Greenhouse Conditions Research Articles

Rice Brown Planthopper, Nilaparvata lugens (Stål) Feeding Behaviour in Resistant NAGINA22 Rice Mutants

Background: Rice (Oryza sativa L.), is an important staple food and an excellent source of calories in India. Of the different insect pests attacking rice, brown planthopper, BPH, Nilaparvata lugens (Stål) is an important sucking pest causing upto 100% yield losses. Host plant resistance is the most important method in keeping BPH under control and understanding the underlying mechanisms of resistance is necessary to breed the resistant varieties with desirable characters. Methods: Selected EMS mutant lines of Nagina22 (N22) variety, which were previously mass screened under controlled greenhouse conditions were assessed for their antixenosis mechanism to brown planthopper feeding by measuring probing marks and honeydew excretion area by following standard procedures and statistical analysis was done by using Statistix 8.1 software. Result: Both the brown planthopper nymphs and adults probed more in the resistant mutants compared to the susceptible mutants whereas the BPH adults probed more times (24.4) compared to the nymphs (22.2). The recorded honeydew excretion area by the resistant mutants was lower than that of susceptible mutants. In general, the BPH adults fed more and excreted more honeydew (79.5 mm2) compared to the nymphs (59.0 mm2). The damage score has a negative correlation with the probing marks of adults (-0.207) and nymphs (-0.411); and a positive correlation with honeydew excretion of adults (0.547) and nymphs (0.200). In this study, the EMS N22 mutants resistant to BPH, with a greater number of probing marks and less honeydew excretion area can serve as best donors in the breeding programmes to develop brown planthopper resistant varieties.

The influence of foliar macronutrient on growth and yield of sweet corn grown in Rengam and Rasau soil series under greenhouse conditions

The purpose of this study was to determine the effects of different rates of macronutrients as a foliar applications on growth and yield performance of sweet corn cultivated in Rengam and Rasau soil series of Malaysia under greenhouse condition. The study comprised five treatments of macronutrient fertilization as a foliar application (0, 25, 50, 75 and 100 % NPK). The plant height, stem width, leaf number, leaf area and cob height of sweet corn grown in Rengam soil series were significantly influenced by foliar macronutrient application. Notably, a rise in cob weight of sweet corns cultivated in Rasau soil series was observed at the 75 % rate, reaching 75 g, compared to 68 g for sweet corn grown in Rengam soil series. The foliar application of 100 % NPK resulted in the highest total leaf area at 252.92 cm2 compared to all other treatments. Regarding the cob fresh weight and dry matter content of sweet corn cultivated in the Rasau soil series, significant improvement noted with the 75 % NPK treatment, however plants grown in the Rengam soil series and treated with 75 % NPK as a foliar application did not exhibit significant effects. The concentrations of Fe and Mn in the corn stem from both soil series significantly increased with macronutrients foliar application. In the corn leaves grown in Rengam soil series, the concentration of nutrients was significantly influenced by the rate of NPK used as a foliar application in this study. Notably, the increased of Ca content in the treated leaves was significantly higher compared to control plants. Additionally, the contents of P, K, Cu and Zn in the corn flower of the plants in the Rengam soil series were significantly elevated in treated plants compared to untreated ones. Conclusively, based on this greenhouse study, it can be inferred that two foliar sprays of macronutrient solution at rates of 75 % and 100 % NPK greatly enhanced the growth, yield and nutrient contents of sweet corn cultivated in the Rengam and Rasau soil series.

Effectiveness of Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) on Parthenium weed (Parthenium hysterophorus) under greenhouse condition in Ethiopia

Background Parthenium is an invasive annual weed that affects crop production, rangelands, grasslands, animals, the environment, and human health. Since its introduction into Ethiopia, different management options such as uprooting, slashing, burning, plowing, and applying synthetic herbicides have been practiced. However, these options are not sustainable in weed management. However, Zygogramma bicolorata is known to be used in different countries. Although many countries use it under field conditions, its population-based efficacy has not been well studied in Ethiopia. This study aimed to determine the effectiveness of Z. bicolorata populations on parthenium plants under greenhouse conditions. Methods This experiment was conducted at the Ambo Agricultural Research Center. Different numbers of Z. bicolorata per plant were used as treatments and were laid out in a completely randomized design with three replications. The numbers of damaged leaves, eggs, and larvae were recorded daily until the leaves were completely defoliated. The collected data and the correlation between beetle population and leaf defoliation were analyzed using SAS. Results The result revealed that all beetle populations caused damage to weed plants. A higher population of beetles completely defoliated the leaves within 12 days. However, lower numbers required 21 days to completely defoliate the weed. In contrast, a higher number of eggs (328.67) and larvae (272.33) were obtained from plants that received 20 pairs of beetles. The beetle population and exposure time were positively correlated, and the effectiveness of the bioagent was greater following the emergence of larvae. Conclusions Z. bicolorata can manage parthenium weeds, even with a lower population. However, more than 15 pairs of beetles could be suggested to manage weeds in a shorter time, and further study is needed under field conditions by considering the different agroecologies of the country.

Sodium Tetraborate Induces Systemic Resistance in Watermelon against Stagonosporopsis cucurbitacearum

Imbibing watermelon seeds in 1 mM sodium tetraborate (Na2B4O7) for 24 h systemically protected plants against foliar infection by Stagonosporopsis cucurbitacearum in detached leaves and under greenhouse conditions. The treatment resulted in both a reduction in the overall percentage of leaf infection as well as in the size of lesions. Studies of the mechanisms by which Na2B4O7 protected watermelon showed that there was no direct effect on the S. cucurbitacearum mycelium growth in vitro. On the other hand, plants raised from seeds primed with Na2B4O7 showed a higher frequency of fluorescent epidermal cells compared to the plants treated with water. This indicates that a higher number of cells expressed the hypersensitive response after Na2B4O7 priming. In addition, there was an increase in peroxidase activity and an enhanced accumulation of a 45 kDa acidic peroxidase isoform during the early stages of infection in plants treated with Na2B4O7 compared to plants treated with water and this was positively correlated to the reduction of leaf infection caused by the pathogen. These results indicate that Na2B4O7 is able to induce systemic resistance in watermelon against S. cucurbitacearum by activating the hypersensitive reaction at penetration sites, increasing peroxidase activity and altering the peroxidase isozyme profile. Although each individual response may only have had a minor effect, their combined effects had a reducing effect on the disease.

Single amino acid change in tomato brown rugose fruit virus breaks virus-specific resistance in new resistant tomato cultivar

IntroductionTomato cultivation across the world is severely affected by emerging plant viruses. An effective method for protection of commercial crops against viral threats is the use of cultivars harboring resistance genes. Tomato brown rugose fruit virus (ToBRFV), a recently emerged tobamovirus, is able to overcome the dominant Tm-22 resistance that is present in the majority of commercial tomato cultivars. In an effort to alleviate the severe consequences of ToBRFV on tomato production, tomato breeding companies are developing new cultivars with varying levels of resistance against ToBRFV.MethodsIn the present study, cultivars with a new resistant phenotype against ToBRFV were screened against a wild-type isolate of ToBRFV, and subsequently, their performance under commercial greenhouse conditions was monitored. Following the identification of ToBRFV symptoms in a commercial greenhouse—where both new resistant and susceptible cultivars were interplanted—these cultivars were more closely examined.ResultsThe presence of ToBRFV was molecularly confirmed on both cultivar types suggesting that the new resistance had been broken. High-throughput sequencing (HTS) was used to study the complete genomes of viral isolates present in the two cultivar types. The analysis revealed a single amino acid change at position 82 of the movement protein of ToBRFV in the isolate present in the new resistant cultivar compared with the isolate identified in the susceptible cultivar.DiscussionA screening bioassay, that was performed to compare the infectivity of the two ToBRFV isolates, confirmed that only the isolate with this specific amino acid change could successfully infect the resistant cultivar, overcoming the new resistance against ToBRFV.

Joint Impacts of Meloidogyne incognita and Soil Nutrition on Solanum lycopersicum var. cerasiforme.

Strategies for plant nutrient resource allocation under Meloidogyne spp. infection and different soil nutrient conditions are not well established. In response, the objectives of this research are to determine if increased vegetative growth of Solanum lycopersicon var. cerasiforme (cherry tomato) under high nutrition enhances resistance to M. incognita and whether adaptive strategies for growth, reproduction, and nutrient uptake by cherry tomato infected with M. incognita alter nutrient availability. The study was conducted under greenhouse conditions using high, medium, and low soil nutrient regimes. The research results indicate that the total biomass of cherry tomato was less in the presence of M. incognita infection under all three nutrient conditions, compared with plants grown in the absence of this nematode. However, the increase in the root/shoot ratio indicates that cherry tomato allocated more resources to belowground organs. Under the combined impacts of M. incognita infection and low or medium soil nutrition, the nitrogen content in root system tissues and the phosphorus content in shoot system tissues were increased to meet the nutrient requirements of galled root tissue and plant fruit production. It is suggested that plants increase the allocation of reproductive resources to fruits by improving phosphorus transportation to the aboveground reproductive tissues under low and medium nutrient conditions. Overall, the study highlights a significant impact of soil nutrient levels on the growth and resource allocation associated with M. incognita-infected cherry tomato. In response, soil nutrient management is another practice for reducing the impacts of plant-parasitic nematodes on crop production.

Potential Role of the Yeast Papiliotrema terrestris Strain PT22AV in the Management of the Root-Knot Nematode Meloidogyne incognita

Potential Role of the Yeast Papiliotrema terrestris Strain PT22AV in the Management of the Root-Knot Nematode Meloidogyne incognita

Evaluation of the effect of organic fertilizers on the morphophysiological parameters and antioxidant compounds of Swiss chard (Beta vulgaris L.).

Objective: To evaluate the effect of organic fertilizers on the morphophysiological parameters and antioxidant compounds of Swiss chard (B. vulgaris L.) var. ‘Rainbow’ grown under greenhouse conditions. Design/Methodology/Approach: A completely randomized design was used with three treatments and 33 repetitions: T1 (poultry manure-based organic fertilizer (T1 AAC)), T2 (coffe pulp-based vermicompost (T2 LC)), and T3 (chemical fertilization (T3 FQ)). Plant height, stem diameter, number of leaves, leaf area, fresh biomass, dry biomass, chlorophyll A, chlorophyll B, total chlorophyll, carotenoids, total polyphenols, DPPH, and yield were evaluated. An analysis of variance and Tukey’s test (α=0.05) were used. Results: For most of the variables evaluated, the best results were obtained with the poultry manure-based organic fertilizer (T1 AAC) treatment. The antioxidant compounds and the quality of Swiss chard were influenced by organic fertilizers, with 0.21 mg Eq. gallic acid g-1 fresh tissue (ft), total chlorophyll of 19.5 µg g-1 (ft), and a yield of 6,150 kg·m2. Study Limitations/Implications: The mineral content of this vegetable was not evaluated. Findings/Conclusions: The use of poultry manure-based organic fertilizers can be an alternative nutritional management for Swiss chard cultivation.

Seed coating with minerals and plant growth-promoting bacteria enhances drought tolerance in fennel (Foeniculum vulgare L.)

The seeds of many plants, including fennel (Foeniculum vulgare L.), are tiny and have low food reserves. Therefore, planting them accurately in the soil to achieve optimal yields is challenging. The present research aimed to study the impact of bio-priming and seed coating on seedling and vegetative growth of fennel plants under drought stress. The experiments were conducted in laboratory and greenhouse conditions triplicate using a completely randomized design (CRD). These experiments applied mineral and biological coating treatments as the first factor and drought tolerance at three levels (0, −0.3, and −0.6 MPa) as the second factor. Perlite (P), Vermiculite (V), and Kaolin (K) were used as a mineral coating. The mineral coating mixture was P10V10K5. The numbers mean the material (gr) ratio based on the seed weight. Combinational treatments of seed coating were CHA0 + coating, PF56 + coating, T39 + coating, T36 + coating, and non-coating (as control). Pseudomonas fluorescens P.F56, P. fluorescens CHA0, and Trichoderma harzianum T36 and T. harzianum T39 were employed as biological treatments. Experimental results showed that at 0 and -0.3 MPa osmotic potential levels, the T39 + coated seeds had the highest percentage of seedling emergences. At the −0.3 MPa level, the T39 + coated seeds had an increased seedling emergence percentage by 24% compared to un-inoculated seeds. At all levels of drought stress, the CHA0 + coated treatment had the highest level of chlorophyll a content, CAT, and APX enzyme activity. Seed coating with CHA0 and T39 enhanced fennel's early vegetative growth and biochemical characteristics under normal and drought stress and mitigated drought stress.

Effect of Fungicides and Application Intervals for the Control of Black Spot of Roses

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.

Endophytic bacteria nano-formula: A promotor for plant growth and systemic acquired resistance against sheath blight disease on rice

Sheath blight disease significantly affected growing rice crop and caused yield losses. This study identified two endophyte bacterial isolates, Bacillus subtilis, and Pseudomonas brassicacearum subsp. Neoaurantiaca, significantly inhibit Rhizoctonia solani AG1 IA mycelial growth. Further, the analysis of the culture filtrate for the two identified bacteria recorded a set of bioactive components that have antifungal activity and enhance plant growth. We prepared a novel nano-formula using the advantages of nano natural charcoal (NCNPs) as an organic matter and enriched with alginate to improve the nano-formula porosity and keep the viability of the loaded bacteria up to 18 months. Two methods (soil application and root dipping) were used to evaluate the impact of bacteria nano-formula on rice growth and rice sheath blight (ShB) disease under artificial inoculation with R. solani at greenhouse conditions. The root dipping with P. brassicacearum NCNPs alginate (PBNF-R) and B. subtillus NCNPs alginate (BSNF-R) recorded the highest performance in the rice growth traits, and a high control level of the rice ShB disease by decreasing relative lesion height and percent disease index. In addition, PBNF-R and BSNF-R increase the defense-related enzyme production in the plant cell (peroxidase, polyphenol oxidase, and phenylalanine ammonia‐lyase) and, consequently, the plant immunity. Moreover, both upregulate the gene expression levels of OsNPR1, OsWRKY45, OsPR10, and OsAOS2, which are related to the plant defense mechanism. Finally, here we introduce the first application of bacteria nano-formula as a safe environmental approach to control the rice ShB disease, promoting growth and thousand-grain weight in rice.

Tolerância à salinidade e respostas espectrais foliares em mudas de quatro espécies ornamentais herbáceas

ABSTRACT Studies on using brackish water for the irrigation of ornamental species are still scarce, mainly considering qualitative aspects of the plants. Therefore, the present study aimed to identify salt tolerance and characterize leaf spectral responses of herbaceous ornamental species at the stage of commercial seedling production. The research was carried out from December 2020 to February 2021, under greenhouse conditions, in Fortaleza - Ceará, Brazil. The experiment was conducted in a randomized block design with split plots, with main plots consisting of irrigation-water salinity levels (0.5, 2.0, 4.0, 6.0, and 8.0 dS m-1), and subplots by the species Catharanthus roseus, Celosia cristata, Celosia plumosa, and Chrysanthemum coronarium, with four replications. The evaluation parameters were dry mass production, visual sensory analysis, salt tolerance, and leaf spectral responses. Plant visual quality was maintained up to 2.0 dS m-1 for Chrysanthemum coronarium and 4.0 dS m-1 for Celosia cristata, Celosia plumosa, and Catharanthus roseus, which were classified as moderately tolerant at those respective salinity levels. Salinity caused noticeable changes in leaf spectral responses, especially in the visible region.

Phenotypic Evaluation of a Lemon Hybrid Population to Identify Sources of Resistance to Plenodomus tracheiphilus

Mal secco, caused by the fungus Plenodomus tracheiphilus, is a xylem disease that is a limiting factor for lemon production in the Mediterranean. Resistance or field tolerance are major goals for lemon breeders; however, there is scant information regarding the heritability of mal secco resistance in breeding populations. As with other vascular diseases, phenotyping is the bottleneck for ascertaining resistance and susceptibility, and a validated protocol for greenhouse phenotyping would be valuable to accelerate the selection of tolerant trees before field evaluation. We report phenotyping of 148 hybrids of Khasi papeda (Citrus latipes; tolerant to mal secco) × lemon (susceptible to the disease) in field and greenhouse conditions. Field evaluation was performed on all hybrids for 2 to 3 consecutive years on trees subjected to high natural-pathogen pressure. Detection of the fungal infection was performed by visual observation and real-time polymerase chain reaction (PCR). The first infections occurred ≈6 months after planting, but 2 years of observations were needed for a reliable estimation of susceptibility. The spread of the disease did not occur uniformly throughout the plot, with patterns of spread within rows, probably resulting from infections from plant to plant. The possible errors in the estimation of susceptibility as a result of the uneven distribution of infections in the plot were reduced by using more than one replicate tree per hybrid. The correlation between phenotyping scores and cycle threshold values was weak (r = –0.48, P < 0.001). Three years after planting, hybrids clustered into three groups—susceptible, tolerant, and intermediate—based on symptom progression. A subset of 65 self-rooted hybrids was also subjected to stem inoculation in an unheated greenhouse, with two to seven biological replicates per hybrid. Three months after inoculation, the samples were monitored for symptoms appearance and subjected to real-time PCR pathogen quantification. We observed a weak (r = 0.41) but significant (P < 0.001) correlation between phenotypes in the field and the greenhouse, indicating that, in our conditions, field evaluation remains the best method for phenotyping. However, artificial inoculations might help to discard the highly susceptible hybrids before field evaluation.

Root System Reductions of Grafted ‘Valencia’ Orange Trees Are More Extensive Than Aboveground Reductions after Natural Infection with Candidatus Liberibacter Asiaticus

Huanglongbing (HLB), which is associated with the phloem-limited bacteria Candidatus Liberibacter asiaticus (CLas), is a devastating disease that affects citrus trees worldwide. Because of the pervasiveness of the bacteria and psyllid vector, the disease is considered endemic in Florida. Although the effects of CLas on tree growth and physiology have been investigated for decades, most studies compared infected and noninfected trees under greenhouse conditions. This study used newly planted field-grown ‘Valencia’ sweet orange (Citrus sinensis) trees on two different rootstocks to monitor the distribution and accumulation of CLas in aboveground and belowground tissues following natural psyllid colonization and assess tree physiological responses and biomass reductions under HLB-endemic conditions. Trees were transplanted into the field with individual protective covers (IPCs), which are used to exclude psyllids and prevent infection. Openings were cut in the IPCs of half of the trees; to promote infection, these IPCs were temporarily removed during the main vegetative flushing period when psyllid populations were high. All trees that were exposed to psyllids became infected and displayed the symptoms typically associated with HLB. Throughout the study, higher levels of CLas were detected in the leaves compared with those in the fibrous roots. Trees that were not exposed to psyllids remained noninfected and healthy. After 18 months, a subset of trees was excavated to assess biomass differences between infected and noninfected trees. Infected trees had root system reductions of 37% and shoot system reductions of 20%, thereby significantly reducing the belowground-to-aboveground biomass ratio. Fibrous root loss was 49% and more severe than the loss of the rest of the root tissue. This study is the first to demonstrate the full extent of damage caused by CLas infection under natural HLB-endemic conditions. The results confirm previous observations that suggested fibrous root loss as one of the major consequences of infection and colonization with CLas. They also reinforce the benefits of using IPCs to prevent infection of young citrus trees during the first years of growth in the field.

Impact of microbial consortium of Rhizobium tropici and Rhizobium mayense on the growth of Phaseolus vulgaris L.

The main objectives of the present investigation was to characterize and recognize potential indigenous Rhizobium spp. associated with red clover nodules, as well as to evaluate the influence of prospective rhizobia inoculation (individual and consortia) on common bean plant growth. Total of 8 rhizobia like bacteria were isolated and were investigated for their specific PGP traits, production of hydrolytic enzymes. Results revealed, four isolates synthesize IAA (22.3 ± 1.45 to 88.6 ± 1.45 μg mL−1), three isolates solubilized phosphate (40.69 ± 1.25 to 216.3 ± 1.31 μg mL−1), three isolates solubilized potassium, produced siderophore, and showed chitinase production, two isolates possess ACC deaminase activity, one isolate was able to solubilize zinc, 5 isolates produced β- 1, 3-glucanase (0.38 ± 0.005 to 2.82 ± 0.011 % units) and four isolates produced cellulase. Two bacterial isolates found to exhibit most of the PGP activities, were selected and identified on the basis of phenotypic, biochemical tests and 16S rRNA sequencing, as Rhizobium tropici IHTF-1 and Rhizobium mayense IHTF-2. Interaction of these potential rhizobium strains individually and consortia with common bean plants under greenhouse conditions boosted root and shoot length, fresh and dry biomass compared to un-inoculated control plants. SEM study revealed that both the strains, IHTF-1 and IHTF-2 colonized common bean roots. These results imply that Rhizobium spp., identified in this work, can be used as bio-inoculants to increase common bean plant production in a sustainable way.

Morphological and Physiological Responses of Two Penstemon Species to Saline Water Irrigation

Penstemon, with more than 250 species native to North America, holds significant aesthetic and ecological value in Utah, supporting diverse pollinators. Despite their significance, the survival of penstemon is threatened by challenges such as habitat loss, climate change, and Utah’s naturally high soil salinity. To address these challenges and understand their adaptability, this study evaluated the salt tolerance of two penstemon species [Penstemon davidsonii (Davidson’s penstemon) and Penstemon heterophyllus (foothill penstemon)] under controlled greenhouse conditions. The aim was to develop baseline information for nursery production and landscape use that utilize reclaimed water for irrigation. Plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.0 dS·m−1 as control or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 for 8 weeks. Half of the plants were harvested after four irrigation events, and the remaining plants were harvested after eight irrigation events. At harvest, visual rating (0 = dead and 5 = excellent without foliage salt damage), plant width, number of shoots, leaf area, shoot dry weight, leaf greenness [Soil Plant Analysis Development (SPAD)], stomatal conductance, and canopy temperature were collected to assess the impact of salinity stress. In both species, salt damage was dependent on the salinity levels and length of exposure. After four irrigation events, both species exhibited foliage damage that increased in severity with rising EC. The most severe damage was observed in plants receiving saline solution at an EC of 10.0 dS·m−1. After eight irrigation events, P. davidsonii exposed to a saline solution with an EC of 10.0 dS·m−1 received a visual rating of 0, whereas P. heterophyllus had a visual rating of 0.4. Both species exhibited salinity-induced effects, with variations observed in the specific parameters and the degree of response. Penstemon davidsonii exhibited significant salinity stress, as indicated by reduced leaf area, shoot dry weight, SPAD reading, and stomatal conductance with increasing EC of the saline solution. In addition, in both species, at both harvests, canopy temperatures increased either linearly or quadratically by 8% to 36% as the EC levels of the saline solution increased. These results indicate that P. davidsonii was more sensitive to salinity stress than P. heterophyllus.

Are predatory mites effective as biological control agents to suppress Oligonychus ilicis (Acari: Tetranychidae) in blueberry plantings?

Southern red mite, Oligonychus ilicis McGregor (Acari: Tetranychidae), is an important polyphagous spider mite pest that causes economic damage to many ornamentals, coffee, and fruit crops. Blueberry growers in the Southeastern United States, including Florida and Georgia, have experienced severe losses due to outbreaks of O. ilicis. Predatory mites are an important management tool used for controlling spider mites; however, predators have not been studied and successfully evaluated in blueberry systems. Amblyseius swirskii Athias-Henriot, Phytoseiulus persimilis Athias-Henriot, and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) are among the most economically important arthropod agents used in augmentative biological control worldwide. To evaluate the potential of these 3 commercially available predatory mites for use in blueberry plantings, we conducted experiments under controlled laboratory conditions and in the greenhouse. In preliminary laboratory experiments, P. persimilis and N. californicus significantly reduced the number of O. ilicis motile stages below those found in the untreated control, indicating the potential for these 2 predatory mite species to suppress O. ilicis populations. Amblyseius swirskii did not perform well controlling O. ilicis motiles in the laboratory. Under greenhouse conditions, N. californicus and P. persimilis significantly reduced the number of eggs after 7 days of release and the number of motile stages after 14 days of release. This is the first report of using phytoseiid mites to suppress O. ilicis in blueberry systems in the United States. Further studies on predator behavior, feeding preferences, and acaricide compatibility with predators are required to investigate the possibility of using P. persimilis, and N. californicus as biological control agents of O. ilicis in blueberry systems.

Ecological intensification strategies increase abundance of denitrifying functional genes in a greenhouse agricultural soil

Understanding the denitrification process in agriculture is key to preventing nitrogen (N) losses and reducing emissions of the greenhouse gas nitrous oxide (N2O) to the atmosphere. Since the type of fertilization influences this process, in this study we evaluated the comparative effect of conventional (CON) versus ecological intensification (EI) soil management under greenhouse conditions on the abundance and expression of the denitrifying functional genes nitrite reductase (nirK, nirS) and nitrous oxide reductase (nosZ). For this purpose, quantitative PCR (qPCR) was performed in three phenological stages of eggplant (Solanum melongena L var. Telma). The results showed that the addition of organic amendments tripled the copies of nirK DNA, doubled the copies of nosZ DNA and increased the copies of nirS, albeit by 2 %, compared to conventionally managed soils. The abundance of mRNA transcripts also increased for all three genes studied: nirK increased 15-fold, followed by nirS, which tripled its expression, and nosZ, which doubled its expression. Ammonium ion (NH4-N) correlated positively with the three genes analyzed, total organic carbon (TOC) with nirK and nosZ, and pH correlated negatively with nirK and nosZ. Regardless of the type of fertilization (CON or EI), a decreasing trend in gene abundance was observed from the initial growth phase of the crop (t0) until the crop was removed and crop residues incorporated into the soil (t2). The results suggest that the dynamics and composition of the denitrifying community varied in response to the type of fertilization and the phenological stage of the crop. Further studies based on metagenomics and transcriptomics, including N2O flux measurements, are needed to better understand the denitrification process in these soils.

Effect of Biochar on Soil Fertility Change on Sandy Loam Soil and Clay Soil Under Greenhouse Condition

Biochar derived from agricultural residue can be used for soil improvement to enhance soil fertility and soil chemical, physical and biological properties. The objective of this research was to study the effects of biochar on soil fertility of sandy loam soil and clay soil in greenhouse condition. Treatments were laid out in 2x5 Factorial in RCB with four replicates. The first factor was two soil types: 1) Clay soil (Cl) and 2) Sandy loam soil (SL). The second factor was five biochar (BC) rates: 0 16 32 48 and 64 g/10 kg soil (equaling to 0.5, 1.0, 1.5 and 2.0 ton/rai). In each treatment; nitrogen, phosphate and potash fertilizers were applied (based on soil analysis). The results showed that the addition of biochar to clay soil increased available soil nutrient and total nutrient uptake in plant higher than (p<0.01) sandy loam soil. Biochar application to clay soil significantly increased growth and dry matter of maize (p<0.01). The addition of biochar also showed a tendency to increase soil organic matter and exchangeable potassium in clay soil higher than in sandy loam soil (p<0.01). However, available phosphorus in clay soil was lower than sandy loam soil. Moreover, it was found that the soil-biochar application in both soils types increased nitrate retention greater than the soil without biochar. The results of this study indicated that biochar can be used to increase the fertility of the clay soil at the rate of 1.5 tons/rai.

The Effects of Different GA3 and Mycorrhiza Dosages on Mini Tuber Production in Potatoes

This study was conducted in 2017 under greenhouse conditions using selected four different potato clones to determine the effects of different doses of GA3 and arbuscular mycorrhizal fungus on mini tuber production. The research, carried out in a randomized complete block design with three replications, applied GA3 doses of 0, 5, 10, and 15 ppm, and mycorrhizal inoculat doses of 0, 500, 1250, and 2000 mg/100 tubers. Parameters including emergence time, plant height, main stem number, tuber number, average tuber weight, tuber size distribution (>45 mm, 28-45 mm, <28 mm), and maturity period were examined. The effect of GA3 application on all investigated parameters except the number of main stems was significant, statistically. The highest mini tuber number (9.1 tubers) and mini tuber yield (408.4 g/pot) were obtained from the application of 15 ppm GA3, while the highest average mini tuber weight (46.74 g) was obtained from the control group. In mycorrhizal applications, the highest tuber number was obtained at a dose of 500 mg/100 tubers, and the highest mini tuber weight and yield were obtained at a dose of 1250 mg/100 tubers. As a result of the study, it was determined that the application of 15 ppm GA3 is suitable due to its positive effect on mini tuber multiplication, and the mycorrhizal application at a dose of 500 mg/100 tubers is appropriate due to its positive effect on increase of tuber number.