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The efficacy of the fungicide pydiflumetofen + difenoconazole (Postiva) was evaluated at varying application rates and intervals to control black spot disease (Diplocarpon rosae) in rose (Rosa spp. ‘Coral Drift’). Container-grown roses were arranged in a completely randomized design with five single-plant replications. Experiments were conducted under greenhouse and shade-house conditions (56% shade) in 2021/2022 and 2023. Black spot disease in roses was developed naturally. Pydiflumetofen + difenoconazole at 1.1 , 1.6, and 2.2 mL⋅L–1, and standard fungicide azoxystrobin + benzovindiflupyr (Mural) at 0.5⋅g L–1 were sprayed on foliage to runoff on a 2- or 4-week interval. Plants that were not treated with fungicide served as the controls. Plants were evaluated weekly for disease severity (0%–100% foliage affected) and defoliation (0%–100% defoliation). The season-long area under the disease progress curve (AUDPC) and area under the defoliation progress curve (AUDFC) were calculated for the evaluation period. Pydiflumetofen + difenoconazole reduced significantly black spot disease severity, AUDPC, defoliation, and AUDFC both in greenhouse and shade-house conditions compared with control plants, and was as effective as azoxystrobin + benzovindiflupyr. All the application rates and intervals of pydiflumetofen + difenoconazole were equally effective in reducing black spot severity and AUDPC. Our findings suggest that pydiflumetofen + difenoconazole at the lowest rate with the longest application interval is the most cost-effective, and has similar efficacy as treatments with higher rates and more frequent intervals.

Open Access

Flow cytometry has been widely used to estimate relative and absolute genome sizes (DNA contents) of plants for more than 50 years. However, the accuracy of these estimates can vary widely because of many factors, including errors in the genome size estimates of reference standards and various experimental methods. The objectives of this study were to reassess genome sizes of commonly used reference standards and quantify sources of variation and error in estimating plant genome sizes that arise from buffers, confounding plant tissues, tissue types, and plant reference standards using both 4′,6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI) fluorochromes. Five separate studies were performed to elucidate these objectives. Revised estimates of genome sizes of commonly used plant reference standards were determined using human male leukocytes as a primary standard with an updated genome size (6.15 pg; 12.14% lower than that of earlier studies) using both DAPI and PI fluorochromes. Comparison of six different buffers (Galbraith’s, LB01, MB01, MgSO4, Otto’s, and Sysmex) resulted in variations in genome size estimates by as much as 18.1% for a given taxon, depending on the buffer–fluorochrome combination. The addition of different confounding plant tissues (representing 10 diverse taxa and associated secondary metabolites) resulted in variations in genome size estimates by as much as 10.3%, depending on the tissue–fluorochrome combination. Different plant tissue types (leaf color/exposure and roots) resulted in a variation in genome size estimates of 10.7%, independent of the fluorochrome. The selection of different internal reference standards introduced an additional variation in genome size estimates of 5.9%, depending on the standard–fluorochrome combination. The choice of fluorochrome (DAPI vs. PI) had one of the largest impacts on genome size estimates and differed by as much as 32.9% for Glycine max ‘Polanka’ when using human male leukocytes as an internal standard. A portion of this variation (∼10.0%) can be attributed to the base pair (bp) bias of DAPI and variations in Guanine-Cytosine (GC):Adenine-Thymine (AT) ratios between the sample and standard. However, as much as 22.9% of the variation in genome size estimates may result from how effectively these fluorochromes stain and report the genome. The combined variation/error from all these factors (excluding variation from bp bias for different fluorochromes, and assuming variations from confounding tissues and tissue types to both result from secondary metabolites) totaled 57.6%. Additional details of how selected factors impact accuracy, precision, and the interaction of these factors are presented. Overall, flow cytometry can be precise, repeatable, and extremely valuable for determining the relative genome size and ploidy of closely related plants when using consistent methods, regardless of fluorochrome. However, accurate determination of the absolute genome size by flow cytometry remains elusive, and estimates of genome size using flow cytometry should be considered gross approximations that may vary by ±29% or more as a function of experimental methods and plant environments. Additional recommendations of best practices are provided.

Open Access

Cancer bush (Lessertia frutescens L.) is an important medicinal plant that is rich in health beneficial compounds. It is commonly used in traditional medicine and as an ornamental plant. Heat stress is the most threatening abiotic factor restricting plant growth, thus causing crop yield and economic losses worldwide. The application of plant-derived biostimulant is as an innovative and promising approach for improving plant growth and productivity. The study was aimed to investigate the effect of moringa (Moringa oleifera Lam.) seed extract (MSE; 5%) either alone or in combination with salicylic acid (SA; 40 mg/L) on the growth, bioactive, and phytohormone attributes of cancer plants subjected to heat stress (38 °C for 2 hours for 5 days). Plants that were not treated were used as control. Plant pots were arranged in a randomized complete block design (RCBD) for treatments (MSE, SA, and MSE + SA) at 7-day intervals during the experiment. Both MSE and MSE + SA foliar application effectively increased plant growth characteristics and total carotenoids contents, and reduced electrolyte leakage and had no symptoms of wilting compared with SA and control. Plants treated with MSE showed higher number of branches and concentrations of abscisic acid (ABA), jasmonic acid (JA), and indole-3-acetic acid (IAA), and lower superoxide and hydrogen peroxide compared with other treatments and control. Also, plants treated with MSE + SA showed higher total chlorophylls and glutathione concentrations compared with other treatments and control. Overall, the application of MSE either alone or in combination with SA enhanced plant growth and productivity of heat-stressed cancer bush plants.

Open Access

Traditional methods of garlic fertilization involve large amounts of balanced fertilizer with equal proportions of N, P, and K, leading to nutrient imbalances, reduced yield and nutritional quality, and elevated risk of environmental pollution. This study for the first time measured garlic nutrient absorption and mineral elements status in garlic fields. In addition, a garlic-specific fertilizer formula and recommended rate were designed and applied in multiple garlic fields during the 2019–21 growing season. We assessed the performance of garlic-specific fertilizer in terms of yield, quality, and nutrient utilization efficiency. We showed that garlic prefers to absorb N and K, and its absorption of P was much lower. Deficiencies in Cl, Mn, S, and Fe are found in 98.7%, 56.1%, 22.8%, and 11.9% of garlic fields. Compared with farmer fertilization, the garlic-specific fertilizers increased sprout yield by 12.9% to 30.5%, bulb yield by 11.0% to 33.5%, and net income by 18.2% to 45.6%. Furthermore, it improved the nutritional quality [vitamin C (Vc), soluble sugar (SS), and soluble protein] of the garlic and reduced the accumulation of nitrate. The formula of special fertilizer was more in line with the law of garlic nutrient absorption, increasing the nutrient utilization effect, reducing the environmental risks. Application of specific fertilizer increased N, P, and K partial productivity by 26.6% to 50.1%, 82.6% to 116.5%, and 54.6% to 83.3%, respectively. These results suggest that replacing balanced fertilizers in the garlic market with garlic-specific fertilizers can improve garlic farmers' incomes and soil health.

Open Access

In 2020, the COVID-19 pandemic changed the way many businesses conducted business. Notably, regulations imposed by states impacted how green-industry firms sold their plants and landscape products. However, not all states implemented the same stringency of regulations. Using an online consumer survey implemented in Jan 2021, we examine the impact of varying regulation stringencies across five treatment groups (Michigan, and New York, and low, medium, and high stringency). We estimate the difference between 2020 and 2019 self-reported expenditures, in conjunction with propensity score matching to compare each treatment with the other treatments. Results indicate that, for the most part, states with greater stringency associated with their COVID regulations did not impact plant and landscape expenditures negatively between 2019 and 2020. However, Michigan consumers did spend significantly less than medium- and high-stringency states for landscape products. Michigan was one of only two states that put qualifications on green-industry firms, and it was the only state to list green-industry firms as nonessential. Also, New York consumers spent more than low-stringency states, and low-stringency states spent less than high-stringency states for plants. Furthermore, there were no differences in online expenditures between state treatment groups. From a policy perspective, regulation type (i.e., shutting down green-industry sectors as Michigan did) had varying impacts across product categories within the green industry.

Open Access

Phalaenopsis is a globally popular potted plant possessing a few aromatic cultivars, but analysis of volatile organic compounds (VOCs) in these cultivars is limited. Here, using nonaromatic cultivar Phal. Big Chili as a control, flower VOCs of four aromatic cultivars were investigated by headspace solid-phase microextraction in conjunction with gas chromatography–mass spectrometry (GC-MS). The results revealed that 43 VOCs classified into seven categories were identified in the nonaromatic Phal. Big Chili and four aromatic cultivars. Hexyl acetate and hexan-1-ol were common VOCs in aromatic cultivars. On the basis of partial least squares discriminant analysis, the five cultivars were classified into three groups, the nonaromatic Phal. Big Chili (group 1) and the strong-aromatic Phal. Cherry Tomato (group 2) were easily distinguished from the other three aromatic cultivars (group 3). Moreover, 17 key VOCs with the different aromatic thresholds and characteristics were identified in the four aromatic cultivars, and the types and relative contents of key VOCs varied among the aromatic cultivars, resulting in different characteristics and intensities of floral fragrance in aromatic cultivars. In aromatic cultivars, the types and relative contents of key VOCs in Phal. Cherry Tomato significantly exceeded those in the other three cultivars. Eight key VOCs belonging to terpenoids, olefins, and alcohols had the highest relative contents in Phal. ‘Cherry Tomato’, which led to a strong and mixed aromatic type containing cedarwood, camphor, and mint fragrances.

Open Access

The onion processing industry produces hundreds of thousands of tons of onion waste annually. Normally, onion peel waste is dumped in landfills, which creates additional sources of greenhouse gases. Research has validated that onion peel is a concentrated source of bioactive compounds; therefore, it can be turned into useful agricultural products such as soil amendments and possibly biostimulants. This study conducted three experiments to investigate the plant growth-promoting potential of an onion juice concentrate (OJC). The first experiment explored whether the application of OJC could increase plant growth of Bermuda grass, lettuce, and bok choy. The second experiment evaluated the effects of foliar and subsurface drench applications of OJC on bok choy and lettuce growth. The third experiment investigated the interaction between OJC application methods and fertilizer type on bok choy and radish growth. The results indicated that foliar applications of OJC of 1% to 2% concentrations increased the yield of bok choy and its overall growth. Subirrigation with OJC, however, enhanced the root growth of bok choy, lettuce, and radish. Notably, the combined approach of foliar and subirrigation applications further promoted the growth of both bok choy and radish. Comparing across experiments, longer OJC application periods emerged as a promising strategy for amplifying its growth-promoting benefits. Overall, our findings suggest that OJC holds promise for promoting sustainable agriculture. This potential comes from its ability to enhance both the growth and yield of vegetable crops like bok choy, lettuce, and radish while simultaneously reducing waste.

Open Access