Identification, distribution and incidence of viruses in field-grown cucurbit crops of Iran

A survey of viruses in the major cucurbit-growing areas of 17 provinces in Iran was conducted in 2005 and 2006. A total of 1699 leaf samples were collected from melon, squash, cucumber and watermelon plants showing various virus-like symptoms. Screening for 11 cucurbit viruses by double-antibody sandwich ELISA (DAS-ELISA) or RT-PCR, found that 71% of the samples were infected by at least one virus, of which Cucurbit aphid-borne yellows virus (CABYV) was the most common overall, occurring in 49, 47, 40, and 33% of cucumber, squash, melon, and watermelon samples respectively. The second most common virus on melon and watermelon was Watermelon mosaic virus (WMV) (incidence 30–33%); on cucumber, Cucumber mosaic virus (CMV)(33%); and on squash, Zucchini yellow mosaic virus (ZYMV)(38%). To our knowledge, this is the first report of Melon necrotic spot virus (MNSV) and Zucchini yellow fl eck virus (ZYFV) in Iran. Mixed infections occurred in 49% of symptomatic samples. Mixed infections were relatively frequent in squash (58%) and melon (55%). The most frequent double infections were WMV+CABYV and ZYMV+CABYV in melon, squash and cucumber, followed by WMV+ZYMV. In watermelon, the most frequent double infection was WMV+ZYMV, followed by WMV+CABYV. The high frequency of CABYV, WMV and ZYMV in the samples assayed on all four cucurbit crops and in all areas surveyed, as well as the detection of Watermelon chlorotic stunt virus (WmCSV) and Cucumber vein yellowing virus (CVYV) in northern and southern Iran, suggest that these viruses represent a potential threat to cucurbit crops in Iran

The Spread of Tomato Yellow Leaf Curl Virus from the Middle East to the World

The ongoing global spread of Tomato yellow leaf curl virus (TYLCV; Genus Begomovirus, Family Geminiviridae) represents a serious looming threat to tomato production in all temperate parts of the world. Whereas determining where and when TYLCV movements have occurred could help curtail its spread and prevent future movements of related viruses, determining the consequences of past TYLCV movements could reveal the ecological and economic risks associated with similar viral invasions. Towards this end we applied Bayesian phylogeographic inference and recombination analyses to available TYLCV sequences (including those of 15 new Iranian full TYLCV genomes) and reconstructed a plausible history of TYLCV's diversification and movements throughout the world. In agreement with historical accounts, our results suggest that the first TYLCVs most probably arose somewhere in the Middle East between the 1930s and 1950s (with 95% highest probability density intervals 1905–1972) and that the global spread of TYLCV only began in the 1980s after the evolution of the TYLCV-Mld and -IL strains. Despite the global distribution of TYLCV we found no convincing evidence anywhere other than the Middle East and the Western Mediterranean of epidemiologically relevant TYLCV variants arising through recombination. Although the region around Iran is both the center of present day TYLCV diversity and the site of the most intensive ongoing TYLCV evolution, the evidence indicates that the region is epidemiologically isolated, which suggests that novel TYLCV variants found there are probably not direct global threats. We instead identify the Mediterranean basin as the main launch-pad of global TYLCV movements

Ongoing geographical spread of Tomato yellow leaf curl virus

Tomato yellow leaf curl virus (TYLCV) seriously impacts tomato production throughout tropical and sub-tropical regions of the world. It has a broad geographical distribution and continues to spread to new regions in the Indian and Pacific Oceans including Australia, New Caledonia and Mauritius. We undertook a temporally-scaled, phylogeographic analysis of all publicly available, full genome sequences of TYLCV, together with 70 new genome sequences from Australia, Iran and Mauritius. This revealed that whereas epidemics in Australia and China likely originated through multiple independent viral introductions from the East-Asian region around Japan and Korea, the New Caledonian epidemic was seeded by a variant from the Western Mediterranean region and the Mauritian epidemic by a variant from the neighbouring island of Reunion. Finally, we show that inter-continental scale movements of TYLCV to East Asia have, at least temporarily, ceased, whereas long-distance movements to the Americas and Australia are probably still ongoing

The status of Cucumber vein yellowing virus in Iran

Yellowing symptoms of greenhouse- and open field-grown cucurbit crops are becoming increasingly important in many cucurbit growing regions of the world, and particularly in Iran. A survey was conducted from 2011 to 2012 in eight major cucurbit growing regions in Iran. Yellowing and specifically vein clearing symptoms were observed in many cucumber plants grown in greenhouses and open fields, suggesting the presence of Cucumber vein yellowing virus (CVYV, genus Ipomovirus, family Potyviridae). The identification of CVYV was carried out with a specific triple-antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) and reverse transcription (RT)-PCR. CVYV was detected in 42% of the collected samples, in all surveyed provinces, except Bushehr. CVYV was also detected in melon and cucumber crops grown in open fields. These results indicate that CVYV is widely distributed on these two cucurbit species in the major cucumber growing areas of Iran. CVYV positive samples were also tested, using DAS-ELISA, for the presence of Cucurbit chlorotic yellows virus (CCYV) and Cucurbit yellow stunting disorder virus (CYSDV), two criniviruses reported previously to occur in Iran. Double or triple infections of CCYV and CYSDV occurred in 49 of 166 of the CVYV-infected plants. The CVYV and CCYV combined infections were more prevalent than CVYV and CYSDV combined infections. TAS-ELISA positive samples were used to mechanically inoculate healthy cucumber plants, and mild vein yellowing was observed on the inoculated leaves. Identical symptoms were also observed on whitefly inoculated healthy cucumber plants. The presence of CVYV in mechanically and whitefly inoculated plants was confirmed by TAS-ELISA and RT-PCR. Sequence analysis revealed that the Iranian isolate of CVYV was more closely related to Spanish isolates than to isolates from Jordan. Phylogenetic analysis showed that CVYV isolates can be divided into two phylogenetic groups (I and II). Despite the close vicinity of Jordan to Iran, the Iranian CVYV isolate clustered with Spanish isolates in group I and not with the Jordanian isolates of group II

Serological and molecular identification of Tomato yellow leaf curl virus in Khuzestan province of Iran

A survey was conducted from 2006 to 2007 to identify the causal agent of leaf curling of tomato in eight major tomato-growing areas of Khuzestan province in southwest of Iran. Tomato leaf samples showing leaf curling, yellowing, and stunting were collected and screened for the presence of Tomato yellow leaf curl virus (TYLCV) by TAS-ELISA. Further confi rmation was completed using graft transmission onto healthy tomato plants and PCR. Results confi rmed that TYLCV is a causal agent of tomato yellow leaf curl disease (TYLCD) and is widely distributed in all the major tomato growing areas in southwest of Iran. The nucleotide sequences of the coat protein (CP) gene of four isolates (Dezfoul, Shoush, Behbahan, and Ramhormoz) were determined and deposited in GenBank (EF199814-7). Phylogenetic analysis of the CP gene further showed that all four Iranian isolates have very close relationship and formed a Compact cluster together with previously sequenced Iranian TYLCV isolates

Slow light tunability in photonic crystals by defect layers

In present study, the effect of different defect layer refractive indices and thicknesses on group velocity has been studied in one-dimensional photonic crystal. It is found that the increase of refractive index, number of defects and defect layer thickness will induce the decrease of group velocity. Taking advantage of these results, a novel technique has been introduced to tune and control the slowing light in photonic crysta