Publications by authors named "Mahmoud H El Komy"

7 Publications

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Molecular and physiological characterization of Fusarium strains associated with different diseases in date palm.

PLoS One 2021 22;16(7):e0254170. Epub 2021 Jul 22.

Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.

Several species of Fusarium cause serious diseases in date palm worldwide. In the present work, 14 SSR markers were used to assess the genetic variation of Fusarium strains isolated from diseased trees in Saudi Arabia. We also studied the effect of different temperatures on mycelial growth of these strains. The pathogenicity of four strains of F. proliferatum was also evaluated on local date palm cultivars. Eleven SSR markers amplified a total of 57 scorable alleles from Fusarium strains. Phylogenetic analysis showed that F. proliferatum strains grouped in one clade with 95% bootstrap value. Within F. proliferatum clade, 14 SSR genotypes were identified, 9 of them were singleton. Four out of the five multi-individual SSR genotypes contained strains isolated from more than one location. Most F. solani strains grouped in one clade with 95% bootstrap value. Overall, the SSR markers previously developed for F. verticillioides and F. oxysporum were very useful in assessing the genetic diversity and confirming the identity of Saudi Fusarium strains. The results from the temperature study showed significant differences in mycelial growth of Fusarium strains at different temperatures tested. The highest average radial growth for Fusarium strains was observed at 25°C, irrespective of species. The four F. proliferatum strains showed significant differences in their pathogenicity on date palm cultivars. It is anticipated that the assessment of genetic diversity, effect of temperature on hyphal growth and pathogenicity of potent pathogenic Fusarium strains recovered from date palm-growing locations in Saudi Arabia can help in effectively controlling these pathogens.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0254170PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8297770PMC
July 2021

First Report of Fusarium Root and Stem Rot Caused by Fusarium oxysporum f. sp. radicis-cucumerinum on Greenhouse Cucumbers in Saudi Arabia.

Plant Dis 2021 Apr 26. Epub 2021 Apr 26.

Department of Plant Protection, College of Food and Agricultural Sciences, King Saud University, Kingdom of Saudi Arabia, Riyadh, Saudi Arabia;

Cucumber (Cucumis sativus L.) is an important vegetable crop in Saudi Arabia. During May 2018, 45 - 60% of 5-month-old cucumber plants showed symptoms of a previously unknown wilt in commercial greenhouses around Al Kharj area of Riyadh region. Symptoms consisted of crown and root rot, wilting and stem disintegration, along with yellowish brown to brown external discoloration extended throughout the affected tissues. As the disease progressed, a pinkish-orange mycelial growth was often observed at the basis of affected stems while vessels were discolored. Subsequently, the affected plants were collapsed and died. Crown, stem, and root fragments (4 × 4 mm) were cut from symptomatic tissues, surface sterilized in 2.5% NaOCl, cultured on potato dextrose agar (PDA) with 25 mg/liter of streptomycin sulfate, and incubated at 26°C in darkness for 6 days. Single-spored cultures produced white mycelium with pink, white, or purple pigmentation in the center. The mycelium produced sporodochia. Macroconidia were mainly slightly curved with three to five septa. Microconidia were single-celled oval and produced on short lateral phialides. Chlamydospores were single or in short chains. Morphologically, the isolated fungus was characterized as Fusarium oxysporum (Leslie and Summerell 2006). To further confirm the fungus identification, DNA was extracted from a single-spored culture. Three different fungal nuclear regions of internal transcribed spacer (ITS), elongation factor 1-α, (TEF1-α) and the second largest subunit of DNA-directed RNA polymerase II (rpb2) with the following primers: ITS4 and ITS5 (White et al. 2017), EF-1 and EF-2 (O'Donnell et al. 2008), and fRPB2-5F and fRPB2-7cR (Liu et al. 1999), respectively. The ITS, TEF1-α, and rpb2 sequences of the isolate FCKSU17 were submitted to GenBank (MT232918, MW471131, and MW449833 respectively). Phylogenetic analysis based on the alignment of the ITS, TEF1-α, and rpb2 sequences using MEGA7 placed this strain in the F. oxysporum clade. To confirm the forma specialis radicis-cucumerinum, amplification with the specific primers ForcF1/ForcR2 was conducted (Lievens et al. 2007). The amplified fragment (∼ 250-bp) was sent for sequencing, and the sequence was submitted to GenBank (MW471132). BLASTn analysis of the sequences showed 100% identity with F. oxysporum radicis-cucumerinum (KP746408). To fulfill Koch's postulates, pathogenicity test was conducted on 7-day-old plants of cucumber cultivar Beit Alpha grown into pots filled with soil mix (2:1 sandy loam-peat moss, vol/vol). The plants were inoculated through drenching with 100 ml of conidial suspension in sterile distilled water (106 spores/ml) per pot. Control plants were treated with sterile distilled water. Each treatment included 10 replicates (pots), with two plants per pot. The pathogenicity test was repeated once. Cucumber plants inoculated with the fungus showed early wilting symptoms within the first 2 weeks post inoculation. At the 6th week post inoculation, 90 to 100% of the inoculated plants developed typical symptoms. No symptoms were observed on the control plants. The pathogen was successfully re-isolated from the inoculated wilted plants and identified morphologically. To our knowledge, this is the first report of F. oxysporum f.sp. radicis-cucumerinum on cucumber in Saudi Arabia. It is recommended that preventive management should be considered as this disease may cause significant economic losses on cucumbers in Saudi Arabia.
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http://dx.doi.org/10.1094/PDIS-01-21-0122-PDNDOI Listing
April 2021

Molluscicidal activity of cardiac glycosides isolated from Adenium obesum.

Pest Manag Sci 2019 Oct 1;75(10):2770-2775. Epub 2019 Apr 1.

Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.

Background: Terrestrial mollusks are one of most important agricultural pests worldwide. Natural phytochemicals have an extended history as a source of pesticides. This study was planned to isolate molluscicidal active compounds from the stems of Adenium obesum.

Results: The benzene-soluble fraction of the hydroethanolic extract displayed the most potent molluscicidal activity against Monacha obstructa among different solvent fractions with a median lethal dose (LD ) of 4.91 µg g body weight (bw). The bioactivity-guided chemical exploration of the benzene-soluble fraction led to the isolation of two known cardiac glycosides, cerberin and neriifolin which showed significant molluscicidal activity with LD values of 5.39 and 4.3 µg g bw, respectively.

Conclusion: Isolation of the cardiac glycoside neriifolin from A. obesum and the molluscicidal activity of cerberin and neriifolin against terrestrial snails are reported for the first time. © 2019 Society of Chemical Industry.
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http://dx.doi.org/10.1002/ps.5388DOI Listing
October 2019

Mitochondrial Molecular Markers for Resistance to Bayoud Disease in Date Palm.

Methods Mol Biol 2017 ;1638:273-282

Faculty of Agriculture, Plant Pathology Department, Alexandria University, Alexandria, Egypt.

Bayoud disease, caused by Fusarium oxysporum f. sp. albedinis, is a very serious and destructive disease to date palm. Screening of date palm germplasm for resistance to bayoud disease is a crucial step to avoid or alleviate the disease consequences. Fortunately, it was discovered that there are two mitochondrial plasmid-like DNA molecules associated with susceptibility or resistance to bayoud disease. In this chapter, we present a fast, simple, and reliable technique to screen date palm germplasm for the presence of these mitochondrial molecular markers associated with susceptibility or resistance to bayoud.
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http://dx.doi.org/10.1007/978-1-4939-7159-6_22DOI Listing
April 2018

Characterization of Novel Trichoderma asperellum Isolates to Select Effective Biocontrol Agents Against Tomato Fusarium Wilt.

Plant Pathol J 2015 Mar 31;31(1):50-60. Epub 2015 Mar 31.

Department of Plant Protection, College of Food and Agricultural Sciences, King Saud University, Kingdom of Saudi Arabia.

The use of novel isolates of Trichoderma with efficient antagonistic capacity against Fusarium oxysporum f. sp. lycopersici (FOL) is a promising alternative strategy to pesticides for tomato wilt management. We evaluated the antagonistic activity of 30 isolates of T. asperellum against 4 different isolates of FOL. The production of extracellular cell wall degrading enzymes of the antagonistic isolates was also measured. The random amplified polymorphic DNA (RAPD) method was applied to assess the genetic variability among the T. asperellum isolates. All of the T. asperellum isolates significantly reduced the mycelial growth of FOL isolates but the amount of growth reduction varied significantly as well. There was a correlation between the antagonistic capacity of T. asperellum isolates towards FOL and their lytic enzyme production. Isolates showing high levels of chitinase and β-1,3-glucanase activities strongly inhibited the growth of FOL isolates. RAPD analysis showed a high level of genetic variation among T. asperellum isolates. The UPGMA dendrogram revealed that T. asperellum isolates could not be grouped by their anta- gonistic behavior or lytic enzymes production. Six isolates of T. asperellum were highly antagonistic towards FOL and potentially could be used in commercial agriculture to control tomato wilt. Our results are consistent with the conclusion that understanding the genetic variation within Trichoderma isolates and their biochemical capabilities are required for the selection of effective indigenous fungal strains for the use as biocontrol agents.
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http://dx.doi.org/10.5423/PPJ.OA.09.2014.0087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4356605PMC
March 2015

Comparative Analysis of Defense Responses in Chocolate Spot-Resistant and -Susceptible Faba Bean (Vicia faba) Cultivars Following Infection by the Necrotrophic Fungus Botrytis fabae.

Plant Pathol J 2014 Dec 15;30(4):355-66. Epub 2014 Dec 15.

Department of Plant Protection, College of Food and Agricultural Sciences, King Saud University, Kingdom of Saudi Arabia. Plant Pathology Institute, Agriculture Research Center (ARC), Egypt.

In this study, resistance responses were investigated during the interaction of Botrytis fabae with two faba bean cultivars expressing different levels of resistance against this pathogen, Nubaria (resistant) and Giza 40 (susceptible). Disease severity was assessed on leaves using a rating scale from 1 to 9. Accumulation levels of reactive oxygen species (ROS), lipid peroxidation and antioxidant enzymes (superoxide dismutase, catalase and ascorbate peroxidase) were measured in leaf tissues at different times of infection. The expression profiles of two pathogenesis-related proteins (PRPs) encoded by the genes PR-1 and β-1,3-glucanase were also investigated using reverse transcription RT-PCR analysis. The accumulation of these defense responses was induced significantly in both cultivars upon infection with B. fabae compared with un-inoculated controls. The resistant cultivar showed weaker necrotic symptom expression, less ROS accumulation, a lower rate of lipid peroxidation and higher activity of the enzymatic ROS scavenging system compared with susceptible cultivar. Interestingly, ROS accumulated rapidly in the resistant leaf tissues and peaked during the early stages of infection, whereas accumulation was stronger and more intense in the susceptible tissues in later stages. Moreover, the response of the resistant cultivar to infection was earlier and stronger, exhibiting high transcript accumulation of the PR genes. These results indicated that the induction of oxidant/antioxidant responses and the accumulation of PRPs are part of the faba bean defense mechanism against the necrotrophic fungus B. fabae with a different intensity and timing of induction, depending on the resistance levels.
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http://dx.doi.org/10.5423/PPJ.OA.06.2014.0050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262288PMC
December 2014

Genetic diversity among late blight resistant and susceptible potato genotypes.

Saudi J Biol Sci 2010 Apr 6;17(2):133-8. Epub 2010 Feb 6.

Plant Pathology Dept., Faculty of Agriculture, Alexandria University, Egypt.

RAPD polymerase chain reaction analysis was used to study the genetic diversity among a wild potato variety Solanum demissum (very resistant to late blight) and six potato cultivars (Hanna, Lady-Olympia, Lady-Rosetta, Spunta, Diamant and Cara) varied in their resistance to Phytophthora infestans. Cluster analysis of six potato genotypes showed that, all tested genotypes were separated into two clusters (1 and 2). Cluster 1, included only the wild potato variety (S. demissum), whereas cluster 2 divided into two groups (G1 and G2). Late blight high resistant cultivars Hanna and Cara were grouped in G1. Group 2 included the moderate resistant cultivar Spunta and the susceptible cultivars Diamant, Lady-Rosetta and Lady-Olympia. The potato cultivars that showed highest genetic similarity to the wild potato variety were the resistant cultivars Hanna and Cara. Lowest genetic similarity was obtained with the susceptible cultivars Lady-Rosetta, Diamant and Lady-Olympia. RAPD primer K17 yielded a band with molecular weight of 936 bp found in all susceptible potato cultivars (Lady-Rosetta, Lady-Olympia and Diamant). On the other hand, band with molecular weight of 765 bp were detected in the wild potato and the resistant cultivars Hanna and Cara. Results of this study suggested that, the RAPD marker technique could be beneficial for revealing the genetic variability of different genotypes of potato varied in their resistibility to late blight.
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http://dx.doi.org/10.1016/j.sjbs.2010.02.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3730802PMC
April 2010
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