Publications
2008
Cucurbit yellow stunting disorder virus (CYSDV) is an emerging virus causing significant yield losses in cucurbits. Simple but reliable detection and quantification methods are important tools for disease management. In susceptible germplasm, CYSDV was detected 5 days postinoculation (dpi) by reverse transcriptase polymerase chain reaction (RT-PCR) or by tissue blot immunoassay (TBIA), and 8–9 dpi by dot blot immunoassay (DBIA) or enzyme-linked immunosorbent assay (ELISA). For CYSDV quantification, real-time RT-PCR was the most sensitive method and gave the best linear range of detection, over four orders of magnitude as compared to approximately two orders of magnitude for DBIA and nucleic acid hybridization. Read more…
Tomato production in the Mediterranean region and elsewhere is under constant threat of the whitefly-transmitted begomoviruses that cause Tomato yellow leaf curl disease (TYLCD). Sequencing has indicated that the generic ‘TYLCV’ includes a large number of viruses and strains. We studied the distribution of the tomato yellow leaf curl disease-associated viruses in Egypt, Israel, Jordan and Lebanon. Two simple and reliable multiplex PCR protocols (mPCR) were developed that allowed the detection of Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) species, in addition to Tomato yellow leaf curl virus-Mud (TYLCV-Mld) strain. PCR products were sequenced to confirm their identity. Read more…
Larvae of the cedar web-spinning sawfly, Cephalcia tannourinensis Chevin (Hymenoptera: Pamphiliidae), infected with a white fungus were collected from the Tannourine-Hadath El-Jebbeh cedar forest. Macro- and micro-morphological data based on the examination of colonies, conidiophores, and conidial shape of the fungus suggested a Beauveria species. Sequence analysis of the internal transcribed spacer regions of the isolated fungus showed that it is most closely related to isolates of B. bassiana Clade C. The present study showed that the isolated B. bassiana is a naturally occurring entomopathogenic fungus parasitizing the larvae of C. tannourinensis in Lebanon. Read more…
A Lebanese isolate of a Beauveria species originally isolated from a hymenopterous insect pest was found to be very effective against the pine processionary moth Thaumetopoea wilkinsoni. In laboratory bioassays, high mortality rates of the five larval stages were attained with spore concentrations of about 5000–50,000 spores/larva. The efficacy of kill on the first three larval stages was similar to the growth regulator diflubenzuron, but it was significantly higher on the fourth and fifth larval stages. Sequences of the DNA lyase gene and the EF-1α gene were used for molecular characterisation of this Beauveria isolate. Read more…
2007
Tomato yellow leaf curl virus (TYLCV), a whitefly transmitted geminivirus, is the major limiting factor for tomato production in many countries in the Middle East, Europe, Africa and was reported in North and South America. Development of resistant varieties represents the most economical management measure. DNA sequences of the six major strains of TYLCV reported in the Middle East and Europe were aligned and sequences with more than 21 conserved nucleotides were determined. Three primer pairs were designed and used in PCR assays to amplify three overlapping regions of 240, 355 and 505bps. The amplicons were cloned in pHELLSGATE 2 using BP and LR clonase. This protocol allows the insertion, in one step, of the genes of interest in sense and antisense orientation with an intron in between. Read more…
Lebanese tomatoes are valued for their taste and large fruit size. However, they are susceptible to a number of diseases, the most important is Tomato yellow leaf curl virus (TYLCV), which leads to losses close to 100%. TYLCV is considered the bottleneck for tomato production along the Lebanese coast and in many other countries in the Middle East, Europe and Africa. Lebanese tomato landraces were crossed with four parents: Lines Ih 902 and GF 13 (S. habrochaites) which carry dominant monogenic resistances to TYLCV, Fusarium oxysporum fsp. lycopercisi (FOL) race 2 and Verticillium wilt race 1.; Line GS 16 (S. chilense), which carries a major gene of resistance to TYLCV with partial dominance; Line 197 (S. peruvianum) which is believed to carry a few recessive genes that impart resistance to TYLCV. Read more…
Fusarium vascular wilt, caused by Fusarium oxysporum f. sp. lycopersici, affects tomatoes worldwide. Development of resistant varieties of tomato would constitute an economically and environmentally sound approach for the management of this disease. Resistance genes to F. oxysporum f. sp. lycopersici race 1 (I-1 gene) and race 2 (I-2 gene) were mapped to chromosome 11. The I-2 gene cluster includes one functional copy and six nonfunctional homologs of the I-2 gene. This report describes the design of primers based on the functional gene copy and the development of a multiplex polymerase chain reaction (PCR)-based method that has the ability to differentiate I-2 genotypes from genotypes without the I-2 gene. In these trials, 39 of the 40 genotypes tested with known reactions to race 2 gave the expected results. Read more…
2006
Tomato seedlings showing leaf curl and yellowing symptoms characteristic of Tomato yellow leaf curl virus (TYLCV) were brought to the university laboratory from a commercial tomato greenhouse located in the Damour coastal area, south of Beirut, Lebanon. They were first tested using polymerase chain reaction (PCR) to ascertain their infection by TYLCV and then they were used in a trial to evaluate resistance of three local accessions of tomato to TYLCV, the major limiting factor to tomato production in Lebanon. Whiteflies (Bemisia tabaci), reared on broccoli for several generations, were allowed an acquisition access period of 48 h on tomato seedlings putatively infected with TYLCV and then were transferred to test plants at an average of 40 to 60 whiteflies per tomato seedling at the first-true leaf stage for an inoculation feeding period of 3 days. Read more…