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Open access

Heidi C. Anderson, Mary A. Rogers and Emily E. Hoover

Consumer demand for local and organic strawberries (Fragaria ×ananassa) is increasing. Growers who can meet this demand have a competitive edge in the direct-to-consumer market. Innovations in strawberry production for northern climates offer new opportunities for growers to meet the demand for local organic strawberries. Typically adopted for season extension, the use of poly-covered tunnels for crop protection provides other benefits including protection from adverse weather. Low tunnels are easy to install, low cost, temporary protective structures that are well-adapted for annual day-neutral strawberry production, and they are more space efficient than high tunnels for these low-stature crops. A range of specialty tunnel plastics that modify and diffuse light are available, but there is little information on how these influence strawberry plant growth and performance in the field. Our objectives were to determine the effects of experimental ultraviolet blocking and transmitting plastics on light and microclimate in low tunnel environments and assess differences in fruit yield and quality in the day-neutral strawberry cultivar Albion in an organic production system. This research was conducted on U.S. Department of Agriculture-certified organic land over 2 years, in 2016 and 2017. We found that ultraviolet intensity and daily light integral (DLI) were lower in covered plots than in the open field. Maximum daily temperatures were slightly higher in covered plots. Both ultraviolet-blocking and ultraviolet-transmitting plastics improved marketable fruit yield compared with the open-field control. Strawberries grown in the open-field treatment were lower in chroma than covered plots in 2017, and there was no difference in total soluble solids between treatments in either year. Low tunnel systems allow for increased environmental control and improved fruit quality and are well-adapted for day-neutral organic strawberry production systems.

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Fengxia Shao, Sen Wang, Juan Chen and Rongyan Hong

To investigate whether reproductive disorders exist in the sexual reproduction of Ziziphus jujuba Mill. ‘Zhongqiusucui’ and to understand the reproductive biology of ‘Zhongqiusucui’ and genetic improvements in jujube trees, we used ‘Zhongqiusucui’ flowers at different developmental stages as materials and conducted field and microscopic observations on the developmental pattern of mega- and microsporogenesis, as well as on the development of male and female gametophytes. The results show the following. 1) From the inflorescence development stage to flowering, the grade 0 bud on the inflorescence exhibited an increase in horizontal diameter, longitudinal diameter, peduncle length, and bud weight, but the rates of increase were different. From day 1 to day 5 after the inflorescence had developed, floral buds mostly grew horizontally. Day 5 was the floral bud flattening stage. From day 6 to day 8 after the inflorescence had developed, floral buds mostly grew longitudinally, and day 8 was the floral bud enlarging stage. 2) The stamens of ‘Zhongqiusucui’ had five anthers, and there were four locules per anther. The anther wall consisted of epidermis, endothecium, one- to two-layered middle layer, and a secretory-type tapetum. In addition, the development of the anther wall belonged to the basic type. The cytokinesis of the microsporocytes was synchronous, the tetrads mostly arranged as a tetrahedron, and the mature pollen had three germ pores, three grooves, and was bicellular pollen. During meiosis, the microsporocytes in each locule were at the same phase and therefore exhibited synchrony. Among the different anthers in the same floral bud, as well as the four locules in the same anther, the microsporocytes had asynchronous meiosis. 3) The pistils in the ‘Zhongqiusucui’ had two ovaries, two anatropous ovules, inner and outer integument, crassinucellate tetrads formed by the meiosis of megasporocytes aligned linearly along the nucellus, megaspore at the chalazal end that developed into the functional megaspore, which underwent mitotic division three times and developed into the mature embryo sac containing seven cells and eight nuclei, and embryo sac development of the Polygonum type. 4) The external morphology of the ‘Zhongqiusucui’ floral buds correlated with the internal developmental stage of the male and female gametophyte. Therefore, the internal developmental progress of the stamen and pistil can be determined by the external morphological characteristics of the floral buds.

Open access

Michael A. Schnelle

Five woody species, black locust (Robinia pseudoacacia), yaupon holly (Ilex vomitoria), black cherry (Prunus serotina), snailvine [Cocculus carolinus (formerly Menispermum carolinum or Epibaterium carolinum)], and southern waxmyrtle [Morella cerifera (formerly Myrica cerifera)], are all native to Oklahoma and nearby states. They all have varying levels of use in and importance to the United States nursery industry. Past natural habitats and where these plants have spread to date, either intentionally or naturally, are discussed here. These native plants have migrated to or have become increasingly dominant in regions of the continental United States because of prolific fruit loads dispersed by birds and mammals, anthropogenic disturbances, overgrazing pastures, and certain species’ tolerance of environmental extremes. Potential control measures include chemical applications, timely cultivation, heightened awareness of grazing practices, and prescribed burning.

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Yang Chen, Xianzhi Zhou, Yongsheng Lin and Yucan Zhang

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Adriano dos Santos, Francisco Eduardo Torres, Erina Vitório Rodrigues, Ariane de Andréa Pantaleão, Larissa Pereira Ribeiro Teodoro, Leonardo Lopes Bhering and Paulo Eduardo Teodoro

This study aimed to evaluate the adaptability and phenotypic stability of cowpea genotypes using a nonlinear regression analysis and multivariate analysis. Experiments were performed at four sites in Brazil using a randomized blocks design with 20 treatments and four replications. The adaptability and stability of genotypes were evaluated by Toler nonlinear regression and genotype plus genotype × environment (GGE) biplot methodologies. Most of the genotypes revealed linear response patterns, with no differences regarding the favorable and unfavorable environments. Regarding the genotype classification for stability and adaptability, the Toler and GGE biplot methodologies are congruent. Genotypes MNC99-537F-4, MNC00-561G-6, MNC99542F-5, and Patativa have high overall adaptability and adequate yield. Therefore, they should be recommended for cultivation in the tested environments. Genotypes closer to the ideotype by the GGE biplot method are considered doubly desirable by the nonlinear method.

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Carlos Henrique Oliveira de David, Vespasiano Borges de Paiva Neto, Cid Naudi Silva Campos, Priscilla Maria da Silva Liber Lopes, Paulo Eduardo Teodoro and Renato de Mello Prado

This study evaluated the impact of macronutrient omission on nutritional disorders and the in vitro growth of Bletia catenulata. The experiment was performed in a growth room, with a controlled environment, in the biotechnology laboratory of the Campus of Chapadão do Sul (CPCS/UFMS). The experiment consisted of a completely randomized design, with seven treatments and four replications, corresponding to the following treatments: complete treatment (N, P, K, Ca, Mg, S, B, Mn, Zn, Cu, Fe, and Mo), nitrogen omission (–N), phosphorus omission (–P), potassium omission (–K), calcium omission (–Ca), magnesium omission (–Mg), and sulfur omission (–S) in B. catenulata. After detecting the symptoms, plant height, leaf area, dry weight, micronutrient content in the shoot, micronutrient accumulation in the shoot, and visual symptoms of nutritional deficiency were evaluated. The –N, –P, –Ca, and –Mg treatments hindered plant growth and dry weight yield. The deficiency of each nutrient resulted in morphological changes, which were verified by typical visual symptoms of nutritional disorder for each nutrient.

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Bernadine C. Strik, Amanda Vance, David R. Bryla and Dan M. Sullivan

The impact of various production systems on leaf nutrient concentration and soil organic matter, pH, and nutrient status was evaluated from the first growing season (2007) through maturity (2016) in a certified organic planting of northern highbush blueberry (Vaccinium corymbosum L.). Treatments included planting method (on raised beds or flat ground), fertilizer source (granular feather meal or fish solubles) and rate (“low” and “high” rates of 29 and 57 kg·ha−1 N, respectively, during establishment, increased incrementally as the planting matured to 73 and 140 kg·ha−1 N, respectively), mulch [sawdust, yard-debris compost topped with sawdust (compost + sawdust), or black, woven polyethylene groundcover (weed mat)], and cultivar (Duke or Liberty). Mulches were replenished, as needed, and weeds were controlled throughout the study. The impacts of year, planting method, fertilizer, mulch, and cultivar on leaf and soil nutrient levels over this 10-year study were complex with many interactions among treatments. Soil pH remained within the recommended range for all treatments. Plants fertilized with fish solubles had higher leaf N, P, and K concentrations than those fertilized with feather meal, particularly at the high N rate in both cultivars. By contrast, fertilization with feather meal increased leaf Ca. Compost + sawdust added a cumulative (2007–16) total of 2274, 400, 961, and 2744 kg·ha−1 of N, P, K, and Ca, respectively, over the use of sawdust alone, and increased the concentration of P, K (as much as 90%), Ca, and Mg in the soil relative to other mulches. Soil organic matter content averaged 4.1% under compost + sawdust, 3.3% under sawdust, and 2.9% under weed mat, averaged over the last 5 years. Mulching with weed mat or compost + sawdust increased leaf K compared with sawdust in both cultivars, regardless of fertilizer treatment. Leaf Ca, on the other hand, was highest with sawdust and tended to be lowest with weed mat in both cultivars. Soil nutrient levels were not consistently correlated with leaf nutrient concentrations, other than between soil NO3-N and leaf N (5 years) and between soil and leaf K (4 years). On average, raised beds resulted in higher concentrations of N, P, K, Fe, and Al and lower concentrations of Ca, Mg, and B in the leaves than planting on flat ground. Furthermore, concentrations of N and Ca in recent fully-expanded leaves at standard sampling time was higher in young plants than in mature plants in both cultivars, whereas the opposite was found for leaf P. In ‘Duke’, yield was positively correlated with leaf Ca in 8 out of 9 years and negatively correlated with leaf K and P in 5 and 6 years, respectively. Leaf Ca and Mg were also negatively correlated with leaf K in most years for both cultivars, as was leaf N. Although leaf N concentration was higher with added compost, regardless of fertilizer source in ‘Duke’, and when fertilized with feather meal in ‘Liberty’, this was not correlated with yield. High N rates increased leaf N concentration, but did not result in greater yield. While soil and leaf tissue testing are important to help manage fertilizer programs, the lack of a consistent relationship between soil and plant nutrient status and yield was a reflection of the complicated interactions that occurred among nutrients in these organic production systems. Soil nutrient imbalances and changes in leaf nutrient concentrations associated with extended use of compost + sawdust mulch and fish solubles may lead to growth and yield problems in longer-lived plantings. In addition, the loss of organic matter under weed mat would need to be addressed in long-term plantings for sustainable production.

Open access

Wenjing Guan, Elizabeth T. Maynard, Bronwyn Aly, Julie Zakes, Daniel S. Egel and Laura L. Ingwell

Fresh-consumed parthenocarpic cucumbers (Cucumis sativus) are a popular and high-value crop sold in local food markets. The parthenocarpic plant characteristics and climbing growth habit make cucumbers an ideal crop for high-tunnel production. Major types of parthenocarpic cucumbers include Beit alpha and mini, Dutch greenhouse, American slicer, and Japanese. Information regarding yield performance, plant growth, and disease resistance of the four types grown in high-tunnel conditions is limited. In this study, 16 parthenocarpic cucumber cultivars from the four major types were evaluated in high tunnels at three locations in Indiana and Illinois during Spring 2018. Plants were pruned to a single stem that was supported on a string. At all locations, the cultivars that had the most total yields were Beit alpha and mini, although their total yields were not always significantly higher than that of all the others. However, Beit alpha and mini cucumbers had high percentages of unmarketable fruit, mainly because of insect feeding damage and mechanical injuries on the skins that led to scarred fruit. Dutch greenhouse cultivars had relatively lower marketable yields at two of the three locations where there was a high percentage of misshaped fruit. ‘Tasty Green’ Japanese cucumber consistently had the lowest yields at all three locations. This cultivar also produced the most side shoot growth and, therefore, more pruning waste. The Japanese types ‘Tasty Jade’ and ‘Taurus’ had yields comparable to those of other cultivars, and they were more tolerant to two-spotted spider mites (Tetranychus urticae). However, ‘Tasty Jade’ was the cultivar most susceptible to powdery mildew (Podosphaera xanthii and Golovinomyces cichoracearum). ‘Corinto’ American slicer cucumber had relatively high yields at two of the three locations. This cultivar also had the highest percentage of marketable fruit. Information provided in the study is readily useful for growers using high tunnels when selecting parthenocarpic cucumber cultivars. It is also valuable for seed companies wishing to breed new cultivars adaptive for high-tunnel production.

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John Erwin, Tanveer Hussein and David J. Baumler

The instantaneous photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (g S) were measured for 33 outdoor-grown Capsicum varieties (varying in species of origin and indigenous habitat) between 29 July and 22 Aug. 2017 using a portable gas exchange meter. Cuvette leaf temperature (Tleaf) and relative humidity (RH) were recorded at that same time. Pn differed from 3.6 to 3.7 for ‘Malawi Piquante’ and ‘Korean Long Green’ peppers to 16.3 μmol CO2/m2/s (fixed) for ‘Thai Hot’ peppers. The g S differed from 0.01 to 0.05 among 13 varieties to 0.28 mmol H2O/m2/s for ‘Thai Hot’ peppers. E differed from 0.43 to 0.59 among three varieties to 4.14 to 4.20 mmol H2O/m2/s for ‘CGN 22091’ and ‘Peruvian Purple’ peppers. Water use efficiency (WUE; Pn/E) varied from 2.92 to 3.43 among three varieties to 5.10 to 7.20 for 16 other varieties. C. annuum derived varieties had higher Pn (9.4 μmol CO2/m2/s fixed) than varieties derived from other species (4.5–8.6 μmol CO2/m2/s fixed). Varieties originating from dry climates had higher Pn (12.5 μmol CO2/m2/s fixed) than those originating from temperate or tropical climates (8.0–8.8 μmol CO2/m2/s fixed). Tleaf (27 to 33 °C) and RH (38% to 39% and 57% to 59%) differed among varieties. Pn was positively correlated with g S, E, and RH and was negatively correlated with WUE. We found that Capsicum Pn, E, and g S varied more than has been previously reported, and our data suggested that Pn, g S, and E data of outdoor-grown peppers should be used only when selecting parents for a breeding program (unless progeny is intended for greenhouse production).