Control Of Soil-borne Diseases Research Articles

The combination of seed treatment and cultivar selection is effective for control of soilborne diseases in chickpea

Damping-off and root rot are diseases of concern in chickpea (Cicer arietinum L.) production and can cause seedling loss, increase weed populations, and reduce yield. A complex of soilborne pathogens is responsible for damping-off and root rot in the Northern Great Plains. Species within this complex include Fusarium spp., Pythium spp., and Rhizoctonia solani. Currently, partially resistant cultivars and fungicide seed treatments are the most effective for control of damping-off and root rot. This study examined 25 chickpea cultivars and breeding lines with and without a fungicide seed treatment (fluxapyroxad, pyraclostrobin, and metalaxyl) for stand establishment and grain yield in field conditions. Experimental plots were located in dryland and irrigated fields at the Eastern Agriculture Research Center (EARC) in Sidney MT in 2020 and 2021, respectively. Stand counts were recorded three times to calculate area under disease progress curve (AUDPC). Yield, and protein content (only in 2021) was assessed after harvest. In 2021, pathogens were isolated from chickpea roots showing signs of root rot and identified as Fusarium solani. The results showed that the seed treatments effectively decreased soilborne disease development (75%–84%) and improved chickpea yield (11%–14%) in 2020 and 2021, and increased protein content (0.6%) in 2021. Different cultivars did not have a consistent impact on disease development and yield protection. NDC160166 and NDC160236 displayed consistently lower disease and higher yield and might be a future source of disease resistance. Yield of untreated seeds decreased and AUDPC increased for all cultivars/lines in both years. A negative correlation was also observed between protein content and chickpea yield in 2021.

Mechanism of the antifungal action of chloropicrin fumigation against Panax notoginseng root rot caused by Fusarium solani

Fusarium root rot caused by Fusarium solani severely damages the roots of Panax notoginseng (ginseng) seedlings eventually leading in most cases to the total loss of this valuable crop. Soil fumigants are generally better at controlling soil-borne diseases such as F. solani than fungicides which provide unacceptable control. Therefore, this study aimed at evaluating the efficacy of fumigant chloropicrin (Pic) against F. solani in both laboratory and field. Ultrastructural changes in the mycelia of F. solani in each treatment were indicative of structural changes at the cellular level by transmission electron microscopy (TEM). Bacterial and fungal communities and diversity were targeted for Illumina high-throughput sequencing. Results indicated that chloropicrin inhibited F. solani mycelial growth completely at a concentration of 1.2 μg/l. In addition, ultrastructural studies showed that Pic caused plasmolysis and plasma leakage, indicating that the cell membrane of F. solani was disrupted. In the field trials, Pic at 45 g/m2 yielded an excellent long-term control of target pathogens, and treated plots allowed P. notoginseng plants to maintain vigorous growth compared with the untreated controls. Illumina MiSeq sequencing results revealed that bacterial communities were affected more seriously by Pic than fungi. The beneficial microbes (such as Trichoderma and Chaetomium) gradually increased, and the harmful microbes (such as Fusarium) decreased in fumigated soil. Together, the promotion of beneficial microorganisms and the direct inhibition of F. solani by chloropicrin were the main mechanisms for the prevention and control of soil-borne diseases. Our results provide useful information understanding chloropicrin fumigation against soil-borne disease.

Compost Based Bio-pesticide to Control the White Root Disease caused by Rigidoporus microporus of Rubber Growing Lands in Sri Lanka

White root disease caused by Rigidoporus microporus is the most destructive root disease in rubber plantations of Sri Lanka. Trichoderma is a useful, filamentous fungus, widely used as bio-control agents for controlling soil borne diseases of plants and as growth promoters. An attempt was taken to use a compost based bio-pesticide as environmental friendly and low cost substitution against R. microporus. Soil samples were collected from different rubber growing districts and antagonistic fungi were selected using dual plate culture test. Among the antagonistic fungi, the best performing two isolates, which showed more than 80% inhibition against R. microporus were identified. The two fungi were used for the production of the bio-pesticide. Fungi were inoculated in to compost media (7.5-7.8 log10CFUg-1 ) and shelf life time was monitored. The effectiveness of the media under field conditions was evaluated using a pot trial. The results of the study revealed that in compost based media, the most effective fungus was proven to be T. harzianum. Compost based formulations of Trichoderma have shelf life of 8 months. As the nutrient content of the compost medium is high, an increment of the CFUg-1 was observed within the first six weeks. The reduction of the nutrient content and production of toxic metabolites due to the high population could be the reason for the gradual decrease of CFUg-1 after ten weeks. The pot trial carried out using the compost based biopesticide gave promising results. Based on the results, handling convenience, additional nutrition of medium etc., compost based bio-pesticide has been identified as successful in the prevention of white root disease in rubber plants.

Termite Nest Associated Bacillus siamensis YC-9 Mediated Biocontrol of Fusarium oxysporum f. sp. cucumerinum.

The antagonistic potential of bacteria obtained from the nest of Odontotermes formosanus was assessed against Fusarium oxysporum f. sp. cucumerinum (FOC). Of 30, seven termite nest-associated bacteria strains had biocontrol potential. Among them, the strain YC-9 showed the strongest antifungal activity toward FOC. Phylogenetic analysis of the 16S rRNA amplified product of YC-9 revealed its identification as Bacillus siamensis. The in vivo antifungal activity experiment showed that the application of YC-9 at 108 cfu/ml significantly reduced the cucumber wilt incidence with a control efficacy of 73.2%. Furthermore, plant growth parameters such as fresh weight, dry weight, plant height, and root height were significantly improved by 42.6, 53.0, 20.8, and 19.3%, respectively. We found that inoculation with B. siamensis YC-9 significantly increased the activity of defensive enzymes such as peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) in diseased cucumber roots, thereby raising the resistance. PCR using gene-specific primers revealed that B. siamensis YC-9 contains biosynthetic genes for known antibiotics, including bacillomycin, iturin, and surfactin. Chemical analysis of the cultivation of B. siamensis YC-9 resulted in the isolation of five metabolites, including hexadecanoic acid (1), cyclo-(L-phenylalanylglycine) (2), cyclo-(L-trans-Hyp-L-Leu) (3), C15-surfactin (4), and macrolactin A (5), the structures of which were identified by the analysis of NMR spectroscopic data and MS. Among them, the compound 4 showed significant antifungal activity against conidial germination of FOC with an IC50 value of 5.1 μg/ml, which was comparable to that of the positive control, cycloheximide (IC50 value of 2.6 μg/ml). Based on these findings, this study suggests that termite-nest associated B. siamensis YC-9 could be a potential biological control agent for integrated control of soil-borne diseases like cucumber Fusarium wilt.

Efficiency of calcium cyanamide on the control of tomato soil-borne disease and their impacts on the soil microbial community

Soil-borne diseases resulting from continuous cropping are a huge problem for tomato producers around the world. In this study, differences in the efficiency of soil-borne disease control and the impact on the soil microbial community were investigated between two types of soil fumigation treatments, namely calcium cyanamide (CaCN2) and soil solarization with flooding (SS-F). Soil samples were taken at 0 days after transplantation (DAT), 60 DAT, 150 DAT and 220 DAT during the tomato season. The composition of microbiome after soil fumigation was assessed using heterotrophic plate counts, PCR and MiSeq high-throughput sequencing. CaCN2 and SS-F fumigation significantly reduced the disease incidences, at 4.98% and 11.41%, respectively, while the disease incidence of the CK was 26.62%. In addition, CaCN2 treatment significantly improved the tomato production by 21.65% compared to CK. Under CaCN2 fumigation, the soil microbial community was temporarily inhibited from 0 DAT to 60 DAT, while the bacterial and actinomycete communities recovered at 220 DAT. Remarkably, some potential beneficial microbial genera, e.g., Proteobacteria, Zygomycota phyla, Bradyrhizobium, Arthrobacter, Bacillus, Clostridium, Kaistobacter, Streptomyces, Gemmatimonadetes, and Mortierella, increased at 220 DAT after CaCN2 application. Nevertheless, the pathogenic Acremonium, Alternaria, Fusarium, Penicillium and Verticillium were significantly decreased. However, following SS-F fumigation, the relative abundance of non-soil-borne pathogenic Acremonium and Alternaria increased by 294.27% and 189.77%, respectively, compared to that in the CK. While the ratio of potential beneficial Trichoderma decreased, the bacterial composition of the SS-F soil at 220 DAT was nearly identical to that of the CK. In addition, a redundancy analysis showed that CaCN2 treatment increased the potential of hydrogen (pH) and the organic matter (OM), available phosphorus (AP), and available potassium (AK) contents, which were positively correlated with Bradyrhizobium, Rhodanobacter, Bacillus and Mycobacterium communities and negatively correlated with disease incidence. In conclusion, CaCN2 enhanced soil fertility, reduced the presence of soil pathogens, increased the relative abundance of potential beneficial bacteria and fungi and improved tomato yields.

Subversion of Phytomyxae Cell Communication With Surrounding Environment to Control Soilborne Diseases; A Case Study of Cytosolic Ca2+ Signal Disruption in Zoospores of Spongospora subterranea.

Ca2+ signaling regulates physiological processes including chemotaxis in eukaryotes and prokaryotes. Its inhibition has formed the basis for control of human disease but remains largely unexplored for plant disease. This study investigated the role of Ca2+ signaling on motility and chemotaxis of Spongospora subterranea zoospores, responsible for root infections leading to potato root and tuber disease. Cytosolic Ca2+ flux inhibition with Ca2+ antagonists were found to alter zoospore swimming patterns and constrain zoospore chemotaxis, root attachment and zoosporangia infection. LaCl3 and GdCl3, both Ca2+ channel blockers, at concentrations ≥ 50 μM showed complete inhibition of zoospore chemotaxis, root attachment and zoosporangia root infection. The Ca2+ chelator EGTA, showed efficient chemotaxis inhibition but had relatively less effect on root attachment. Conversely the calmodulin antagonist trifluoperazine had lesser effect on zoospore chemotaxis but showed strong inhibition of zoospore root attachment. Amiloride hydrochloride had a significant inhibitory effect on chemotaxis, root attachment, and zoosporangia root infection with dose rates ≥ 150 μM. As expected, zoospore attachment was directly associated with root infection and zoosporangia development. These results highlight the fundamental role of Ca2+ signaling in zoospore chemotaxis and disease establishment. Their efficient interruption may provide durable and practical control of Phytomyxea soilborne diseases in the field.

Composition and characteristics of soil microbial communities in cotton fields with different incidences of Verticillium wilt

ABSTRACT Soil microorganisms could affect the growth of plants and play an important role in indicating the change of soil environment. Cotton Verticillium wilt is a serious soil borne disease. This study aimed to analyze the community characteristics of soil microorganisms in cotton fields with different incidences of Verticillium wilt, so as to provide theoretical guidance for the prevention and control of soil borne diseases of cotton. Through the analysis of soil microbial communities in six fields, the results showed that there was no difference in fungal and bacterial alpha-diversity index before cotton planting, while there were differences in rhizosphere of diseased plants. For fungal beta diversity indexes, there were significant differences in these six fields. There was no significant difference for bacterial beta diversity indexes before cotton planting, while there was a certain difference in the rhizosphere of diseased cotton plants. The composition of fungi and bacteria in different fields was roughly the same at the genus level, but the abundances of the same genus varied greatly between different fields. Before cotton planting, there were 61 fungi (genera) and 126 bacteria (genera) with different abundances in the six fields. Pseudomonas, Sphingomonas and Burkholderia had higher abundances in the fields with less incidence. This study will provide a theoretical basis for microbial control of Cotton Verticillium wilt.

PH-Responsive On-Demand Alkaloids Release from Core-Shell ZnO@ZIF-8 Nanosphere for Synergistic Control of Bacterial Wilt Disease.

Developing an effective and safe technology to control severe bacterial diseases in agriculture has attracted significant attention. Here, ZnO nanosphere and ZIF-8 are employed as core and shell, respectively, and then a pH-responsive core-shell nanocarrier (ZnO-Z) was prepared by in situ crystal growth strategy. The bactericide berberine (Ber) was further loaded to form Ber-loaded ZnO-Z (Ber@ZnO-Z) for control of tomato bacterial wilt disease. Results demonstrated that Ber@ZnO-Z could release Ber rapidly in an acidic environment, which corresponded to the pH of the soil where the tomato bacterial wilt disease often outbreak. In vitro experiments showed that the antibacterial activity of Ber@ZnO-Z was about 4.5 times and 1.8 times higher than that of Ber and ZnO-Z, respectively. It was because Ber@ZnO-Z could induce ROS generation, resulting in DNA damage, cytoplasm leakage, and membrane permeability changes so the released Ber without penetrability more easily penetrated the bacteria to achieve an efficient synergistic bactericidal effect with ZnO-Z carriers after combining with DNA. Pot experiments also showed that Ber@ZnO-Z significantly reduced disease severity with a wilt index of 45.8% on day 14 after inoculation, compared to 94.4% for the commercial berberine aqueous solution. More importantly, ZnO-Z carriers did not accumulate in aboveground parts of plants and did not affect plant growth in a short period. This work provides guidance for the effective control of soil-borne bacterial diseases and the development of sustainable agriculture.

The Combination of Seed Treatment and Cultivar Selection is Effective for Control of Soilborne Diseases in Chickpea

The Combination of Seed Treatment and Cultivar Selection is Effective for Control of Soilborne Diseases in Chickpea

Deciphering the Fusarium-wilt control effect and succession driver of microbial communities managed under low-temperature conditions

The regulation of microbial communities is an important strategy to control the spread of soil-borne diseases. However, the control of soil-borne diseases through the regulation of microbial communities at low-temperature conditions, and the association of their succession with abiotic factors during plant cultivation are not well characterised. In this study, the effects of various soil-disinfestation strategies, i.e. soil irrigated to saturation (SA), reductive soil disinfestation (RSD) and ammonia fumigation (AF), on the prevention of watermelon Fusarium wilt as well as the interaction of microbial community succession and abiotic factors were determined. The abundance of F. oxysporum in soil samples subjected to SA, RSD and AF treatments decreased significantly by 86.09%, 90.67% and 93.68%, respectively, compared with the untreated soil sample. RSD and AF treatments established significantly different microbial α- and β-diversities and physicochemical properties, whereas SA treatment showed no significant effect on these properties. After planting, RSD- and AF-treated soils exhibited significantly reduced disease incidence and increased the watermelon yield, respectively, whereas SA-treated soil showed no significant effects. The physicochemical and microbial characteristics of treated soils were similar to those of untreated diseased soil. Moreover, the differences in soil physicochemical characteristics remarkably and positively correlated with the dissimilarities in microbial communities. For the differences in bacterial and fungal β-diversities, soil pH was determined to have the highest mean predictor importance value. Potentially beneficial microbes were identified mainly after RSD and AF treatments; however, the relative abundances of these microbes were closely associated with soil pH and significantly decreased after planting. Overall, the soil-borne pathogens reduced and microbial community improved by RSD and AF treatments at low-temperature conditions could effectively control soil-borne diseases. Soil pH plays a pivotal role in restoring the microbial community during watermelon cultivation.

Machine learning applied to canopy hyperspectral image data to support biological control of soil-borne fungal diseases in baby leaf vegetables

Baby leaf vegetables constitute a significant segment of the convenience fresh food market. Due to cultivation conditions under plastic tunnels favourable to pathogen and to restrictions about synthetic fungicide applications, these crops are prone to soil-borne diseases and need effective biological management. Real-time tracking by digital means of the performances of antagonistic agents against plant pathogens may be a great opportunity to optimize field practices and increase disease biocontrol efficacy. In this study, a non-linear machine learning approach, based on Artificial Neural Networks technique, was used to assess the biocontrol efficacy of Trichoderma spp. from VIS-NIR spectral reflectance, estimating disease severity in baby leaf young plants during specific plant-pathogen-antagonist interactions. The most successful accurate model architecture achieved a predictive success rate of 74%. The variable impact analysis on the 207 variables considered showed that the 20 most important frequencies lie in the intervals Δω1 = [426,460] nm Δω2 = [495,530] nm Δω3 = [570,667] nm Δω4 = [770,880] nm Δω5 = [940,1000] nm. The model with improved classification accuracy is highly suitable for the automated detection of healthy status considering a wide spectrum of crop/pathogen targets under Trichoderma spp. beneficial dealings. Findings indicate that hyperspectral image-derived features could be used as proxy for disease level tracking under biological control of telluric pathogens in baby leaf vegetable cultivations.

Prevention and control of nematodes and soil borne diseases by grafting peppers

Prevention and control of nematodes and soil borne diseases by grafting peppers

Efficacy and economics evaluation of seed rhizome treatment combined with preplant soil fumigation on ginger soilborne disease, plant growth, and yield promotion.

Ginger (Zingiber officinale Roscoe) is widely planted around the world. Owing to continuous planting, ginger is seriously affected by soilborne fungi, bacteria, and nematodes. Although preplant soil fumigation is an effective prevention strategy of soilborne diseases, individual fumigant and technology could not provide effective control of ginger soilborne disease. In our research, different combinations of soil fumigants and seed rhizome treatments were evaluated by monitoring the soil pathogens population, ginger growth, yield, and estimation of economic benefits. Soil fumigation effectively reduced the population of soilborne pathogens, and chloropicrin had a better control effect on soilborne pathogens than dazomet did. Preplant soil fumigation and seed rhizome treatment not only provide good control of soilborne disease, but also reduced the incidence of plant foliar pest and disease. Average yield increase rate of seed rhizome treatment was 12.0%; the highest yield increase was 24.4%. The average cost of seed rhizome treatment only increased by about 2.86%, but the rate of net revenue increase for the seed rhizome treatment reached up to 19.1%. Seed rhizome treatment is a very cost-effective soilborne disease control technology. In the management of soilborne diseases, the combined application of soil fumigation and seed rhizome treatment can reduce the risk of crops infected by soilborne diseases and ensure high and stable crop yields. © 2021 Society of Chemical Industry.

Estimated decline in global earthworm population size caused by pesticide residue in soil

Pesticides are potent chemical agents for protecting crops and agricultural production but can have secondary adverse effects on soil biodiversity that can propagate through all dimensions of soil security. Earthworms are among the most important actors in making soil healthy because they facilitate nutrient turnover, improve aeration, facilitate water infiltration into the root zone, and control soil-borne diseases. However, earthworms have been shown to be affected by the presence of pesticide residue, with a median survival to some highly toxic active substances concentrations as small as 4 mg/kg-soil. Here we have used the estimated pesticide residue of 87 active ingredients in nine different cropping systems globally, and we have developed the corresponding dose-response curve of earthworms to estimate the percent earthworm population decline and its global distribution caused by residues in the top soil. We found that vegetable and fruits, and orchards and grapes cropping systems are leading to the greatest percent decline in earthworms population in some areas of South America, and East and South East Asia. The decline in soybean, rice, and orchards and grape in boreal regions were the greatest. The maximum decline across the cropping systems ranged between 10 and 20% in about 1.2% of the agricultural locations under consideration, but it was less than 1% in about 66% of agricultural locations. These findings call for further scrutiny of the contamination by pesticide residue in soil and long-term consequences on soil security.

Impact of biocontrol microbes on soil microbial diversity in ginger (Zingiber officinale Roscoe).

Bacteria are the most diverse and abundant group of soil organisms that influence plant growth and health. Bacillus and Trichoderma are commonly used as biological control agents (BCA) that directly or indirectly act on soil bacteria. Therefore, it is essential to understand how the applied microbes impact the indigenous microbial community before exploring their activity in the control of soilborne diseases. MiSeq sequencing of the 16S rRNA gene was used to decipher the shift of rhizosphere bacterial community in ginger (Zingiber officinale Roscoe) treated with Bacillus subtilus and Trichoderma harzianum at different concentrations. The dominant phyla in treated and nontreated samples were Proteobacteria, Actinobacteria, Acidobacteria and comprised up to 54.7% of the total sequences. There were significant differences between BCA treated and nontreated samples in the bacteria community. BCA treated plants presented higher bacterial diversity than nontreated and higher dosage of BCA had a larger impact on rhizosphere microbiota, but the 'dose-response relationship' varied in different bacterial groups. Potential biomarkers at genus level were found, such as RB41, Pseudomonas, Nitrospira, Candidatus_Udaeobacter. The combined use of Bacillus subtilus and Trichoderma harzianum could alter bacterial community structure and diversity in rhizosphere soil. BCA-microbes interactions as well as soil microbial ecology should be noticed in plant disease management. © 2021 Society of Chemical Industry.

Wood pellets as carriers of conidia of Trichoderma atroviride SC1 for soil application

The use of biocontrol agents to control soilborne diseases is a promising alternative to chemical pesticides, however, obtaining a homogeneous distribution and incorporation of conidia of fungal biocontrol agents into the soil is often difficult. Several carriers/formulations have been proposed over time, unfortunately without offering an ultimate solution. We propose the use of wood pellets as a carrier of conidia of a saprophytic fungus that has good biodegradation and biocontrol properties (Trichoderma atroviride SC1). The coating process is based on the direct spraying of wood pellets with a conidial suspension at different rates. Beech, fir, and chestnut wood pellets were compared in terms of relevant physicochemical traits and efficacy in supporting the growth of the fungus. Beech wood pellets displayed the best characteristics in terms of water holding capacity, swelling properties, and disintegration time. T. atroviride SC1 grows best on beech and fir wood pellets and reaches a plateau after nine days of incubation, regardless of the initial coating concentrations. The addition of small quantities of a nitrogen source as tryptone or soy flour, soy proteins, and a mixture of animal proteins used as pet food to the conidial suspension can increase the growth by ten-folds on all types of wood pellets. Our results demonstrate that beech and fir wood pellets could be suitable carriers to deliver and sustain the growth of T. atroviride SC1.

Biodisinfestation With Agricultural By-Products Developed Long-Term Suppressive Soils Against Meloidogyne incognita in Lettuce Crop

Soil biodisinfestation is the process generated after the incorporation of organic amendments followed by a plastic cover to control soilborne diseases. Among organic amendments, the use of agricultural by-products could be an interesting alternative as it promotes circular economy. In this study, beer bagasse and defatted rapeseed cake together with fresh cow manure were incorporated into the soil (1.5, 0.5, and 20 kg/m2, fresh weight, respectively) to assess their capacity to reduce disease incidence caused by the root-knot nematode Meloidogyne incognita in protected lettuce crops and develop suppressive soils. The trial was conducted in a commercial greenhouse for 7 weeks during which temperature was continuously recorded at three different soil depths (15, 30, and 45 cm). Short- and long-term effects were assessed: before treatment, after treatment, after first crop post-treatment and one year post-treatment. Disease incidence and changes in nematode community structure were analyzed along with microbiological properties and general physicochemical parameters. After biodisinfestation, microbiological activity significantly increased in the treated soils and changes in the nematode community structure were detected in detriment of M. incognita and other plant-parasitic nematodes. These effects were more apparent after the first crop post-treatment than right after biodisinfestation. In the first crop after biodisinfestation, lettuce yield increased in the treated plots and root galling indices were significantly lower. One year after treatment, differences between treatments could be observed in the incidence of the damage caused by M. incognita that remained lower in the treated plots. In this trial, the addition of beer bagasse and rapeseed cake along with fresh manure in biodisinfestation treatment demonstrated nematicidal effects against M. incognita. Moreover, we suggest that the compounds released during the degradation of these by-products and the sub-lethal temperatures achieved in this trial during biodisinfestation (<42°C) were the key to develop suppressive soils in the long-term.

Bazı bitki türlerinin yeşil gübre olarak soğan sak nematodunun (Ditylenchus dipsaci) mücadelesi için in vitro etkinliği

Stem and bulb nematode, Ditylenchus dipsaci (Kühn, 1857) Filipjev, 1936, is a plant parasitic nematode that causes significant losses in plant production in the world. One of the promising methods for control of soil-borne diseases and pests that do not accumulate in nature is green manure application. Studies on the effectiveness of green manure on stem and bulb nematode are limited. In this study, the activity of 4 plant species from Brassicaceae family and one Tagetes patula L. variety on stem and bulb nematode was investigated in vitro. In the study, rates of motionless nematodes were recorded in the water and sand medium in 4 days and 11 days in five plant species. The efficiency of the plant species was increased over time. In all treatments in the study, the highest rate of motionless nematodes was obtained with arugula. On the 4th and 11th days in the water medium, 84.1% and 95.7% of motionless nematodes were obtained, respectively, while in the sand medium, the rate of motionless nematodes was 60.2% and 86.1%. Following the arugula, Tagetes patula showed activity at the rates of 72.9% and 98.3% in the water medium and 40.9% and 81.9% in the sand medium on the 4th and 11th days, respectively. Radish was also found promising with 62.5% and 94.2% in water medium, 59.2% and 80.9 in the sand medium, on the 4th and 11th days, respectively. The data obtained in the study provided preliminary data for green manure applications under field conditions.

Comparative Analysis of the Apple Root Transcriptome as Affected by Rootstock Genotype and Brassicaceae Seed Meal Soil Amendment: Implications for Plant Health.

Brassicaceae seed meal (SM) soil amendment has been utilized as an effective strategy to control the biological complex of organisms, which includes oomycetes, fungi, and parasitic nematodes, that incites the phenomenon termed apple replant disease. Soil-borne disease control attained in response to Brassicaceae SM amendment is reliant on multiple chemical and biological attributes, including specific SM-generated modifications to the soil/rhizosphere microbiome. In this study, we conducted a comparative analyses of apple root gene expression as influenced by rootstock genotype combined with a seed meal (SM) soil amendment. Apple replant disease (ARD) susceptible (M.26) and tolerant (G.210) rootstocks cultivated in SM-amended soil exhibited differential gene expression relative to corresponding non-treated control (NTC) orchard soil. The temporal dynamics of gene expression indicated that the SM-amended soil system altered the trajectory of the root transcriptome in a genotype-specific manner. In both genotypes, the expression of genes related to plant defense and hormone signaling were altered in SM-amended soil, suggesting SM-responsive phytohormone regulation. Altered gene expression was temporally associated with changes in rhizosphere microbiome density and composition in the SM-treated soil. Gene expression analysis across the two rootstocks cultivated in the pathogen-infested NTC soil showed genotype-specific responses indicative of different defensive strategies. These results are consistent with previously described resistance mechanisms of ARD “tolerant” rootstock cultivars and also add to our understanding of the multiple mechanisms by which SM soil amendment and the resulting rhizosphere microbiome affect apple rootstock physiology. Future studies which assess transcriptomic and metagenomic data in parallel will be important for illuminating important connections between specific rhizosphere microbiota, gene-regulation, and plant health.

Economic Analysis of Growing Grafted Cucumber Plants for High Tunnel Production

Cucumber (Cucumis sativus) is one of the most important vegetables produced and consumed in the United States. In the midwestern United States, a major obstacle to spring cucumber production is low soil temperatures during plant establishment. High tunnel is a popular tool for season extension of vegetable production. Low soil temperature is a challenge for cucumber production even inside high tunnels. Grafting is a cultural practice known to help control soilborne diseases and improve plants’ tolerance to abiotic stresses. Recent studies found that using grafted cucumber plants with cold-tolerant rootstocks greatly benefited early-season seedless cucumber production in high tunnels. The objective of this study was to analyze the economic feasibility of growing grafted cucumber in high tunnels. A comparison of partial costs and returns between growing grafted and nongrafted cucumbers in a high tunnel in Vincennes, IN, was conducted. Data were used to develop a partial budget analysis and sensitivity tests. Data included production costs, marketable yield, and price of cucumber through different market channels. This study provided a baseline reference for growers interested in grafting seedless cucumber and for high tunnel production. Although costs of grafted transplants were higher, their yield and potential revenue helped to offset the higher costs. Results indicated that grafting can help farmers increase net returns through the increasing yield of grafted plants. Results from the sensitivity analysis illustrated how the increased yield of grafted cucumbers offsets the extra cost incurred in the technique while providing a higher revenue. While actual production costs for individual farmers may vary, our findings suggested that grafting can be an economically feasible tool for high tunnel seedless cucumber production.