle layers, and a glandular tapetum (from outside to inside). Microspore mother cells formed a tetrahedral tetrad through meiosis, mature pollen was two-celled with three germination pores, and the ovary comprised three to five chambers (three chambers predominated). Multiple ovules were invertedly attached to the axial placentation and exhibited double integuments and a thin nucellus. The embryo sac exhibited Allium-type development, and the mature embryo sac was seven-celled and eight-nucleated. In C. weiningensis, embryonic development does not exhibit abnormalities, and stamen development occurs earlier than pistil development. During flower bud development, the inner development process of male and female cells can be judged according to their external morphological characteristics. Our results may provide a theoretical basis for regulating flowering in and the cross-breeding of C. weiningensis.

Open access

Thomas E. Marler

Conservation of the endangered Serianthes nelsonii is constrained by lack of research. Transplanted containerized plants die in the competitive in situ environment. This study determined if foliar applications of nutrient solution could replace edaphic fertilizer applications for mitigating competition for soil nutrients. Weekly sprays with 0.1× Hoagland solution were compared with weekly drenches of 0.5× Hoagland solution. Plants receiving edaphic or foliar nutrition were not different in height, and height growth was 72% above that of control plants. Similar results were obtained for stem diameter and leaf number. Leaf nutrient concentrations were not different for the two nutrition treatments, but stem nutrient concentration differences were dependent on the element. Stem copper, nitrogen, phosphorus, potassium, and zinc concentrations were not different for edaphic vs. foliar nutrition. Contrarily, stem boron, calcium, iron, magnesium, and manganese concentrations were greater in plants receiving edaphic nutrients. The results indicate nutritional needs of recently out-planted plants may be supplied directly to leaves to mitigate below-ground competition for nutrient resources.

Open access

Matthew S. Lobdell and Kimberly Shearer

Styrax L. is a genus of ≈130 species, many with horticultural traits of interest, though sparsely represented in cultivation. Previous studies reporting chromosome counts have established a base chromosome number of x = 8 and provided evidence of diploid, tetraploid, pentaploid, and hexaploid levels within the genus, including the more commonly cultivated Styrax japonicus Siebold & Zucc. being reported as pentaploid. Little has been reported relative to genome size within the Styracaceae. We conducted flow cytometry using fluorochromes propidium iodide (PI) and 4′,6-diamidino-2-phenylindole (DAPI) to estimate relative 2C genome size and ploidy of 47 accessions representing 15 species of Styrax and base composition of a subset of 9 accessions representing 6 species. Cytologic analysis of chromosomes was completed on Styrax confusus Hemsl. for ploidy calibration to genome size. Diploids, tetraploids, pentaploids, hexaploids, and octoploids were identified. Relative 2C genome size ranged from 1.38 to 6.61 pg. This survey confirms published ploidy for Styrax americanus Lam., Styrax obassia Siebold & Zucc., Styrax redivivus (Torr.) L.C.Wheeler (diploid), and S. japonicus (pentaploid); suggests alternate ploidy levels and/or ploidy series for Styrax grandifolius Aiton (diploid) and Styrax hookeri C.B.Clarke (octoploid); and establishes ploidy levels for Styrax glabrescens Benth., Styrax odoratissimus Champ. ex Benth., Styrax officinalis L., Styrax platanifolius Engelm. ex Torr., Styrax ramirezii Greenm., Styrax wilsonii Rehder (diploid), Styrax confusus, Styrax hemsleyanus Diels (tetraploid), and Styrax fortunei Hance (diploid and hexaploid).

Open access

Steven C. Haring, Junjun Ou, Kassim Al-Khatib, and Bradley D. Hanson

Grape growers are concerned about the potential impact of drift from commonly used auxinic herbicides. In California, this is frequently related to herbicides used in cereals and noncrop areas, whereas in other parts of the United States concerns are often related to dicamba- and 2,4-D-resistant cropping systems. Our objective was to compare the relative sensitivity of winegrapes to simulated auxinic herbicide drift, including grapevine symptomology, grape yield, and grape quality. In a small-plot herbicide evaluation, we applied 1/900×, 1/300×, 1/100×, and 1/33× rates of 2,4-D, aminopyralid, dicamba, and triclopyr based on 1× field rates of 1454, 122.5, 280, and 2240 g⋅ha–1 ae, respectively. Aminopyralid resulted in similar symptomology to 2,4-D and dicamba—namely, leaf cupping, leaf crinkling, excessive tendril twisting, and tendril death, although these symptoms were generally subtle. Triclopyr resulted in much greater levels of necrosis compared with the other herbicides. In our study, triclopyr was the only herbicide associated with grape yield loss, and greater triclopyr rates were also associated with increased grape sugar levels. This study demonstrates that grapes are sensitive to low rates of simulated herbicide drift, but symptoms do not necessarily indicate yield loss or quality effects. This study indicates that auxin-type herbicide simulated drift symptoms are not reliable markers for winegrape yield or quality reduction.

Open access

Renee T. Threlfall, John R. Clark, James N. Moore, and Justin R. Morris

‘Indulgence’ and ‘Dazzle’ wine grapes are new cultivars (Vitis hybrid) developed by the University of Arkansas System Division of Agriculture (UA System). These grapes are the third and fourth wine grape cultivars from the program. These white wine grape cultivars have shown good adaptation and consistent productivity in Arkansas. Enological evaluations have shown that these cultivars produced high-quality wines from fruit grown in Arkansas. It is envisioned that these cultivars will be best used by Arkansas wine grape growers as well as those in the mid-South. Winemakers can use these cultivars to expand unique wine options for the