Influences of nitrogen inputs on nematode populations under highbush blueberry.

This study examined the effects of nitrogen fertilization on populations of Rotylenchus robustus, Pratylenchus crenatus, and Paratrichodorus renifer, and indices of free-living nematode community structure, in relation to highbush blueberry production in British Columbia, Canada. The field experiment was established in fall of 2008 with six replicate plots of each of four experimental N fertilization treatments: 0, 100, 150, and 200% of the annual application rate recommended for conventional blueberry production in the region. Nematode populations were quantified annually from 2009 through 2015, and then nematode populations and root biomass were quantified at seven sample dates from 2016 through 2019. Population densities of R. robustus were consistently greater in the 100% treatment than in the 0, 150, and 200% treatments which did not differ from each other. Population densities of P. crenatus were consistently greater in the 150% treatment than in the 0, 100%, and 200% treatments. The nematode structure index and two indices of diversity declined monotonically with N fertilizer rate, indicating broader changes in the soil food web that could have had indirect, feedback effects on population dynamics of the plant-parasitic nematodes.This study examined the effects of nitrogen fertilization on populations of Rotylenchus robustus, Pratylenchus crenatus, and Paratrichodorus renifer, and indices of free-living nematode community structure, in relation to highbush blueberry production in British Columbia, Canada. The field experiment was established in fall of 2008 with six replicate plots of each of four experimental N fertilization treatments: 0, 100, 150, and 200% of the annual application rate recommended for conventional blueberry production in the region. Nematode populations were quantified annually from 2009 through 2015, and then nematode populations and root biomass were quantified at seven sample dates from 2016 through 2019. Population densities of R. robustus were consistently greater in the 100% treatment than in the 0, 150, and 200% treatments which did not differ from each other. Population densities of P. crenatus were consistently greater in the 150% treatment than in the 0, 100%, and 200% treatments. The nematode structure index and two indices of diversity declined monotonically with N fertilizer rate, indicating broader changes in the soil food web that could have had indirect, feedback effects on population dynamics of the plant-parasitic nematodes.

Forest tree extracts induce resistance to Pseudomonas syringae pv. tomato in Arabidopsis.

The widespread use of conventional pesticides for plant pathogen control poses significant risks to human health and the environment, and it is therefore crucial to develop environmentally friendly, human-safe alternatives to these products that offer a sustainable approach for crop protection. Here, we examined the potential of ethanolic extracts from four forest tree species for their antibacterial activity against the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) and their ability to trigger effective defense responses in the model plant Arabidopsis thaliana. The extracts exhibited direct toxic effects against Pst and triggered the expression of defense-related genes naturally induced by oxidative stress cues or the defense elicitor salicylic acid in leaf tissue. The direct antibacterial effects of the tree extracts, together with their defense gene-inducing effects in planta, resulted in a strong host plant-protecting effect against Pst. These findings suggest the eventual effectiveness of forest tree extracts as plant protectants against the bacterial pathogen Pst. They also suggest the potential of these extracts as a sustainable, eco-friendly alternative to conventional pesticides for the management of economically important plant pathogens.

Suppressive Effect of Black Soldier Fly Larvae Frass on Fusarium Wilt Disease in Tomato Plants.

This study investigated the effect of black soldier fly larvae (BSFL) frass derived from BSFL reared on a diet composed of fruit/vegetable/bakery/brewery residues (FVBB diet) and on the Gainesville diet (GV diet) on the development of tomato (Solanum lycopersicum) Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (FOL). Tomato plants were grown in a substrate inoculated with FOL that was amended (10%, v:v) or not (control) with either a commercial compost, pasteurized (70 °C for 1 h) frass from BSFL reared on a FVBB diet, non-pasteurized frass from BSFL reared on a FVBB diet, pasteurized frass from BSFL reared on the GV diet, or non-pasteurized frass from BSFL reared on the GV diet. The results show that frass from BSFL reared on the GV diet, irrespective of pasteurization, inhibited FOL root colonization and reduced the severity of tomato Fusarium wilt to a far greater extent than frass from BSFL reared on a FVBB diet and commercial compost made of peat, seaweed, and shrimps. This study suggests that BSFL frass, depending on the larval rearing diet, has the potential to serve as a pasteurized or non-pasteurized soil amendment with prophylactic properties against FOL in tomato plants, opening new avenues of research for the valorization of BSFL frass.

Simultaneous removal of nitrate and sulfate from greenhouse wastewater by constructed wetlands.

This study evaluated the effectiveness of C-enriched subsurface-flow constructed wetlands in reducing high concentrations of nitrate (NO) and sulfate (SO) in greenhouse wastewaters. Constructed wetlands were filled with pozzolana, planted with common cattail (), and supplemented as follows: (i) constructed wetland with sucrose (CW+S), wetland units with 2 g L of sucrose solution from week 1 to 28; (ii) constructed wetland with compost (CW+C), wetland units supplemented with a reactive mixture of compost and sawdust; (iii) constructed wetland with compost and no sucrose (CW+CNS) from week 1 to 18, and constructed wetland with compost and sucrose (CW+CS) at 2 g L from week 19 to 28; and (iv) constructed wetland (CW). During 28 wk, the wetlands received a typical reconstituted greenhouse wastewater containing 500 mg L SO and 300 mg L NO. In CW+S, CW+C, and CW+CS, appropriate C:N ratio (7:3.4) and redox potential (-53 to 39 mV) for denitrification resulted in 95 to 99% NO removal. Carbon source was not a limiting factor for denitrification in C-enriched constructed wetlands. In CW+S and CW+CS, the dissolved organic carbon (DOC)/SO ratios of 0.36 and 0.28 resulted in high sulfate-reducing bacteria (SRB) counts and high SO removal (98%), whereas low activities were observed at DOC/SO ratios of 0.02 (CW) to 0.11 (CW+C, CW+CNS). On week 19, when organic C content was increased by sucrose addition in CW+CS, SRB counts increased from 2.80 to 5.11 log[CFU+1] mL, resulting in a level similar to the one measured in CW+S (4.69 log[CFU+1] mL). Consequently, high sulfate reduction occurred after denitrification, suggesting that low DOC (38-54 mg L) was the limiting factor. In CW, DOC concentration (9-10 mg L) was too low to sustain efficient denitrification and, therefore, sulfate reduction. Furthermore, the high concentration of dissolved sulfides observed in CW+S and CW+CS treated waters were eliminated by adding FeCl.

Use of a passive bioreactor to reduce water-borne plant pathogens, nitrate, and sulfate in greenhouse effluent.

The goal of this study was to evaluate the use of passive bioreactors to reduce water-borne plant pathogens (Pythium ultimum and Fusarium oxysporum) and nutrient load (NO(-) 3 and SO(2-) 4) in greenhouse effluent. Sterilized and unsterilized passive bioreactors filled with a reactive mixture of organic carbon material were used in three replicates. After a startup period of 2 (sterilized) or 5 (unsterilized) weeks, the bioreactor units received for 14 weeks a reconstituted commercial greenhouse effluent composed of 500 mg L(-1) SO(2-) 4 and 300 mg L(-1) NO(-) 3 and were inoculated three times with P. ultimum and F. oxysporum (10(6) CFU mL(-1)). Efficacy in removing water-borne plant pathogens and nitrate reached 99.9% for both the sterilized and unsterilized bioreactors. However, efficacy in reducing the SO(2-) 4 load sharply decreased from 89% to 29% after 2 weeks of NO(-) 3-supply treatment for the unsterilized bioreactors. Although SO(2-) 4 removal efficacy for the sterilized bioreactors did not recover after 4 weeks of NO(-) 3-supply treatment, the unsterilized bioreactor nearly reached a similar level of SO(2-) 4 removal after 4 weeks of NO(-) 3-supply treatment compared with affluent loaded only with SO(2-) 4, where no competition for the carbohydrate source occurred between the denitrification process and sulfate-reducing bacteria activity. Performance differences between the sterilized and unsterilized bioreactors clearly show the predominant importance of sulfate-reducing bacteria. Consequently, when sulfate-reducing bacteria reach their optimal activity, passive bioreactors may constitute a cheap, low-maintenance method of treating greenhouse effluent to recycle wastewater and eliminate nutrient runoff, which has important environmental impacts.

Different Temperature and UV Patterns Modulate Berry Maturation and Volatile Compounds Accumulation in Vitis sp.

Volatile compounds (VCs) in grapevine berries play an important role in wine quality; however, such compounds and vine development can be sensitive to environmental conditions. Due to this sensitivity, changes in temperature patterns due to global warming are likely to further impact grape production and berry composition. The aim of this study was to determine the possible effects of different growing-degree day accumulation patterns on berry ripening and composition at harvest. An experimental field was conducted using Vitis sp. L'Acadie blanc, in Nova Scotia, Canada. Using on-the-row mini-greenhouses, moderate temperature increase and reduced ultraviolet (UV) exposure were triggered in grapevines during pre-veraison (inflorescence to the beginning of berry softening), post-veraison (berry softening to full maturity), and whole season (inflorescence to full maturity), while controls were left without treatment. Free and bound VCs were extracted from berries sampled at three different phenological stages between veraison and maturity before analysis by gas chromatography-mass spectrometry (GC-MS). Berries from grapevines exposed to higher temperatures during early berry development (pre-veraison and whole) accumulated significantly higher concentrations of benzene derivatives 2-phenylethanol and benzyl alcohol at harvest, but lower concentrations of hydroxy-methoxy-substituted volatile phenols, terpenes, and C13-norisoprenoids than the control berries. These results illustrate the importance of different environmental interactions in berry composition and suggest that temperature could potentially modulate phenylpropanoid and mevalonate metabolism in developing berries. This study provides insights into the relationships between abiotic conditions and secondary metabolism in grapevine and highlights the significance of early developmental stages on berry quality at harvest.

Nutrients Leaching in Response to Long-Term Fertigation and Broadcast Nitrogen in Blueberry Production.

Nutrient leaching losses from horticultural production threaten the quality of groundwater and freshwater systems worldwide. The objectives of this study were to (a) assess the effects of annual applications of ammonium sulfate fertilizer through fertigation (FERT) and broadcast (BROAD) on nutrient leaching losses and (b) determine the links among chemical property changes in leachates and soil with berry yields after 9 and 11 years of blueberry production. The long-term blueberry site was established in 2008 using seven combinations of treatments including an unfertilized control (CONT) and three N fertilizer rates (100%, 150%, 200% of recommended rates) using BROAD and FERT methods. Nutrients concentrations (NO3--N, NH4+-N and SO42--S) and chemical properties (pH and electrical conductivity (EC)) of leachate, sawdust and soil and berries were assessed. All FERT methods resulted in concentrations of NO3--N in the leachates > 100 mg L-1 with a maximum of 200 mg L-1 for FERT-200 during the growing season due to the easy transport of dissolved nutrients with the irrigation water. All BROAD methods resulted into concentrations of NO3--N in the leachates >10 mg L-1 with a maximum of 35 mg L-1 for BROAD-200 between April and July, as well as between November and April, indicating two periods of NO3--N leaching losses. The pattern observed with BROAD indicates that irrigation water in the summer and heavy rainfall in the winter contribute to NO3--N leaching losses. Concentrations of NH4+-N in the leachates >1 mg L-1 were measured under FERT with a peak at 64.78 mg L-1 for FERT-200, during the period April to August, due to NH4+'s ability to quickly move through the sawdust layer with irrigation water. Principal component analysis linked berry yield decrease with ammonium sulfate applications above recommended rates (FERT and BROAD) and with changes in soil pH and EC. Our results demonstrated that excess fertilizer applications above recommended rates using FERT and BROAD can threaten the sustainability of blueberry production by enhancing nutrient leaching losses and reducing berry yield.

Multivariate approach to the measurement of tomato maturity and gustatory attributes and their rapid assessment by Vis-NIR spectroscopy.

Standard methods for determining quality and maturity are time- and labor-consuming and generally measure individual criteria at a specific time, without considering relationships among quality parameters. To propose a rapid and nondestructive analysis method describing multidimensional quality variables, an experiment was undertaken with mature green to overripe tomato fruits found on the North American retail markets. Factor analysis was used to analyze results. Four factors were considered, representing 81% of total variance. The first one, tomato maturity stage (TMS), is related to color, lycopene content, firmness, titratable acidity (TA), pH, and soluble solids (SS). Nondestructive rapid assessment by vis-NIR spectroscopy can predict TMS (r(2)=0.93). Factors 2 and 3 are both related to taste and should be considered simultaneously. Factor 2, called the gustatory index, is linked to electrical conductivity (EC), SS, TA, and pH. Factor 3, defined by SS, can be directly measured by a refractometer. Four categories of taste are proposed; the most desirable one ranks high both in soluble solids (above 4.5 degrees Brix) and in gustatory index (above 0). It was not possible to measure the gustatory index by vis-NIR spectroscopy (r(2)=0.17), but it can be estimated by EC, using a simple formula. The proposed limit between high and low gustatory index then corresponds to an EC of 5.4 mS/cm. Factor 4, variety, mostly discriminates the pink tomato type and field-grown samples from other varieties.

Organic Nitrogen Uptake and Assimilation in Cucumis sativus Using Position-Specific Labeling and Compound-Specific Isotope Analysis.

Organic nitrogen is now considered a significant source of N for plants. Although organic management practices increase soil organic C and N content, the importance of organic N as a source of crop N under organic farming management systems is still poorly understood. While dual-labeled (13C and 15N) molecule methods have been developed to study amino acid uptake by plants, multiple biases may arise from pre-uptake mineralization by microorganisms or post-uptake metabolism by the plant. We propose the combination of different isotopic analysis methods with molecule isotopologues as a novel approach to improve the accuracy of measured amino acid uptake rates in the total N budget of cucumber seedlings and provide a better characterization of post-uptake metabolism. Cucumber seedlings were exposed to solutions containing L-Ala-1-13C,15N or U-L-Ala-13C3,15N, in combination with ammonium nitrate, at total N concentrations ranging from 0 to 15 mM N and at inorganic/organic N ratios from 10:1 to 500:1. Roots and shoots were then subjected to bulk stable isotope analysis (BSIA) by Isotope Ratio Mass Spectrometry (IRMS), and to compound-specific stable isotope analysis (CSIA) of the free amino acids by Gas Chromatography - Combustion - Isotope Ratio Mass Spectrometry (GC-C-IRMS). Plants exposed to a lower inorganic:organic N ratio acquired up to 6.84% of their N from alanine, compared with 0.94% at higher ratio. No 13C from L-Ala-1-13C,15N was found in shoot tissues suggesting that post-uptake metabolism of Ala leads to the loss of the carboxyl-C as CO2. CSIA of the free amino acids in roots confirmed that intact Ala is indeed taken up by the roots, but that it is rapidly metabolized. C atoms other than from the carboxyl group and amino-N from Ala are assimilated in other amino acids, predominantly Glu, Gln, Asp, and Asn. Uptake rates reported by CSIA of the free amino acids are nevertheless much lower (16-64 times) than those reported by BSIA. Combining the use of isotopologues of amino acids with compound-specific isotope analysis helps reduce the bias in the assessment of organic N uptake and improves the understanding of organic N assimilation especially in the context of organic horticulture.

Silicon Transporters and Effects of Silicon Amendments in Strawberry under High Tunnel and Field Conditions.

Together with longer production periods, the commercial transition to day-neutral strawberry (Fragaria × ananassa) varieties has favored the development of diseases such as powdery mildew (Podosphaera aphanis) that thrives in late summer-early fall. In an attempt to find alternative solutions to fungicides currently employed to curb the disease, we wanted to investigate the potential of silicon (Si) amendments that have been associated with prophylactic properties against powdery mildews. To this end, our first objective was to determine if strawberry was a Si-competent species following the recent characterization of the properties of Si transporters that plants must carry to uptake silicic acid. Based on genomic data, we were able to conclude that strawberry contained both functional influx (Lsi1) and efflux (Lsi2) transporters for Si uptake. Subsequently commercial experiments under high tunnel and field conditions were conducted with different Si fertilization regimes: constant soluble Si feeding in high tunnel, and bi-weekly soluble Si feeding or three concentrations of calcium silicate fertilization in the field. Results from high tunnel experiments showed that strawberry could accumulate as much as 3% Si on a dry-weight basis, the highest concentration ever reported for this species. All six tested cultivars contained roughly the same concentration, thereby confirming the limited genetic variability, also observed in other species, associated with the trait. Silicon fertilization under high tunnel led to a significant reduction of powdery mildew severity in both years and on all cultivars, and a significant increase in yield of marketable fruits reaching as much as 300% with cv. Monterey. By contrast, Si fertilization under field conditions in soils deficient in plant available Si, either in soluble or solid form, did not result in significant accumulation of Si in plants, regardless of the cultivars, year or concentrations. Our results have thus provided both genotypic and phenotypic proof that strawberry can greatly benefit from Si fertilization, but have also highlighted the importance of validating the fertilization regime to ensure that Si is properly absorbed and/or available to the plant.

Understory light and root ginsenosides in forest-grown Panax quinquefolius.

The objective of this study was to determine the relationship between light levels in the understory of a broadleaf forest and the content of six ginsenosides (Rg(1), Re, Rb(1), Rc, Rb(2,) and Rd) in 1- and 2-year-old American ginseng (Panax quinquefolius L.) roots. Our results revealed that ginsenoside contents in 1- and 2 year-old roots collected in September were significantly related to direct and total light levels, and duration of sunflecks. At this time, the effect of light levels accounted for up to 48 and 62% of the variation in ginsenoside contents of 1- and 2-year-old American ginseng roots. Also, red (R) and far red (FR) light, and the R:FR ratio significantly affected Rd, Rc, and Rg(1) contents in 2-year-old roots, accounting for up to 40% of the variation in ginsenoside contents.

Flavor of cold-hardy grapes: impact of berry maturity and environmental conditions.

Since the arrival on the market of high-quality cold-hardy grape varieties, northern winemaking has been developing tremendously in countries traditionally unsuited for grape and wine production. Cold-hardy grapes are mainly interspecific hybrids of Vitis vinifera with Vitis labrusca and Vitis riparia , making their chemical composition distinct from that of V. vinifera varieties traditionally used for winemaking and therefore limiting the use of current knowledge about V. vinifera varieties in the assessment of grape maturity. Consequently, to evaluate the flavor development of cold-hardy grapes in the province of Quebec, Canada, the ripening of Frontenac and Marquette berries in two vineyards located in the southwest (SW) and northeast (NE) areas of the province, starting at the beginning of veraison, was studied. Quality attributes, phenolic compounds, and aroma profiles showed significant changes during maturation. Although full maturity was reached for both Frontenac and Marquette in the SW vineyard (1380 accumulated growing degree days, based on 10 °C), the accumulation of 1035 growing degree days was not sufficient to fully ripen Frontenac and Marquette in the NE vineyard. Principal component analysis showed different ripening patterns for the two studied locations. The longer veraison in the SW vineyard resulted in higher quality attributes and higher flavor development for both Frontenac and Marquette. Under the colder conditions in the NE vineyard, metabolite accumulation was driven primarily by berry growth, and flavor development was limited. Besides growing degree days and technological parameters (total soluble solids, pH, titratable acidity), which provide significant guidelines for maturity assessment in cold climate, phenolic maturity may be followed by the accumulation of hydroxycinnamic esters and flavonoids, although the impact of these compound classes on quality remains to be determined in cold-climate wines. In both Frontenac and Marquette, aromatic maturity was best assessed using the ratio of cis-3-hexenol to trans-2-hexenal, which showed a constant decrease until maturity. Interestingly, a shift in C6 compound profile, illustrated by the progression of the sum of C6 compounds respectively produced from linoleic (C18:2; hexanal and 1-hexanol) and α-linolenic (C18:3; trans-2-hexenol and cis-3-hexenol) acids occurred during ripening, with α-linolenic acid (C18:3) degradation products decreasing in both varieties as maturation approached. At harvest, aroma profiles of both Frontenac and Marquette were dominated by C6 compounds (hexanal, trans-2-hexenal, 1-hexanol, cis-3-hexenol, and hexanoic acid), acetic acid, ß-damascenone, and 2-phenylethanol, with Marquette additionally showing significant levels of monoterpenes (linalool, geraniol, and α-citral) and 1-octen-3-ol.

Nondestructive measurement of fresh tomato lycopene content and other physicochemical characteristics using visible-NIR spectroscopy.

Measurement of fresh tomato fruit overall quality, and particularly lycopene content, is challenging in the context of high-volume production. An experiment was conducted to simultaneously measure various quality parameters of tomato in a nondestructive manner using vis-NIR reflectance spectroscopy and chemometrics. The sampling set included different cultivars that are obtainable from both retailers' shelves and two greenhouse producers. Results indicate that lycopene content was accurately predicted [r(2) = 0.98; root mean square error of cross-validation (RMSECV) = 3.15 mg/kg], along with color variables such as Hunter a (r(2) = 0.98), L, and b (r(2) = 0.92). Tomato color index (TCI) was better predicted (r(2) = 0.96) than the a/ b ratio (r(2) = 0.89). Firmness prediction, with an r(2) of 0.75, is comparable to what is reported in the literature for other fruits and may have a practical interest. Prediction of internal quality such as pH, soluble solids, titratable acidity, and electrical conductivity was less accurate, partly due to a low variability of these parameters among samples. Predictions were robust with regard to cultivars, except for pink variety tomato. The 400-1000 nm range gave results almost as accurate as the 400-1500 nm range.