Citrus tristeza virus (CTV, Genus Closterovirus, Family Closteroviridae), is the most destructive and economically important viral disease limiting commercial citrus production worldwide. This study was conducted during 2016-2017 growing seasons in order to identify the prevalence of different variants of CTV along the Syrian coast. Citrus samples were collected from different locations, and tested for the presence of Citrus tristeza virus by using TBIA test and using polyclonal antisera. Three CTV Isolates were used as scions from different locations and grafted to different citrus indicators, such as Mexican lime, sour orange and sweet orange varieties grafted on sour orange rootstock. Results showed that different symptoms were produced by the different isolates on the same citrus indicators. Symptoms produced showed various mosaic, chlorosis, leaf malformation, leaf curling, and stunting levels. Moreover, no symptoms were observed on stems of the indicator plants such as stem pitting and quick decline, up to one year after inoculation. These results suggest the possibility of having two CTV variants present along the Syrian coast: a yellowing strain and a mild strain.
Ghanem, H.M., E.H. Akel, Q.A. Al-Rhayeh and I.D. Ismail. 2021. Induction of Systemic Resistance in Tomato Plants Against Tomato yellow leaf curl virus in Protected Cultivation Using a Local Bacterial Isolate of Bacillus subtilis. Arab Journal of Plant Protection, 39(4): 289-295. https://doi.org/10.22268/AJPP-039.4.289295 This study was conducted at the Agricultural Scientific Research Center in Lattakia Governorate in a plastic house during the 2020/2021 growing season to evaluate the efficiency of the native bacterial isolate B.Ra.217 of Bacillus subtilis, in reducing infection of tomato plants with Tomato yellow leaf curl virus (TYLCV), by treating tomato seeds and later watering the seedlings with a suspension of the tested bacteria at a concentration of 1x109 /ml, and then measuring incidence (%) and severity of virus infection, and estimating peroxidase enzyme activity. The results showed that 30 days after inoculation with tomato leaf curl virus, a decrease in virus infection rate and severity in virus-infected and bacteria-treated plants compared with virus-infected and untreated control plants was observed. The reduction in disease incidence and severity of infection reached 26.67% and 34.28%, respectively, with significant differences between the treatments. In addition, the activity of peroxidase enzyme 7 days after infection with the virus showed an increase in plants treated with bacteria only (0.1342 μmol/mg) and those treated with bacteria and virus-infected (0.0913 μmol/mg), compared with the healthy control plants (0.0958 μmol/mg), and virus-infected and untreated with bacteria (0.0570 µmol/mg). The results also showed 15 days after infection that the enzyme activity was higher in plants treated with bacteria only (0.1592 µmol/mg) compared with the healthy control (0.1415 µmol/mg) with significant differences, and also the differences were significant with the untreated infected plants (0.1002 µmol/mg), and with inoculated and treated plants (0.1372 µmol/mg). Thus, this bacterial isolate may have an important applied role in enhancing tomato plant resistance to the virus and consequently reducing its damage. Keywords: Bacillus subtilis B.Ra.217, TYLCV, peroxidase, incidence, severity of infestation, tomato plant
Hamdan, R.S., I.D. Ismail and I. Akel. 2021. Effect of Tomato Yellow Leaf Curl Virus Infection on Some Growth Indicators of Pepper Hybrids Grown Under Plastic House Conditions in Lattakia Governorate, Syria. Arab Journal of Plant Protection, 39(4): 309-316. https://doi.org/10.22268/AJPP-39.4.309316 This study aimed to evaluate the effect of Tomato yellow leaf curl virus (TYLCV) infection on some growth parameters of several pepper hybrids grown under protected cultivation along the Syrian coast. Four pepper hybrids (Capsicum annum) were tested, two hot (Lahab, Sirad) and two sweet (Nevada, Dallas) peppers. The research was carried out during the 2020-2021 growing season in a plastic house at the Agriculture Scientific Research Center in Lattakia, using a randomized complete block design, with 8 treatments, three replicates and 5 plants per replicate. The results obtained showed that the sweet pepper hybrids (Nevada, Dallas) were more sensitive to infection with Tomato yellow leaf curl virus than the hot pepper hybrids (Lahab, Sirad), without significant differences among them. The pepper hybrid Nevada did not show any apparent symptoms, and the effect of the virus on some growth parameters (number flowers, flower setting, and the leaf surface area) was evident in comparison with other hybrids, but the differences were not significant. The Dallas, Sirad and Lahab pepper hybrids showed visible symptoms in response to infection with infection rate of 93.33%, 80% and 80%, respectively. The effect of virus infection on the growth parameters of these hybrids was variable. The reduction in the flowers number of Nevada, Dallas, Cirad and Lahab after 45 days of infection was 33%, 31.10%, 10.23% and 5.07%, respectively, and also with a reduction in the number of flowers setting of 77.39%, 20.87%, 23.33% and 66.68%, respectively. The same was true for the leaf surface area, where reduction rate for the Nevada, Dallas, Sirad and Lahab hybrids 30 days after infection was 48.17%, 53.06%, 16.45% and 36.6%, respectively. Keywords: Tomato yellow leaf curl virus, pepper hybrids, growth parameter, host resistance, protected agriculture.
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