Squash leaf curl virus (SLCV): a serious disease threatening cucurbits production in Palestine

Barcoding of Plant Viruses with Circular Single-Stranded DNA Based on Rolling Circle Amplification

The experience with a diagnostic technology based on rolling circle amplification (RCA), restriction fragment length polymorphism (RFLP) analyses, and direct or deep sequencing (Circomics) over the past 15 years is surveyed for the plant infecting geminiviruses, nanoviruses and associated satellite DNAs, which have had increasing impact on agricultural and horticultural losses due to global transportation and recombination-aided diversification. Current state methods for quarantine measures are described to identify individual DNA components with great accuracy and to recognize the crucial role of the molecular viral population structure as an important factor for sustainable plant protection.

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.

Molecular characterization of watermelon chlorotic stunt virus (WmCSV) from Palestine

The incidence of watermelon chlorotic stunt disease and molecular characterization of the Palestinian isolate of Watermelon chlorotic stunt virus (WmCSV-[PAL]) are described in this study. Symptomatic leaf samples obtained from watermelon Citrullus lanatus (Thunb.), and cucumber (Cucumis sativus L.) plants were tested for WmCSV-[PAL] infection by polymerase chain reaction (PCR) and Rolling Circle Amplification (RCA). Disease incidence ranged between 25%-98% in watermelon fields in the studied area, 77% of leaf samples collected from Jenin were found to be mixed infected with WmCSV-[PAL] and SLCV. The full-length DNA-A and DNA-B genomes of WmCSV-[PAL] were amplified and sequenced, and the sequences were deposited in the GenBank. Sequence analysis of virus genomes showed that DNA-A and DNA-B had 97.6%-99.42% and 93.16%-98.26% nucleotide identity with other virus isolates in the region, respectively. Sequence analysis also revealed that the Palestinian isolate of WmCSV shared the highest nucleotide identity with an isolate from Israel suggesting that the virus was introduced to Palestine from Israel.