Plant biostimulants are microorganisms (PGPR) and/or products obtained from different organic substances that positively affect plant growth and efficiency and reduce the negative effects of abiotic challenges. Effects of biostimulants on the plant growth, yield, mineral content, antioxidant enzyme activity, H2O2, malondialdehyde (MDA), sucrose, and proline contents of cherry tomato (Solanum lycopersicum var. cerasiforme L.) grown in soils with two different characteristics were investigated during a pot study under greenhouse conditions. Soil I was a fertile routinely vegetable-cultivated soil. Soil II had high salinity, high CaCO3 content, and low organic matter content. Commercial biostimulant products Powhumus® (PH), Huminbio Microsense Seed® (SC), Huminbio Microsense Bio® (RE), and Fulvagra® (FU) were used as seed coatings and/or drench solutions. All biostimulant treatments improved the plant growth and yield compared with the control in both soils. All biostimulant applications were more effective in soil II than in soil I. RE was the most effective application for mineral content in soil I, whereas FU was the most effective in soil II. Antioxidant activity, H2O2, MDA, and proline contents were decreased in both soils when biostimulants were used compared with the control. Peroxide (POD) activity was greater with SC1 in soil II. The RE treatment increased the sucrose content in soil II. In conclusion, single and combined use of high-purity fulvic acid and PGPR had positive effects on the growth of cherry tomato in fertile soil and under stressed conditions.
Metin Turan, Ertan Yildirim, Melek Ekinci, and Sanem Argin
Ran Chen, Weitao Jiang, Haiyan Wang, Fengbing Pan, Hai Fan, Xuesen Chen, Xiang Shen, Chengmiao Yin, and Zhiquan Mao
Apple replant disease (ARD) has been reported in all major fruit-growing regions of the world and is often caused by biotic factors (pathogen fungi) and abiotic factors (phenolic compounds). Soil chemical fumigation can kill soil pathogenic fungi; however, the traditionally used fumigant methyl bromide has been banned because of its ozone-depleting effects. There is thus a need to identify greener fumigant candidates. We characterized the effects of different fumigants on the replanted soil environment and the growth characteristics of Malus hupehensis Rehd. seedlings. All five experimental treatments [treatment 1 (T1), metham-sodium; treatment 2 (T2), dazomet; treatment 3 (T3), calcium cyanamide; treatment 4 (T4), 1,3-dichloropropene; and treatment 5 (T5), methyl bromide] promoted significantly the biomass, root growth, and root respiration rate of M. hupehensis seedlings and the ammonium nitrogen (NH4 +-N) and nitrate nitrogen (NO3 –-N) contents of replanted soil. Metham sodium (T1) and dazomet (T2) had stronger effects compared with 1,3-dichloropropene (T4) and calcium cyanamide (T3). At 172 days after T1, the height, root length, and root respiration rate of Malus hupehensis Rehd. seedlings, and the NH4 +-N and NO3 –-N contents of replanted soil increased by 91.64%, 97.67%, 69.78%, 81.98%, and 27.44%, respectively, compared with the control. Thus, dazomet and metham sodium were determined to be the optimal fumigants for use in practical applications.
Fan-Hsuan Yang, David R. Bryla, and R. Troy Peters
Heat-related fruit damage is a prevalent issue in northern highbush blueberry (Vaccinium corymbosum L.) in various growing regions, including the northwestern United States. To help address the issue, we developed a simple climatological model to predict blueberry fruit temperatures based on local weather data and to simulate the effects of using over-canopy sprinklers for cooling the fruit. Predictions of fruit temperature on sunny days correlated strongly with the actual values (R 2 = 0.91) and had a root mean-square error of ≈2 °C. Among the parameters tested, ambient air temperature and light intensity had the greatest impact on fruit temperature, whereas wind speed and fruit size had less impact, and relative humidity had no impact. Cooling efficiency was estimated successfully under different sprinkler cooling intervals by incorporating a water application factor that was calculated based on the amount of water applied and the time required for water to evaporate from the fruit surface between the intervals. The results indicate that water temperature and nozzle flow rate affected the extent to which cooling with sprinklers reduced fruit temperature. However, prolonging the runtime of the sprinklers did not guarantee lower temperatures during cooling, because cooling efficiency declined as the temperature of the fruit approached the temperature of the irrigation water. Users could incorporate the model into weather forecast programs to predict the incidence of heat damage and could use it to make cooling decisions in commercial blueberry fields.
Ze-yuan Mi, Ding-hao Lv, Guang-hui Jiang, Jun-feng Niu, Shi-qiang Wang, and Zhe-zhi Wang
Bletilla striata (Thunb. ex A. Murray) Rchb. f., a species of perennial herb of orchidaceae that has remarkable effects and high economic value, has been intensively studied by many scholars. Although this herb has many seeds, the germination rate is exceptionally low, which leads to decreased germplasm resources and increased market demand every year. To solve this problem, this study examined the aseptic germination system and the direct seeding technology system. On Murashige and Skoog (MS) medium, 2.0 mg/L 6-benzylaminopurine (6-BA) and 1.0 mg/L naphthylacetic acid (NAA) were added before seed germination, and 70 g/L banana juice and 0.5 mg/L NAA were added when rooting. Then, the seedlings were transplanted to a mixed substrate of humus, river sand, and bark (volume ratio of 3:1:1). The direct seeding system consists of substrate treatment, sowing, seedling raising, seedling growth, and transplanting. Turfy soil, Huangjiang residue, and river sand were selected as the substrate. The results revealed that the germination rate was increased to 91.8%, whereas the plantlet regeneration was increased to 82.0%. After 180 days of cultivation, the plants could be transplanted as finished seedlings. The establishment of B. striata seedling system provides a safe, rapid, reliable production technology route for industrial development.
Lyn A. Gettys, Kyle L. Thayer, and Joseph W. Sigmon
The foundation of most aquatic weed management programs in Florida is synthetic herbicides because many of these U.S. Environmental Protection Agency (USEPA)-registered products are effective, selective, and inexpensive compared with other strategies such as mechanical harvesting. However, stakeholders have expressed concern regarding their use and managers are interested in exploring alternative methods for aquatic weed control. To that end, we evaluated the efficacy, selectivity, and costs of the “natural” products acetic acid and d-limonene (alone and in combination with each other and citric acid) on the invasive floating plants waterhyacinth (Eichhornia crassipes) and waterlettuce (Pistia stratiotes), and the native emergent plants broadleaf sagittaria (Sagittaria latifolia) and pickerelweed (Pontederia cordata). These products, plus an industry-standard synthetic herbicide (diquat dibromide), were applied once as foliar treatments to healthy plants, which were grown out for 8 weeks after treatment to allow development of phytotoxicity symptoms. A 0.22% concentration of diquat dibromide eliminated all vegetation, but neither “natural” product alone provided acceptable (>80%) control of floating weeds, even when applied at the maximum concentrations under evaluation (20% acetic acid, 30% d-limonene). Citric acid (5% or 10%) had no effect on the activity of acetic acid or d-limonene, but some combinations of acetic acid and d-limonene controlled floating weeds effectively without causing unacceptable damage to native plants. However, these treatments are much more expensive than the synthetic standard and managers would realize a 22- to 26-fold increase in product cost alone without factoring in other expenses such as additional labor and application time. Combinations of acetic acid and d-limonene may have utility in some areas where the use of synthetic herbicides is discouraged, but broad-scale deployment of this strategy would likely be prohibitively expensive.
Dong Sub Kim, Steven Kim, and Steven A. Fennimore
Soil disinfestation with steam has potential to partially replace fumigants such as methyl bromide, chloropicrin, and 1,3-dichloropropene because it is effective, safer to apply, and has less negative impact on the environment. Here, we compared the efficacy of steam and steam + mustard seed meal (MSM) to chloropicrin on soil disinfection, plant growth, and fruit yield in a strawberry (Fragaria ×ananassa) fruiting field. The MSM was applied at 3368 kg·ha−1 before the steam application. Steam was injected into a 3-m-wide reverse tiller that was set to till 30 to 40 cm deep. Soil temperatures at depths of 10, 20, 25, and 35 cm were monitored. Steam and steam + MSM treatments reduced the viability of purslane seeds and nutsedge tubers, microsclerotia density of Verticillium dahliae, propagule density of Pythium ultimum, cumulative weed densities, and biomass compared with the nontreated control. Moreover, the steam application was as efficacious as chloropicrin on these pests. The growth and fruit yield of strawberries grown on soils previously treated with the steam and steam + MSM treatments were similar to those in the chloropicrin treatment and were higher than those in the nontreated control. Our study indicated that steam, steam + MSM, and chloropicrin are equally effective at suppressing weeds and soilborne pathogens. These results suggest that the steam and steam + MSM treatment can be a practical alternative for soil disinfestation in conventional and organic strawberry fields.
Laban K. Rutto, Zelalem Mersha, and Mizuho Nita
The French American hybrid grape cultivars Corot noir and Arandell (Vitis sp.), and Vidal blanc and Petit Manseng (Vitis vinifera), along with different spray programs, were evaluated for potential organic production in Virginia from 2013 to 2014. Results obtained in the study demonstrate that organic wine grape production in Virginia can be achieved by using select grape cultivars and spray programs. With the exception of Vidal blanc, disease severity and disease incidence were below the threshold for maintaining healthy vines in all organically managed grape cultivars. ‘Vidal blanc’ was not sufficiently resistant to downy mildew (Plasmopara viticola), precluding it from potential organic management in Virginia. The study also demonstrated significant disease resistance in Virginia of the cultivar Arandell, released by Cornell University (Ithaca, NY) in 2013. The results suggest that the organically registered fungicide Bacillus subtilis is effective in reducing the severity and incidence of black rot (Guignardia bidwellii) and phomopsis cane and leaf spot (Phomopsis viticola). The chemistry of organically managed berries harvested in 2014 met minimum requirements for wine production with soluble solids, titratable acidity, and pH ranging from 18.7% to 20.2%, 7.6 to 8.0 g·L−1, and 3.3 to 3.4, respectively, in ‘Arandell’ and ‘Corot noir’; and 21.0% to 24.4%, 7.8 to 9.6 g·L−1, and 2.7 to 2.9, respectively, in ‘Petit Manseng’ and ‘Vidal blanc’ juice.
Jiwoo Park and James E. Faust
The amount of fertilizer applied during the commercial production of bedding plants has decreased in recent years because of increasing concerns about environmental impacts and the need to minimize production costs. However, reduced fertilization affects plant growth and flowering during production and in the postproduction environment. Plants grown with lower nutrient levels may perform satisfactorily during greenhouse production, but they may possess insufficient nutrients to sustain further growth in the postproduction environment, where fertilizer application is frequently lacking. This study examined conventional and alternative fertilizer delivery strategies that produce high-quality petunia (Petunia ×hybrida) during greenhouse production and continue to support plant growth and flowering in the postproduction environment. The fertilizer treatments during production consisted of four constant liquid fertilization (CLF) treatments of 0, 50, 100, or 200 ppm nitrogen (N) and three controlled-release fertilization (CRF) treatments (0, 4, or 8 lb/yard3). Three pulse fertilization (PF) treatments (0, 300, or 600 ppm N) were applied immediately before moving the plants to the postproduction environment. During production, petunia growth and development increased as CLF increased from 0 to 200 ppm N, but the addition of CRF resulted in the increase occurring at a declining rate. During postproduction, the interactive effects of CLF and CRF continued in a similar pattern as that seen in the production environment. The additional PF treatments resulted in further increases in plant growth. Across all CLF and CRF treatments, the leaf area increased from 466 to 540 cm2 as PF increased from 0 to 300 ppm N, and the leaf area increased further to 631 cm2 as PF increased from 300 to 600 ppm N. Based on our findings, two alternative strategies are possible. First, 0 to 50 ppm N CLF can be combined with 4 lb/yard3 CRF. The second strategy maintains the standard commercial practice of applying 100 ppm N CLF treatment and then applying a 300- to 600-ppm N PF treatment. These results suggest that a relatively low CLF rate can be used to achieve the desired production characteristics while reducing the cost of plant growth regulation, and that additional plant nutrition can be provided with CRF and/or PF to enhance the postproduction performance.
Tao Yuan, Qiuying Wei, Pablo Jourdan, and Yong Kwon Yoo
Pulsatilla cernua var. koreana seeds were harvested at six different dates between 16 days after flowering (DAF) (8 Apr.) and 43 DAF (5 May) in 2018 and categorized into six groups based on X-ray images. Germination tests were performed without and with 2 weeks of moist 5 °C treatment [cold stratification (CS)]. Seeds harvested at 38 DAF (30 Apr.) with well-developed vegetative organs (embryo and endosperm) in seeds categorized as A and B (seed A and seed B, respectively) based on the X-ray images were considered fully developed, and 80% of seeds were considered mature. However, the germination rates were less than 26% or 28% when full seeds harvested at 43 DAF received no or 14 days of CS treatment, respectively. Our study suggests that the low germination rate of fully developed seeds as judged by X-ray images showing well-developed embryo and endosperm could result from the presence of dormancy that was not broken effectively by 14 days of CS coupled with the loss of viability caused by 8 months of dry storage at 5 °C.
Eric T. Stafne and Barbara J. Smith
Rabbiteye blueberry (Vaccinium virgatum) bushes are relatively easy to grow and commonplace across Mississippi; however, if not properly maintained, the bushes will decline over time. Eighteen, aged, low-productivity ‘Woodard’ rabbiteye blueberry bushes were pruned at two different heights (ground level and a 50-cm above ground level) after harvest in July 2017, and phosphorous acid was applied as a drench and foliar spray in the first year, but this was discontinued as the applications had no effect on the bushes. For two seasons, fruit yields were collected and weighed, bushes were measured for growth parameters, and canes were weighed. Bushes pruned at the 50-cm above ground level had much higher yields in both 2019 (3.47 vs. 0.63 kg) and 2020 (3.91 vs. 1.23 kg), thus providing a substantial yield benefit. The 50-cm above ground level pruning treatment bushes produced more canes by the end of the study, therefore accounting for more fruiting area, as seen in the harvest index. In short, pruning old, nonproductive bushes at a 50-cm above ground level can provide growers with greater potential for early economic returns than pruning at ground level, for ‘Woodard’ rabbiteye blueberry.