Use of Lentinan and Fluopimomide to Control Cotton Seedling Damping-Off Disease Caused by Rhizoctonia solani

Lentinan (LNT) is a natural and functional polysaccharide isolated from Lentinus edodes fruiting bodies, which functions in stimulating the plant immune response, improving plant disease resistance and regulating plant growth. This study explores the use of LNT as a plant growth regulator and attractant in cotton production. After treatment with LNT, the content of malondialdehyde (MDA) in cotton seeds decreased, whereas the activities of polyphenol oxidase (PPO), superoxide dismutase (SOD) and peroxidase (POD) in leaves increased significantly. LNT also promoted the growth and development of cotton plants and significantly reduced the incidence of cotton damping-off disease. The relative expression of salicylic acid pathway-related genes in cotton also increased significantly. The prevention mechanism of fluopimomide was also evaluated, and the result showed lower EC50 values and was effective in controlling cotton seedling disease caused by Rhizoctonia solani in both greenhouse experiments and field trials. The use of LNT and fluopimomide in controlling cotton seedling damping-off disease showed a synergistic effect in field trials. These results will provide a new insight into the agricultural application of LNT as a biological fungicide in the field of biological controls.

An integrated pest management program outperforms conventional practices for tomato (Solanum lycopersicum L.) in Cambodia

For several years, pest management in tomato production in Cambodia has generally focused on the use of synthetic pesticides. We compared conventional pest management (farmers’ traditional practices) with an IPM program on 12 farms in the northwestern part of Cambodia. The IPM program combined cultural, biological, and chemical practices. We found that IPM practices reduced aphid damage by 46% and diseases such as Fusarium wilt and damping-off were substantially reduced. Our results indicate that the IPM package increased tomato yield and income by an average of 23% and 34%, respectively, compared to conventional practices during both dry and rainy seasons.

Characterization and pathogenicity of a Pythium aphanidermatum isolate causing ‘damping off’ in pepper seedlings

<p>The production of the pepper seedling (<em>Capsicum annuum</em>) is affected by the fungal complex that causes the ‘damping-off’, in which some species of the oomycete <em>Pythium</em> spp., stand out. The objective of the present study was to identify the causal agent of the death of pepper plants and evaluate its pathogenicity in pepper seeds and seedlings. A fast and aggressive growing oomycete was isolate from pepper plants, morphologically identified as P. aphanidermatum based on its sexual and asexual reproduction structures and, by molecular techniques. This isolate had a high degree of<em> in vitro</em> pathogenicity in pre-emergence and post-emergence in chile, showing 100% mortality. In addition, it presented a high rate of mycelial growth in different culture media (V8-Agar, Corn Agar, Corn Potato Agar, Potato Dextrose Agar, Czapek &amp; Oat Agar), being in V8-Agar medium the only medium where it developed reproduction structures sexual and asexual. The isolation presented a mycelial growth rate of 58.3 ± 0.3 mm / day at 26 ± 2 °C in PDA medium. Due to its rapid growth and its high degree of pathogenicity <em>in vitro</em>, it is an unusual and aggressive isolate for pepper seedlings.</p>

Silicon Dioxide Nanoparticles Induce Innate Immune Responses and Activate Antioxidant Machinery in Wheat Against Rhizoctonia solani

The phytopathogenic basidiomycetous fungus, Rhizoctonia solani, has a wide range of host plants including members of the family Poaceae, causing damping-off and root rot diseases. In this study, we biosynthesized spherical-shaped silicon dioxide nanoparticles (SiO2 NPs; sized between 9.92 and 19.8 nm) using saffron extract and introduced them as a potential alternative therapeutic solution to protect wheat seedlings against R. solani. SiO2 NPs showed strong dose-dependent fungistatic activity on R. solani, and significantly reduced mycelial radial growth (up to 100% growth reduction), mycelium fresh and dry weight, and pre-, post-emergence damping-off, and root rot severities. Moreover, the impact of SiO2 NPs on the growth of wheat seedlings and their potential mechanism (s) for disease suppression was deciphered. SiO2 NPs application also improved the germination, vegetative growth, and vigor indexes of infected wheat seedlings which indicates no phytotoxicity on treated wheat seedlings. Moreover, SiO2 NPs enhanced the content of the photosynthetic pigments (chlorophylls and carotenoids), induced the accumulation of defense-related compounds (particularly salicylic acid), and alleviated the oxidative stress via stimulation of both enzymatic (POD, SOD, APX, CAT, and PPO) and non-enzymatic (phenolics and flavonoids) antioxidant defense machinery. Collectively, our findings demonstrated the potential therapeutic role of SiO2 NPs against R. solani infection via the simultaneous activation of a multilayered defense system to suppress the pathogen, neutralize the destructive effect of ROS, lipid peroxidation, and methylglyoxal, and maintain their homeostasis within R. solani-infected plants.

Evaluation of damping-off tolerance in spinach cultivars in field soils and in a standardized lab assay with Pythium ultimum

Spinach growers face increasing problems of damping off in the production of fresh market (baby-leaf) spinach due to increasing restrictions on chemical treatments. Damping-off tolerant cultivars are increasingly important, requiring proper evaluation methods. From three locations in the Netherlands with a history of spinach cultivation and from one location in France, potential damping-off pathogens were isolated from the soil, identified to species or genus, and tested for their pathogenicity. Pythium ultimum was the most prevalent pathogen in those fields, causing spinach pre- and post-emergence damping off. Eight spinach cultivars with two or three seed lots each, were evaluated at the same field locations and in a greenhouse with soil sampled from one of the Dutch field sites. Pre-emergence damping off was more discriminating for differences among the cultivars than post-emergence damping off. Variation in levels of infection among trials, replicates, and seed lots of same cultivars, emphasized the need for a more standardized phenotyping assay. For such an assay, a cornmeal/sand-based inoculum with a pathogenic P. ultimum isolate was added to a substrate mixture of sand, perlite, and vermiculite, moistened until 50% water holding capacity, in which spinach seeds were incubated for ten days in a dark climate cabinet at 15°C, including a control treatment without P. ultimum inoculum. The assay showed reproducible results for discriminating differences in pre-emergence damping-off tolerance levels among seed lots. However, cultivar differences in pre-emergence damping-off tolerance levels could not be confirmed due to a large variation among seed lots that needs further investigation.

Beneficial effect of Achromobacter insolitus MB20 and manures in reducing Pythium aphanidermatum disease in cucumber

The increased global livestock production, such as chickens, cows, goats, and rabbits causes increased animal waste in both liquid and solid forms. The utilization of animal manures are considered as a beneficial way to minimize the livestock waste problems. Application of manure is advantageous to the soil nutrient balance, soil structure and moisture-holding capacity, and facilitates environmental protection. A combination of biocontrol agent of Achromobacter insolitus MB20 and manures was studied as alternative to chemical fungicides to protect crop from diseases without damaging the environment and human health. The chemical fungicides cannot be used continously and do not represent a sustainable method control. Result showed that an application of A. insolitus alone reduced cucumber damping-off as high as 60%, and in combination of A. insolitus with chicken manure was 80%, goat manure 70%, cow manure and rabbit urine 65%. The in vitro test indicated that A. insolitus inhibited P. aphanidermatum growth by 28%. This antagonist bacterium also produced extracellular enzyme of protease and cellulase with proteolytic index (PI) value was 1.4 and cellulolytic index (CI) value was 1.7. An application of A. insolitus with chicken manure resulted the best combination and the most effective in reducing of cucumber damping-off.

Evaluation Efficiency of Different Isolate of Actinomycetes for Control of Cucumber Seedling Damping-off Disease Caused by Rhizoctonia solani (Khun)

Fayyadh, M.A. and L.K. Awad. 2021. Evaluation Efficiency of Different Isolate of Actinomycetes for Control of Cucumber Seedling Damping-off Disease Caused by Rhizoctonia solani (Khun). Arab Journal of Plant Protection, 39(4): 281-288. https://doi.org/10.22268/AJPP-39.4.281288 This study was conducted in Plant Protection Department, College of Agriculture, University of Basrah during the period 2017-2018 aimed to isolate and identify Actinomycetes from different environmental sources and evaluate their efficiency to control cucumber damping off disease caused by Rhizoctonia solani. 28 isolates of Actinomycetes were isolated from different sources from the Basrah region. All such isolates were gram positive, amylase and catalase positive and they had branched hyphae. Molecular identification following amplification of 16sRNA confirmed that Actinomycetes isolate No 6 isolated from soil had a similarity of 99% with Streptomyces griseus, whereas the isolate No 66 isolated from date palm roots had a similarity of 99% with Brevibacterium celere. The nucleotide sequence of the two isolates has been deposited at NCBI with Genbank accession number LC501385.1 for S. griseus and LC501386.1 for B. celere. The dual culture technique showed that Actinomycetes isolates S. griseus and B. celere had high antagonistic activity against Rhizoctonia solani, which produced inhibition zones of 7 and 15 mm in dimeter, respectively. On the other hand, volatile compoundsreleased from S. griseus and B. celere inhibited the growth of R. solani by 68 and 81.5%, respectively. Pot experiment showed that all actinomycetes isolates significantly reduced cucumber seedling damping–off incidence caused by R. solani. Keywords: Actinomycetes, Rhizoctonia solani, Cucumber, Biological Control