Frequent migration of introduced cucurbit-infecting begomoviruses among Middle Eastern countries.

BACKGROUND: In the early 2000s, two cucurbit-infecting begomoviruses were introduced into the eastern Mediterranean basin: the Old World Squash leaf curl virus (SLCV) and the New World Watermelon chlorotic stunt virus (WmCSV). These viruses have been emerging in parallel over the last decade in Egypt, Israel, Jordan, Lebanon and Palestine. METHODS: We explored this unique situation by assessing the diversity and biogeography of the DNA-A component of SLCV and WmCSV in these five countries. RESULTS: There was fairly low sequence variation in both begomovirus species (SLCV π = 0.0077; WmCSV π = 0.0066). Both viruses may have been introduced only once into the eastern Mediterranean basin, but once established, these viruses readily moved across country boundaries. SLCV has been introduced at least twice into each of all five countries based on the absence of monophyletic clades. Similarly, WmCSV has been introduced multiple times into Jordan, Israel and Palestine. CONCLUSIONS: We predict that uncontrolled movement of whiteflies among countries in this region will continue to cause SLCV and WmCSV migration, preventing strong genetic differentiation of these viruses among these countries.

Diagnosis and control of cereal viruses in the Middle East.

Middle Eastern countries are major consumers of small grain cereals. Egypt is the biggest bread wheat producer with 7.4 million tons (MT) in 2007, but at the same time, it had to import 5.9 MT. Jordan and Israel import almost all the grains they consume. Viruses are the major pathogens that impair grain production in the Middle East, infecting in some years more than 80% of the crop. They are transmitted in nonpersistent, semipersistent, and persistent manners by insects (aphids, leafhoppers, and mites), and through soil and seeds. Hence, cereal viruses have to be controlled, not only in the field but also through the collaborative efforts of the plant quarantine services inland and at the borders, involving all the Middle Eastern countries. Diagnosis of cereal viruses may include symptom observation, immunological technologies such as ELISA using polyclonal and monoclonal antibodies raised against virus coat protein expressed in bacteria, and molecular techniques such as PCR, microarrays, and deep sequencing. In this chapter, we explore the different diagnoses, typing, and detection techniques of cereal viruses available to the Middle Eastern countries. We highlight the plant quarantine service and the prevention methods. Finally, we review the breeding efforts for virus resistance, based on conventional selection and genetic engineering.

Oligonucleotide microarray-based detection and genotyping of Plum pox virus.

Plum pox virus (PPV) is the most damaging viral pathogen of stone fruits. The detection and identification of its strains are therefore of critical importance to plant quarantine and certification programs. Existing methods to screen strains of PPV suffer from significant limitations such as the simultaneous detection and genotyping of several strains of PPV in samples infected with different isolates of the virus. A genomic strategy for PPV screening based on the viral nucleotide sequence was developed to enable the detection and genotyping of the virus from infected plant tissue or biological samples. The basis of this approach is a long 70-mer oligonucleotide DNA microarray capable of simultaneously detecting and genotyping PPV strains. Several 70-mer oligonucleotide probes were specific for the detection and genotyping of individual PPV isolates to their strains. Other probes were specific for the detection and identification of two or three PPV strains. One probe (universal), derived from the genome highly conserved 3' non-translated region, detected all individual strains of PPV. This universal PPV probe, combined with probes specific for each known strain, could be used for new PPV strain discovery. Finally, indirect fluorescent labeling of cDNA with cyanine after cDNA synthesis enhanced the sensitivity of the virus detection without the use of the PCR amplification step. The PPV microarray detected and identified efficiently the PPV strains in PPV-infected peach, apricot and Nicotiana benthamiana leaves. This PPV detection method is versatile, and enables the simultaneous detection of plant pathogens.