Root Rot Disease Severity Research Articles

The versatile plant probiotic bacterium Bacillus velezensis SF305 reduces red root rot disease severity in the rubber tree by degrading the mycelia of Ganoderma pseudoferreum1

Natural rubber is an indispensable material of strategic importance that has critical applications in industry and the military. However, the development of the natural rubber industry is impeded by the red root rot disease of rubber trees caused by Ganoderma pseudoferreum, which is one of the most devastating diseases in the rubber tree growing regions in China. To combat this disease, we screened the antifungal activity of 223 candidate bacterial strains against G. pseudoferreum, and found that Bacillus velezensis strain SF305 exhibited significant antifungal activity against G. pseudoferreum. B. velezensis SF305 had a nearly 70% efficacy against the red root rot disease of rubber trees with the therapeutic treatment (Tre), while it exhibited over 90% protection effectiveness with the preventive treatment (Pre). The underlying biocontrol mechanism revealed that B. velezensis SF305 could reduce the disease severity of red root rot by degrading the mycelia of G. pseudoferreum. An antiSMASH analysis revealed that B. velezensis SF305 contains 15 gene clusters related to secondary metabolite synthesis, 13 of which are conserved in species of B. velezensis, but surprisingly, B. velezensis SF305 possesses 2 unique secondary metabolite gene clusters. One is predicted to synthesize locillomycin, and the other is a novel nonribosomal peptides synthetase (NRPS) gene cluster. Genomic analysis showed that B. velezensis SF305 harbors genes involved in motility, chemotaxis, biofilm formation, stress resistance, volatile organic compounds (VOCs) and synthesis of the auxin indole-3-acetic acid (IAA), suggesting its plant growth-promoting rhizobacteria (PGPR) properties. B. velezensis SF305 can promote plant growth and efficiently antagonize some important phytopathogenic fungi and bacteria. This study indicates that B. velezensis SF305 is a versatile plant probiotic bacterium. To the best of our knowledge, this is the first time a B. velezensis strain has been reported as a promising biocontrol agent against the red root rot disease of rubber trees.

Evaluation of Enhancing Biochar and the fungus Glomus mosseae in the Growth of Common Bean, Phaseolus vulgaris infected with Rhizoctonia solani

Abed, R.M. 2024. Evaluation of Enhancing Biochar and the fungus Glomus mosseae in the Growth of Common Bean, Phaseolus vulgaris infected with Rhizoctonia solani. Arab Journal of Plant Protection, 42(2): 215-223. https://doi.org/10.22268/AJPP-001232 The possible role of biochar and its interaction with the fungus Glomus mosseae in promoting the growth of the common bean plant, Phaseolus vulgaris L., grown under biological stress of infection with the pathogenic fungus, Rhizoctonia solani was investigated. The results showed that the addition of biochar and the treatment with mycorrhizal fungus, and the interaction between them, led to a significant reduction in the seedling mortality and the severity of root rot disease of the common bean plant. The results obtained showed that the mycorrhizal traits, which included infection rate, severity of infection, and number of spores, were affected by the presence of the pathogenic fungus, as all the studied mycorrhizal traits decreased, compared to the treatment of the mycorrhizal fungus in the absence of the root rot fungus. The results obtained also showed that the decrease in the disease had a positive effect on the vegetative and root plant growth and nutrients content. The results obtained encourages the application of biochar as an alternative to chemical pesticides for the control of common bean root rot. Keywords: BioChar, common bean, Rhizoctonia solani, Glomus mosseae, mycorrhiza

Synergistic benefits of Funneliformis mosseae and Bacillus paramycoides: Enhancing soil health and soybean tolerance to root rot disease

To explore the response of soil metabolite composition to soybean disease, the effect of the combined inoculation of arbuscular mycorrhizal fungi (AMF) and plant growth-promoting bacteria on soybean root rot caused by Fusarium oxysporum was studied. A factorial completely randomized design with three factors (AMF, Bacillus. paramycoides, and rot disease stress) was conducted, and eight treatments, including normal groups and stress groups, were performed using pot experiments. GC‒MS and enzymatic assays were used to evaluate the soil factors and soybean growth indicators. The results showed that there were significant differences in the composition of metabolites among the different treatment groups, and 23 metabolites were significantly related to soybean biomass. The combined inoculation of Funneliformis mosseae and Bacillus paramycoides resulted in a significant reduction in harmful soil metabolites associated with root rot disease, such as ethylbenzene and styrene. This reduction in metabolites contributed to improving soil health, as evidenced by enhanced soybean defence enzyme activities and microbial activity, and β-1,3-glucanase, chitinase and phenylalanine ammonia-lyase activities were improved to alleviate plant rhizosphere stress. Furthermore, soybean plants inoculated with the synergistic treatments exhibited reduced root rot disease severity and improved growth indicators compared to control plants. Plant height, root dry weight (RDW), and shoot and root fresh weight (SRFW) were improved by 4.18–53.79%, and the AM fungal colonization rate was also improved under stress. The synergistic application of Funneliformis mosseae and Bacillus paramycoides can effectively enhance soil health by inhibiting the production of harmful soil metabolites and improving soybean tolerance to root rot disease. This approach holds promise for the sustainable management of soil-borne diseases in soybean cultivation.

Inoculum dose-disease response relationships for the pea root rot pathogen, Aphanomyces euteiches, are dependent on soil type and other pathogens.

The oomycete pathogen, Aphanomyces euteiches, was implicated for the first time in pea and lentil root rot in Saskatchewan and Alberta in 2012 and 2013. Subsequent surveys from 2014 to 2017 revealed that Aphanomyces root rot (ARR) was widespread across the Canadian prairies. The absence of effective chemical, biological, and cultural controls and lack of genetic resistance leave only one management option: avoidance. The objectives of this study were to relate oospore levels in autoclaved and non-autoclaved soils to ARR severity across soil types from the vast prairie landscape and to determine the relationship of measured DNA quantity of A. euteiches using droplet digital PCR or quantitative PCR to the initial oospore inoculum dose in soils. These objectives support a future end goal of creating a rapid assessment method capable of categorizing root rot risk in field soil samples to aid producers with pulse crop field selection decisions. The ARR severity to oospore dose relationship was statistically significantly affected by the soil type and location from which soils were collected and did not show a linear relationship. For most soil types, ARR did not develop at oospore levels below 100/g soil, but severity rose above this level, confirming a threshold level of 100 oospores/g soil for disease development. For most soil types, ARR severity was significantly higher in non-autoclaved compared to autoclaved treatments, demonstrating the role that other pathogens play in increasing disease severity. There was a significant linear relationship between DNA concentrations measured in soil and oospore inoculum concentration, although the strength of the relationship was better for some soil types, and in some soil types, DNA measurement results underestimated the number of oospores. This research is important for developing a root rot risk assessment system for the Canadian prairies based on soil inoculum quantification, following field validation of soil quantification and relationship to root rot disease severity.

Potential use of Terasi, an Indonesian traditional fermented seafood paste, to provide healthy lettuce (Lactuca sativa L.) seedling

Terasi paste consists of plant nutrients and microorganisms that potentially improve the health of plant seedlings. We evaluated the effects of terasi paste on seed germination, seedling growth, and root rot disease severity caused by Fusarium oxysporum f.sp. lactucae (FOL) in lettuce. Terasi paste was tested at four different weights (i.e., 0.00 g [T0], 1.00 g [T1], 2.50 g [T2], and 5.00 g [T3]) in the 100 g nursery soil. The results showed that lettuce seeds from T1 and T2 treatments were fully germinated, as observed for the T0 treatment. However, 40.0% of lettuce seeds from T3 treatment failed to germinate. Thus, 1.00 g and 2.50 g terasi applications in the 100 g soil did not affect lettuce seed germination. Moreover, T1 and T2 treatments tended to improve the shoot and root biomass of lettuce seedlings over T0 treatment, while T3 treatment showed the opposite effects. Following FOL infection, the lettuce seedlings from T2 and T3 treatments had 31.1% significantly lower disease severity than those from the T0 treatment. Therefore, T2 treatment (i.e., 2.50 g terasi application in the 100 g soil) imparts maximum health-promoting benefits to lettuce seedlings.

Efficacy and Timing of Application of Fungicides, Biofungicides, Host-Plant Defense Inducers, and Fertilizer to Control Phytophthora Root Rot of Flowering Dogwood in Simulated Flooding Conditions in Container Production.

Phytophthora root rot, caused by Phytophthora cinnamomi Rands, is one of the major diseases of flowering dogwood (Cornus florida L.). The severity of root rot disease increases when the plants are exposed to flooding conditions. A study was conducted to determine the efficacy and timing of application of different fungicides, biofungicides, host-plant defense inducers, and fertilizer to manage Phytophthora root rot in month-old seedlings in simulated flooding events for 1, 3, and 7 days. Preventative treatments were drench applied 3 weeks and 1 week before flooding whereas curative treatments were applied 24 h after flooding. Dogwood seedlings were inoculated with P. cinnamomi 3 days before the flooding. Plant height and width were recorded at the beginning and end of the study. At the end of the study, plant total weight and root weight were recorded and disease severity in the root was assessed using a scale of 0 to 100%. Root samples were plated using PARPH-V8 medium to determine the percent recovery of the pathogen. Empress Intrinsic, Pageant Intrinsic, Segovis, and Subdue MAXX, as preventative and curative applications, were able to suppress the disease severity compared with the inoculated control in all flooding durations. All treatments, with the exception of Stargus as a preventative application 3 weeks before flooding and Orkestra Intrinsic as a curative application, were able to suppress the disease severity compared with the inoculated control for a 1-day flooding event. Aliette and ON-Gard were effective in the first trial when applied preventatively at both 1 week and 3 weeks before flooding but not in the second trial. Signature Xtra was effective as a preventative application but not as a curative application. Interface was effective as a curative application but not as a preventative application. The findings of this study will help nursery growers to understand the performance of fungicides, biofungicides, host-plant defense inducers, and fertilizer at different time intervals and repeated applications to manage Phytophthora root rot in flooding conditions.

Control of Phytophthora and Rhizoctonia Root Rot on Red Maple Using Fungicides and Biofungicides

Phytophthora nicotianae and Rhizoctonia solani are the well-described soilborne pathogens of concern causing Phytophthora and Rhizoctonia root rot, respectively, of red maple plants (Acer rubrum L.), resulting in substantial economic losses to nursery growers. The management of root and crown rot disease of red maple is a big challenge. The objective of this study was to test the efficacy of several fungicide and biofungicide products to control Phytophthora and Rhizoctonia root rot on red maple plants in greenhouse conditions. Treatments, including fungicides and biofungicides, and nontreated and inoculated and nontreated and noninoculated as controls were arranged in a completely randomized design with six replications. Red maples planted in number 1 nursery containers were artificially inoculated with P. nicotianae or R. solani. Plant height, plant width, total fresh weight, and root fresh weight were measured and roots were assessed for root rot disease severity based on a scale of 0% to 100% root damaged. The pathogen recovery percentage of plant roots was determined by culturing ten randomly selected root pieces (≈1 cm long) cut from the root tips on Phytophthora selective medium (PARPH-V8) or Rhizoctonia semi-selective medium. All tested fungicides and biofungicides reduced Phytophthora and Rhizoctonia root rot on red maple plants compared with the nontreated and inoculated control. Likewise, pathogen recovery was lower for fungicide-treated and biofungicide-treated plants. Fungicides, such as mefenoxam, oxathiapiprolin, pyraclostrobin plus boscalid, and pyraclostrobin provided the most effective control of Phytophthora root rot. Pyraclostrobin plus boscalid and pyraclostrobin followed by biofungicides Bacillus amyloliquefaciens strain F727 and Trichoderma harzianum Rifai strain T-22 plus T. virens strain G-41 were most effective for suppressing Rhizoctonia root rot. There were no differences in plant height, plant width, plant fresh weight, and root fresh weight among the treatments. These findings will help nursery producers make decisions while formulating soilborne disease management strategies for red maple production.

Comparative Performance of Fungicides, Biofungicides, Host-plant Defense Inducers, and Fertilizer in Management of Phytophthora Root Rot on Boxwood

Phytophthora root rot, caused by Phytophthora nicotianae Breda de Haan, is one of the destructive diseases of boxwood (Buxus sempervirens L.) and can affect all growth stages of field- and container-grown boxwood plants. Management is a problem and is only possible through an integrated approach. In this study, the efficacy of fungicides, biofungicides, host-plant defense inducers, and fertilizer were evaluated to manage Phytophthora root rot of boxwood. The objective of this experiment was to develop fungicide and biofungicide recommendations for Phytophthora root rot management in boxwood production. Field and greenhouse experiments were conducted in 2019 (Trial 1) and 2020 (Trial 2). The field experiment was arranged in a completely randomized design with four plots per treatment with five single ‘Green Velvet’ boxwood plants per plot. The greenhouse experiment was arranged in a completely randomized design with five single ‘Green Velvet’ container-grown boxwood plants per treatment. Plots/containers were inoculated with P. nicotianae grown on rice grains. Plant growth data such as height and average width were recorded at the beginning and end of the experiments. Total plant fresh weight and root fresh weight were recorded at the end of the experiments. Roots were assessed for root rot disease severity using a scale of 0% to 100% roots affected. Treatments used in both experiments were fungicides—ametoctradin + dimethomorph, fluzapyroxad, mefenoxam, oxathiapiprolin, pyraclostrobin, pyraclostrobin + boscalid; host-plant defense inducers—aluminum tris-drench, aluminum tris-foliar, potassium salts of phosphoric acid; biofungicides—Trichoderma harzianum Rifai strain T-22 + Trichoderma virens strain G-41, Bacillus amyloliquefaciens Priest; fertilizer—water-soluble nitrogen (nitrogen 5%) and soluble potash; and combination of water-soluble nitrogen, soluble potash, and T. harzianum Rifai strain T-22 + T. virens strain G-41. All treatments were drench applied except one of the aluminum tris, which was applied as foliar. The controls were nontreated, inoculated and nontreated, and noninoculated boxwood plants. In the greenhouse experiments, treatments that effectively reduced disease severity were pyraclostrobin, ametoctradin + dimethomorph, and oxathiapiprolin. In the field experiments, treatments such as pyraclostrobin, oxathiapiprolin, mefenoxam, fluzapyroxad, and combination of water-soluble nitrogen (nitrogen 5%), soluble potash, and T. harzianum Rifai strain T-22 + T. virens strain G-41 effectively reduced Phytophthora root rot severity. Oxathiapiprolin and pyraclostrobin are the chemical fungicides that were effective in both field and greenhouse experiments.

BIOLOGICAL CONTROL OF THE COMPLEX DISEASE OF Rhizoctonia solani AND ROOT-KNOT NEMATODE Meloidogyne javanica ON CHICKPEA BY Glomus spp. AND Pseudomonas sp.

Rhizoctonia-Meloidogyne complex disease is a serious problem facing legume production in many countries. The infection of chickpea (Cicer arietinum) by pathogens Rhizoctonia solani (R) and Meloidogyne javanica (M) in a single infection or combination causes severe damage to plant growth. The effect of using Glomus spp. (G) and Pseudomonas sp. (P) as a biological control agent against Rhizoctonia- Meloidogyne complex disease was tested and assessed by comparing the growth and disease parameters in infected and control plants. Chickpea growth parameters are characterized by measuring shoot and root length, and fresh and dry weight. The results of using (G) and (P) in a single treatment or in combination showed a decrease in the root gall index and in root rot disease severity when compared to the infected and healthy control treatments. The (M+ R+ G) and (M + R + G + P) combination treatment increased polyphenol oxidase (POD) and peroxidase (PPO) enzyme activity value as well as the total phenols content in treated chickpea roots. The combined effects of (G) and (P) on the pathogens’ progression and the positive effects on chickpea growth parameters are suggested to be involved in efficient disease control.

Resistance Induction by Salicylic Acid Formulation in Cassava Plant against Fusarium solani.

Fusarium root rot caused by the soil-borne fungus Fusarium solani is one of the most important fungal diseases of cassava in Thailand, resulting in high yield losses of more than 80%. This study aimed to investigate if the exogenous application of salicylic acid formulations (Zacha) can induce resistance in cassava against Fusarium root rot and observe the biochemical changes in induced cassava leaf tissues through synchrotron radiation based on Fourier-transform infrared (SR-FTIR) microspectroscopy. We demonstrated that the application of Zacha11 prototype formulations could induce resistance against Fusarium root rot in cassava. The in vitro experimental results showed that Zacha11 prototype formulations inhibited the growth of F. solani at approximately 34.83%. Furthermore, a significant reduction in the disease severity of Fusarium root rot disease at 60 days after challenge inoculation was observed in cassava plants treated with Zacha11 at a concentration of 500 ppm (9.0%). Population densities of F. solani were determined at 7 days after inoculation. Treatment of the Zacha11 at a concentration of 500 ppm resulted in reduced populations compared with the distilled water control and differences among treatment means at each assay date. Moreover, the SR-FTIR spectral changes of Zacha11-treated epidermal tissues of leaves had higher integral areas of lipids, lignins, and pectins (1,770–1,700/cm), amide I (1,700–1,600/cm), amide II (1,600–1,500/cm), hemicellulose, lignin (1,300–1,200/cm), and cellulose (1,155/cm). Therefore, alteration in defensive carbohydrates, lipids, and proteins contributed to generate barriers against Fusarium invasion in cassava roots, leading to lower the root rot disease severity.

Increased Resilience of Peas Toward Root Rot Pathogens Can Be Predicted by the Nematode Metabolic Footprint

Legumes are important drivers of soil fertility, however, their frequent use in rotations fosters long-lived soil-borne pathogens that can seriously compromise legume root health and nitrogen fixation. To overcome this, the current study aims at improving the general soil suppressiveness toward pests and diseases by agroecosystem management that can be predicted by nematode-based bioindicators. Two long-term organically managed agroecosystems comparing plow and shallow non-inversion tillage were analyzed for free-living nematode communities. Soils out of these agroecosystems were evaluated further in a greenhouse assay for their ability to suppress pea root rot caused by Didymella pinodella, Fusarium avenaceum, and F. redolens. There was a general trend for higher levels of pea root rot disease severity following inoculations with single pathogens, however, this effect was heterogeneous among experiments and tillage systems. This was mainly due to an already very high resident population of D. pinodella in soil and the presence of seed-borne F. oxysporum determined by their high incidence in pea roots irrespective of the soil and inoculated pathogens. Additional inoculation with D. pinodella, for example, resulted in only 8.5% biomass reduction compared to the non-inoculated control, in both tillage systems. Similar biomass losses were recorded in non-inversion tilled soils inoculated with F. redolens. When analyzed across inoculation treatments, the pea root rot disease severity was only slightly reduced in non-inversion tilled soils when compared to the plough systems (11% in Exp 1 and, 9% in Exp 2), however in both experiments non-inversion tillage resulted in greater pea biomass (33 and 19% in Exp1 and 2, respectively). Furthermore, the metabolic, enrichment, and bacterivore carbon footprints of nematodes were 88, 81, and 97% higher, respectively, in the non-inversion tilled soils compared to the plough. The metabolic carbon footprint of nematodes correlated negatively with pea root rot disease severity (rho = −0.71, p = 0.047). Hence, non-inversion tillage was effective in controlling pea root rot. The use of nematode metabolic footprints for predicting soil health should be extended for various agroecosystems aiming for its general use in evaluating effects of agroecosystem management through researchers and potentially farm management advisors.

Smart pH responsive system based on hybrid mesoporous silica nanoparticles for delivery of fungicide to control Fusarium crown and root rot in tomato

Mesoporous silica nanoparticles (MSNs) can promote the solubility and absorption of pesticides by plants and are widely used as a delivery system to improve the efficacy of pesticide applications. In this study, MSNs with 20 nm particle size were produced. Additionally, a water-soluble chitosan (CS) derivative, here called N-(2-Hydroxyl) propyl-3- tri-methyl-ammonium CS chloride (HTCC) was produced and used to cap the outer surface of the MSNs preloaded with the pesticide fludioxonil (Flu). The HTCC coating layers resulted in a pesticide loading efficiency of 84% on the MSNs in comparison to a loading efficiency of 20% of uncoated particles. A comparative in vitro analysis indicated that Flu@MSNs20nm-HTCC loaded with a 0.05 mg/L dose of fungicide had significant higher fungicidal activity than the same fungicide at 1 mg/L dose against F. oxysporum f. sp. radicis-lycopersici (FORL). Moreover, after an initial burst, MSNs20nm-HTCC kept releasing Flu for 21 d, compared to an activity of 7 d associated with the direct release of Flu. Greenhouse data showed that 0.1 mg/L Flu applied through MSNs20nm-HTCC is sufficient to reduce Fusarium crown and root rot disease severity to a value of less than 6% in tomato plants, without any noticeable phytotoxicity after 70 d. In comparison, 1.56 mL/L of the fungicide are required to reach a 27% disease severity level. Thus, we suggest that HTCC-decorated MSNs20nm has a great potential as a nanodelivery systems for agrochemical applications. We also suggest that this work contributes to the notion that agro-nanotechnology is a powerful, environmentally-safe and cost-effective approach for a sustainable and long term protection of plants from disease.

Production strategies management to minimize root rot disease in field pea grown on infected southwestern Saskatchewan soils

Multilocational field studies were conducted near North Battleford, Wilkie and Cando in Saskatchewan (SK), Canada during the 2015 (year 1) and 2016 (year 2) summer crop growing seasons to evaluate Aphanomyces euteiches Drechs and Fusarium root rot response to different seed place fertility, preemergence herbicide combination, and foliar fertility. Seven seed place fertility treatments (F1 to F7) were Nitrogen and phosphorus inoculant, liquid Optimize inoculant (LCO), LCO /5.5-25-0-0 (N-P-K-S), LCO /15-25-0-0, LCO /15-25-0-15, LCO/liquid orthophosphate (2-8-1) at 33.7 L/ha/15-0-0-15 and LCO/15-40-40-15 respectively. The four preemergence herbicide (P RE1 to P RE4) were: Glyphosate/Saflufenacil; Glyphosate/Sulfentrazone/Carfentrazone; Glyphosate/Sulfentrazone/Pyroxasulfone and Glyphosate/Sulfentrazone/Trifluralin. Pea was treated with five postemergence (POST 1-5) herbicide with/without adjuvants/foliar fertility at 4-5 node stage as Imazamox/bentazon (Viper) plus 28% v/v Urea Ammonium Nitrate (UAN) – POST 1; Viper plus 2X 28% UAN – POST 2; Viper plus 1X 28% UAN plus foliar fertility – POST 3; Viper plus 2X 28% UAN plus foliar fertility – POST 4 and Quizalofop-p-ethyl at 494.23 mL/ha – POST 5. Growth response, root rot disease severity and yield (kg/ha) were analyzed using SAS statistical software. Significant means were at F < 0.05 were separated by the Fisher’s Protected LSD test at the 5% level. Root rot was significantly lower in P RE4 compared to other treatments. Postemergence herbicide treatments and seed-place fertility recorded significant interaction on root rot incidence and yield. There was over 30% yield improvement between 2016 and 2015 trials due to soil moisture. The trial minimized pea root rot from infested soils and increased yield.

Phytopythium vexans Associated with Apple and Pear Decline in the Saïss Plain of Morocco.

An extensive survey conducted in the Saïss plain of Morocco during the 2017–2018 growing season revealed that 35 out of 50 apple and pear orchards were infested with a pathogen that causes the decline disease. Morphological and phylogenetic tree analyses using the cox II gene allowed us to identify the pathogen as Phytopythium vexans. Interestingly, no Phytophthora and Pythium species were isolated. The occurrence and prevalence of the disease varied between locations; the most infested locations were Meknes (100%), Imouzzer (83%), and Sefrou (80%). To fulfill Koch’s postulate, a greenhouse pathogenicity test was performed on the stem and collar of one-year-old healthy seedlings of apple rootstock M115. Symptoms similar to those observed in the field were reproduced in less than 4 months post-inoculation with root rot disease severity ranging from 70 to 100%. The survey results evidenced that apple rootstocks, soil type, and irrigation procedure may contribute significantly to the occurrence of the disease. The disease was most prevalent in drip water irrigation and sandy-clay soil on wild apple rootstock. Accordingly, a rational drip advanced watering system and good sanitation practices could eliminate water stagnation and help prevent the onset of this disease. It was concluded that Pp. vexans occurrence may be strongly influenced by irrigation mode and type of soil. Therefore, the obtained findings of this study could help to better understand the recurrence of this disease and to develop a reliable integrated strategy for its management.

Exploitation of Agro-Industrial Residues for the Formulation of a New Active and Cost Effective Biofungicide to Control the Root Rot of Vegetable Crops

This study aimed to produce an economic and stable biofungicide based on a new effective antagonistic strain (Trichoderma harzianum JF419706) via the exploitation of agro-industrial lignocellulosic residues as carriers for fungal growth to control the root rot diseases of vegetable crops. Trichoderma harzianum JF419706 showed a good resistance to a chemical fungicide with two-fold of the recommended dose. It was able to propagate on corn stovers amended with 20% of date molasses, as a very cheap substrate, up to 2.90 × 1016 CFU/g after 30 days. Formulation of the bioagent on the substrate as a fine powder (FTB) increased the shelf-life up to 8 months with good viability (9.37 × 1011 CFU/g). The bioagent propagated itself in the rhizospheric soil about two-fold of the initial inoculum. Application of the FTB, as a seed treatment, suppressed the root rot disease severity percentage of cucumber, lettuce, and tomato plants to 70.0%, 61.5%, and 53.8%, respectively, from the control. The crop yield increased by 50%, 35%, and 30% in the same order of the three crops. FTB promoted the growth and physiological processes of the plants significantly compared with the control. Our study recommends the application of the FTB as a cost-effective biofungicide and biofertilizer in crop management, singly or as a part of integrated pest management, to ensure the sustainability of green farming and reduce the chemical input in cultural practices.

Response of Cover Crops to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani, Major Soilborne Pathogens of Woody Ornamentals

Management of plant diseases is a subject of concern for researchers as well as growers. Different management practices are being developed and used to combat the rising number of plant pathogens, which threaten nursery crop production. Use of cover crops for sustainable management of soilborne diseases is being explored as an alternative strategy to the chemicals. However, the potential threat of these cover crops acting as a secondary host of these devastating soilborne pathogens has not been described. We studied the response of the major cover crops being used by woody ornamental growers in the Southeastern United States to Phytopythium vexans, Phytophthora nicotianae, and Rhizoctonia solani in greenhouse conditions to identify the effective cover crops that can be used in a nursery field production system. Data related to post-emergence damping-off and plant growth parameters (plant height increase and fresh weight) were recorded. Similarly, cover crop roots were assessed for root rot disease severity using a scale of 0–100% roots affected. Among the tested cover crops, the grass cover crops triticale (×Triticosecale Wittm. ex A. Camus.), annual ryegrass (Lolium multiflorum L.), Japanese millet (Echinochloa esculenta (A. Braun) H. Scholz), and the legumes Austrian winter pea (Pisum sativum var. arvense (L.) Poir) and cowpea ‘Iron and Clay’ (Vigna unguiculata (L.) Walp.), showed lower root rot disease severity and post-emergence damping-off in the soil inoculated with P. nicotianae, R. solani, or P. vexans compared to the other crops. Since these cover crops can act as non-host crops and benefit the main crop in one way or another, they can be used in the production system. Further research is recommended to evaluate their performance in a natural field setting.

Impact of chitosan seed treatment of fenugreek for management of root rot disease caused by Fusarium solani under in vitro and in vivo conditions.

The use of chitosan as an alternative for fungicides has received more attention worldwide. Hence, this study aimed to evaluate in vitro and in vivo antifungal activity of chitosan against Fusarium solani causing root rot in fenugreek. Chitosan treatments ranged from 0.1 to 2gL-1 were tested against F. solani on to potato dextrose agar and in potato dextrose broth. The results revealed that increase in concentrations of chitosan significantly reduced growth, dried biomass, sporulation and spore germination of F. solani. The hyphal swellings and distortion of F. solani mycelia were induced by chitosan. Fenugreek seeds treated with chitosan at 2 gL-1 and 0.5 gL-1 showed reduced F. solani infection and increased seed germination, respectively. In pot and field studies, fenugreek seeds treated with chitosan at 2.0 gL-1 greatly reduced root rot disease severity and also enhanced yield parameters. The activity of defence enzymes, such as chitinase, β-1, 3-glucanase and total phenol were increased in chitosan treated in fenugreek plants. This increased activity offered protection to fenugreek plants against F. solani to a greater extent. The results showed that chitosan could be used as inducer of defense response and has the potential of controlling fenugreek root rot disease.

Bacillus megaterium-Mediated Synthesis of Selenium Nanoparticles and Their Antifungal Activity against Rhizoctonia solani in Faba Bean Plants.

Rhizoctonia root-rot disease causes severe economic losses in a wide range of crops, including Vicia faba worldwide. Currently, biosynthesized nanoparticles have become super-growth promoters as well as antifungal agents. In this study, biosynthesized selenium nanoparticles (Se-NPs) have been examined as growth promoters as well as antifungal agents against Rhizoctonia solani RCMB 031001 in vitro and in vivo. Se-NPs were synthesized biologically by Bacillus megaterium ATCC 55000 and characterized by using UV-Vis spectroscopy, XRD, dynamic light scattering (DLS), and transmission electron microscopy (TEM) imaging. TEM and DLS images showed that Se-NPs are mono-dispersed spheres with a mean diameter of 41.2 nm. Se-NPs improved healthy Vicia faba cv. Giza 716 seed germination, morphological, metabolic indicators, and yield. Furthermore, Se-NPs exhibited influential antifungal activity against R. solani in vitro as well as in vivo. Results revealed that minimum inhibition and minimum fungicidal concentrations of Se-NPs were 0.0625 and 1 mM, respectively. Moreover, Se-NPs were able to decrease the pre-and post-emergence of R. solani damping-off and minimize the severity of root rot disease. The most effective treatment method is found when soaking and spraying were used with each other followed by spraying and then soaking individually. Likewise, Se-NPs improve morphological and metabolic indicators and yield significantly compared with infected control. In conclusion, biosynthesized Se-NPs by B. megaterium ATCC 55000 are a promising and effective agent against R. solani damping-off and root rot diseases in Vicia faba as well as plant growth inducer.

Efficiency of bio-evaporation of Arugula leaves to control root rot disease on cucumber caused by Pythium intermedium in Greenhouse

The efficiency of the Arugula (Eruca vesicaria) leaves extracts against the fungus Pythium intermedium, the root rot disease agent, was evaluated with three concentrations of 2.5, 5, 10 g / kg soil as biofumigation. The fungi around infected root of cucumber plants were isolated and diagnosed from different locations in Baghdad such as Rashidiya, Madaen, Yousifiya and Mahmudiya. The extract of arugula plants significantly reduced the incidence and severity of root rot disease on cucumber plant after 45 days of cultivation compared with control. The highest reduction in incidence and severity of the disease was about 4% and 5% respectively with arugula extract 10 g / kg soil. The study was the first record to evaluate the incidence of P. intermedium on root of cucumber plants in Iraq. Further, all concentrations of arugula extract showed increase on the growth parameters compared with control. In arugula extract 10 g/kg soil the growth parameter such as plant length, leaf length, leaf width, wet weight and dry weight were 35 cm, 5.5 cm, 6 cm, 4 g and 0.28 g respectively. Furthermore, Significant differences in the value of the biological index of arugula plant extract treatments ranging from 2627 to 3433 compared to the treatment of P. intermedium, which was about 1910, while did not differ significantly from the treatment of control with a vital index of 3830.

Impact of Cover Crop Usage on Soilborne Diseases in Field Nursery Production

Soilborne pathogens are a significant economic problem for nursery production in the Southeastern United States. The goal of this study was to determine the impact of cover crops on soilborne disease suppressiveness in such systems. Soils from red maple (Acer rubrum L.) plantation fields grown with and without cover crops were sampled, either while the cover crops were growing (pre-disked) or post-season, following cover crop incorporation into the soil (post-disked). Greenhouse bioassays were conducted using red maple seeds on inoculated (with Rhizoctonia solani (J.G. Kühn) or Phytophthora nicotianae (Breda de Haan)) and non-inoculated field soils. The damping-off, root rot disease severity, percent recovery of Rhizoctonia and Phytophthora, and pseudomonad population were examined during the two years of the experiment. Results showed that cover crop incorporation was beneficial for inducing disease supressiveness characteristics of soil. Cover crop incorporation into the soil significantly or numerically reduced disease severity and pathogen recovery in infested soil compared to the bare soil treatment. Cover crop incorporation was found to be partially associated with the reduction of seedling damping-off. The pseudomonad microbial population was greater when cover crop was present, and is thought to be antagonist to soilborne pathogens. Therefore, cover crops can be integrated in field nursery production systems to suppress soilborne pathogens.