Publications by authors named "Tesfamariam Mekete"

6 Publications

  • Page 1 of 1

Influence of Root Exudates and Soil on Attachment of to .

J Nematol 2017 Sep;49(3):304-310

Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611.

The bacterium is a parasite of root-knot nematodes ( spp.). Endospores of attach to the cuticle of second-stage juveniles (J2) and subsequently sterilize infected females. When encumbered by large numbers of spores, juveniles are less mobile and their ability to infect roots is reduced. This study looked at different factors that influence spore attachment of to the root-knot nematode . Pretreatment of J2 with root exudates of eggplant ( cv. Black beauty) reduced spore attachment compared with pretreatment with phosphate-buffered saline (PBS), suggesting that the nematode surface coat was altered or the spore recognition domains on the nematode surface were blocked. Spore attachment was equally reduced following exposure to root exudates from both host and nonhost plants for , indicating a common signal that affects spore attachment. Although phytohormones have been shown to influence the lipophilicity of the nematode surface coat, auxins and kinetins did not affect spore attachment compared with PBS. Root exudates reduced spore attachment more in sterilized soil than in natural soil. Sterilization may have eliminated microbes that consume root exudates, or altered the chemical components of the soil solution or root exudates. Root exudates caused a greater decrease in spore attachment in loamy sand than in a sandy loam soil. The sandy loam had higher clay content than the loamy sand, which may have resulted in more adsorption of compounds in the root exudates that affect spore attachment. The components of the root exudates could have also been modified by soil type. The results of this study demonstrate that root exudates can decrease the attachment of endospores to root-knot nematodes, indicating that when these nematodes enter the root zone their susceptibility to spore attachment may decrease.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5644923PMC
September 2017

Association analysis of resistance to cereal cyst nematodes () and root lesion nematodes ( and ) in CIMMYT advanced spring wheat lines for semi-arid conditions.

Breed Sci 2016 Dec 25;66(5):692-702. Epub 2016 Oct 25.

Grains Research & Development Corporation (GRDC) , 4/4 National Circuit Barton 2600 ACT , Australia.

To identify loci linked to nematode resistance genes, a total of 126 of CIMMYT advanced spring wheat lines adapted to semi-arid conditions were screened for resistance to , , and , of which 107 lines were genotyped with 1,310 DArT. Association of DArT markers with nematode response was analyzed using the general linear model. Results showed that 11 markers were associated with resistance to (pathotype Ha21), 25 markers with resistance to , and 9 significant markers were identified to be linked with resistance to . In this work we confirmed that chromosome 4A (~90-105 cM) can be a source of resistance to as has been recently reported. Other significant markers were also identified on chromosomal regions where no resistant genes have been reported for both nematodes species. These novel QTL were mapped to chromosomes 5A, 6A, and 7A for ; on chromosomes 1A, 1B, 3A, 3B, 6B, 7AS, and 7D for ; and on chromosomes 1D, 2A, and 5B for and represent potentially new loci linked to resistance that may be useful for selecting parents and deploying resistance into elite germplasm adapted to regions where nematodes are causing problem.
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http://dx.doi.org/10.1270/jsbbs.15158DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5282747PMC
December 2016

Phasmarhabditis bonaquaense n. sp. (Nematoda: Rhabditidae), a new slug-parasitic nematode from the Czech Republic.

Zootaxa 2016 Oct 31;4179(3):530-546. Epub 2016 Oct 31.

Biology Centre CAS, Institute of Entomology, Laboratory of entomopathogenic nematodes, Branišovská 1160/31, 370 05 České Budějovice, Czech Republic.; Email:

Phasmarhabditis bonaquaense n. sp. is described and illustrated from the body of Malacolimax tenellus, from the locality of České Švýcary near the village of Dobrá Voda, the Czech Republic. Females are characterized by a body length of 2349 (1878-2626) µm and a cupola shaped tail with a long hyaline hair-like tail tip. Extremely prominent papilla-like phasmids present. Males 1829 (1414-2121) µm long. Peloderan bursa with nine pairs of rays (papillae), 1/1/1/2/1/3. One non-paired apparent papilla-like structure located near the ventral appendage anterior to the cloaca. Prominent papilla-like phasmids located close to the tail tip. Small subunit (18S), ITS, and D2-D3 expansion segments of the large subunit of ribosomal DNA were used to analyze the phylogenetic relationships of sequenced species in the genus Phasmarhabditis and other closely related species. Phasmarhabditis bonaquaense n. sp. varied from other related nematodes both in morphological characterizations and phylogenetic analysis. The life cycle of the newly described species is not well known but it is probably a facultative, mollusc-parasitic nematode able to survive permanently in the saprobic phase on decaying organic matter.
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http://dx.doi.org/10.11646/zootaxa.4179.3.8DOI Listing
October 2016

First Report of Meloidogyne haplanaria Infecting Mi-Resistant Tomato Plants in Florida and Its Molecular Diagnosis Based on Mitochondrial Haplotype.

Plant Dis 2016 Jul 4;100(7):1438-1445. Epub 2016 Apr 4.

University of Florida, Institute of Food and Agricultural Sciences, Citrus Research & Education Center, Lake Alfred 33850.

Meloidogyne haplanaria is a species originally found infesting peanut in Texas and, more recently, in Arkansas. In this study, we confirmed the presence of M. haplanaria in Florida based on morphological and molecular characterization. This species was identified from a sample submitted for diagnosis collected from Mi-resistant tomato rootstock grown in Naples, FL. The major diagnostic criteria to distinguish M. haplanaria from other closely related root-knot nematode (RKN) species are based on morphological differences and host range tests, which are time consuming and labor intensive and require living or well-preserved specimens. In our study, we provide an easy diagnostic strategy to distinguish M. haplanaria from other RKN species based on amplification of two mitochondrial DNA regions. These regions span the intergenic spacer and part of the adjacent large subunit ribosomal RNA gene (lrDNA) and sequence polymorphisms in lrDNA revealed by the restriction pattern following digestion with the restriction enzymes HinfI and MnlI. A unique haplotype pattern, which has not been observed in any of the RKN species described thus far, was observed in M. haplanaria. The outcome of molecular analysis of M. haplanaria aligned with morphological measurement and characteristics as well as perineal pattern originally described for M. haplanaria.
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http://dx.doi.org/10.1094/PDIS-09-15-1113-REDOI Listing
July 2016

Neotobrilus nicsmolae n. sp. (Tobrilidae: Nematoda) and Chronogaster carolinensis n. sp. (Chronogasteridae: Nematoda) from Lake Phelps, North Carolina.

J Nematol 2013 Mar;45(1):66-77

Department of Biology and Marine Environmental Science, Elizabeth City State University, 1704 Weeksville Rd., Elizabeth City, NC.

Two new species, Neotobrilus nicsmolae n. sp. and Chronogaster carolinensis n. sp. are described from a small, acidic, temperate, natural lake in North Carolina. N. nicsmolae n. sp. comes close to three members of the genus reported from North America, N. filipjevi, N. longus, and N. hopei. However, N. nicsmolae is unique with in the genus in having a combination of characters: size smaller than 1,700 μm, shorter outer labial and cephalic setae, tail shorter than 250 μm, last ventromedian supplement close (about 5 μm) to cloacal opening, spicule length of 61 to 85 μm, flagelloid sperm, and possession of subterminal setae. Assessment of relationships among clades within the Triplonchida using DNA sequences of the D2D3 expansion segment of the LSU rDNA showed that the family Trichodoridae and the genus Tripyla were recovered as monophyletic. The genus Tobrilus was recovered as monophyletic in the neighbor-joining and maximum likelihood trees, but that was not so in the maximum-parsimony tree. The separation among genera of the Trichodoridae, i.e., Trichodorus and Paratrichodorus, was not clear-cut in all phylograms. Chronogaster carolinensis n. sp. in having one ventral mucro with no spine and vacuolated lateral glandular bodies comes close to C. typica and C. ethiopica but differs from all hitherto known species in a combination of characteristics: in having long cephalic setae, long stoma, crystalloid bodies, vacuolated lateral glandular bodies, and a tail terminus with blunt ventral mucro, and its lack of lateral line.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3625134PMC
March 2013

Plant-Parasitic Nematodes Are Potential Pathogens of Miscanthus × giganteus and Panicum virgatum Used for Biofuels.

Plant Dis 2011 Apr;95(4):413-418

Energy Biosciences Institute and Department of Crop Sciences University of Illinois, Urbana, 61801.

A survey of Miscanthus × giganteus and switchgrass plots throughout the midwestern and southeastern United States was conducted to determine the occurrence and distribution of plant-parasitic nematodes associated with these biofuel crops. During 2008, rhizosphere soil samples were collected from 24 Miscanthus × giganteus and 38 switchgrass plots in South Dakota, Iowa, and Illinois. Additional samples were collected from 11 Miscanthus × giganteus and 10 switchgrass plots in Illinois, Kentucky, Georgia, and Tennessee the following year. The 11 dominant genera recovered from the samples were Pratylenchus, Helicotylenchus, Xiphinema, Longidorus, Heterodera, Hoplolaimus, Tylenchorhynchus, Criconemella, Paratrichodorus, Hemicriconemoides, and Paratylenchus. Populations of Helicotylenchus, Xiphinema, and Pratylenchus were common and recorded in 90.5, 83.8, and 91.9% of the soil samples from Miscanthus × giganteus, respectively, and in 91.6, 75, and 83.3% of the soil samples from switchgrass, respectively. Prominence value (PV) (PV = population density × √frequency of occurrence/10) was calculated for the nematodes identified. Helicotylenchus had the highest PV (PV = 384) and was followed by Xiphinema (PV = 152) and Pratylenchus (PV = 72). Several of the nematode species associated with the two biofuels crops were plant parasites. Of these, Pratylenchus penetrans, P. scribneri, P. crenatus, Helicotylenchus pseudorobustus, Hoplolaimus galeatus, X. americanum, and X. rivesi are potentially the most damaging pests to Miscanthus × giganteus and switchgrass. Due to a lack of information, the damaging population thresholds of plant-parasitic nematodes to Miscanthus × giganteus and switchgrass are currently unknown. However, damage threshold value ranges have been reported for other monocotyledon hosts. If these damage threshold value ranges are any indication of the population densities required to impact Miscanthus × giganteus and switchgrass, then every state surveyed has potential for yield losses due to plant-parasitic nematodes. Specifically, Helicotylenchus, Xiphinema, Pratylenchus, Hoplolaimus, Tylenchorhynchus, Criconemella, and Longidorus spp. were all found to have population densities within or above the threshold value ranges reported for other monocotyledon hosts.
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http://dx.doi.org/10.1094/PDIS-05-10-0335DOI Listing
April 2011