الفهرس 
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Abstract
Thyme (Thymus vulgaris L.) belonging to family Lamiaceae, is an aromatic perennial herb with potential uses, which can be explored for safe and effective for human benefit. This herbal plant has many advantageously uses and numerous health benefits, it was used for many purposes as it has a great importance in the pharmaceutical industry, food uses and in antimicrobial drug products. Thyme was well known in Egypt as an economic crop since the ancient Egyptians.
Thyme is subjected to attack by various disease pathogens which frequently induce severe losses in its plantations. Seedling damping-off, root rot and wilt of thyme constitute a serious problem in most growing areas in Minia Governorate. Recent field observations have shown that these diseases are widely spread causing highly destructive loses.
This study was carried out between 2016 and 2020 to survey thyme damping-off, root rot and wilt diseases in two districts belonging to Minia Governorate, to isolate the associated pathogens, to identify and prove their pathogenicity, to apply some experiments in laboratory, green house and field to control this disease.
Resuits can be summarized as the following:
Thyme damping off, root rot/wilt is widely distributed in the three villages; Abbad Sharouna, Elshekh Zyad and Al Gindiah, under study. The percentages of diseased plants ranged between 12.1 to 15.2% and severity was 5 -7%.
Five isolates of Fusarium semitectum, F. solani(2 isolates), Fusarium sp (2 isolates)., Rhzoctonia solani(5 isolates), Macrophomina phaseolina (4 isolates), two isolates of either Mucor sp. and Rhizopus stolonifer and one isolate of either Alternaria sp., Aspergillus flavus, or Sclerotium sp. were isolated from naturally diseased thyme plants. The most dominant genus was Fusarium which presented the highest frequency (38.45%), followed by Rhizoctonia solani (19.23%) and Macrophomina phasiolina (15.38%). Also, The highest frequency of fungi was isolated from Al Gindiah village (46.15%), followed by Abbad Sharona village (34.62 %) and then El Shekh Zyad village (19.23%).
Pathogenicity test revealed that Fusarium semitectum, R. solani and M. phaseolina were the most destructive to seedlings and transplants, in the order named, causing 73.3, 50 and 33.3% seedling damping off and 36.0, 21.7 and 14.9% disease severity, respectively when thyme seeds were sowed in September, whereas the mixture of these three fungi induced 46.7% infection and 22.5% severity. When thyme transplants, 90 days old, were planted in November, the percentages of root rot/wilt incidence were 51.9 and 22.2 and 33.33%, and severity ranged between 12-7 and 21.6%. Transplanting thyme in April reduced the DI% to 40.7, 18.5 and 25.0% caused by Fusarium semitectum, R. solani and M. phaseolina, respectively and DS% ranged between 11.8-21.6%. In the same time, the number of survival plants was increased in plants transplanted in April (59.3 - 81.5%) if compared with that transplanted in November (49.0 – 78.0%).
Culture filtrates of Fusarium semitectum, R. solani and M. phaseolina significantly reduced the seed germimation to 23.3, 55.0 and 53.3%, respectively, comparing with the control (100%). Seedlings plume and radicle lengths and vigor index of growing thyme treated seeds with culture filtrates of the three tested fungi were significantly reduced when comparing with control treatment.
The culture filtrates of F. semitectum, R. solani and M. phasiocola application had negative effects on the growth of thyme plants produced from treated transplants. Immersing thyme transplants in prepared culture filtrates significantly reduced all plant parameters tested (plant height, number of branches, plant fresh and dry weights, number of leaves /plant, leaves fresh and dry weights.
Salicylic acid and ascorbic acid reduced the growth of all tested thyme root rot/wilt pathogens in vitro. The pathogens growth reduced significantly as the concentration of the two compounds was increased. Salicylic acid was the most effective compound in this respect, causing complete inhibition at 200 ppm for F. semitectum and R. solani and at 400 ppm for M. phasiolina followed by Ascorbic acid.
All tested concentrations of Cure – M 72%, and Rolex 50%, and Rezolex- Ex-T 50% caused significant reduction on the mycelial growth of the three tested fungi when comparing with the control treatment. The fungitoxic effect of all tested compounds increased with increasing the fungicide concentration up to the level that induced complete inhibition. All tested fungicides caused complete inhibition for fungal growth at 400 ppm, except Cure–M and Rolex which at 400 ppm caused 70.0 and 73.33% reduction to the F. semitectum and R. solani growth, respectively.
Common thyme (T. vulgaris) and Syrian (Origanum syriacum var. sinacum) were susceptible to infection by the different root rot/wilt pathogens with different degrees of infection. Fusarium semetichtum revealed the most pathogenic one followed by Macrophomina phaseolina then Rhizoctonia solani. Origanum syriacum var. sinacum indicates the highest degree of resistance to F. semitectum (35.5 % DI and 15.1% DS) in comparing to T vulgaris (46.6, % DI and 20.43 % DS). Whereas, this species, Origanum syriacum var. sinacum, showed statistically more susceptible (42.2 and 24.5% DI and 23.56 and 16.87 %DS to both M. phaseolina and R. solani, respectively, when comparing with the common thyme (31.1 and 19.97 DI, %, and 14.7 and 13.8% DS). All determined thyme parameters of the two species tested were significantly affected to infection with all three tested fungi (F. semetectum, R. sokani and M. phaseolina) in the both experimental seasons.
Fusarium semitectum, R. solani and M. phaseolina were able to attack Rosemary (Salvia rosmarinus), Sage (Salvia officinalis), chamomile (Matricaria chamomilla), marjoram (Origanum majorana) and Melissa (Melissa officinalis) with different degrees of infection. Sage and marjoram were the highest susceptible, followed by chamomile, then Melissa and rosemary plants which recorded slight infection.
Soil texture played an important role for disease control, the maximum infection with all tested fungi (27.75 and 32.4% in the 1st and 2nd seasons, respectively) and severity (12.21 and 15.0%) occurred in the raw Nile soil, heavy soil, 90 days after transplanting. The least disease incidence and severity occurred by any of the tested pathogens was observed when the loamy- sandy soil (lightly soil) was used. While, the percentages of disease incidence (26.83 and 31.47%) and severity (11.29 and 12.22%) were un significantly decreased when the two soil types were mixed (1:1). In addition, all recorded plant growth Parameters were significantly affected by both infection and the type of cultivated soil. Infection with different fungi reduced the all recorded plant parameters relative to non-inoculated transplants (control). All plant parameters tested were decreased to the minimal values when thyme grew in light textured soil. Mixing the two soil types with 1:1 ratio improved the plant vigor.
Thyme transplants immersed in Salicylic or Ascorbic acids (200 and 400 ppm) significantly reduced both incidence and severity of root rot/wilt of thyme under artificial inoculation with F. semetectum, R. solani or M. phaselicola under greenhouse condition comparing with control (untrated treatment). Salicylic acid gave the highest reduction on percentages of disease incidence and severity against both F. semetectum and R. solani, while Ascorbic acid gave the highest reduction on disease incidence and severity caused by M. phaseolina.
The treatment of thyme transplants with antioxidants significantly increased all vegetative parameters of artificially inoculated transplants with F. semetectum, R. solani or M. phaseolina under greenhouse conditions in comparing with control. The highest increases in plant parameters were recorded by Salicylic acid than Ascorbic acid. The best results for all plant parameters were obtained when transplants pretreated with Salicylic acid at 400 ppm when compared with control (untreated transplants).
Under the green house conditions, Cure–M72%, Rolex 50% or Rizolex-T 50%, applied as preplanting, using recommended or half recommended doses, caused significant reduction in the percentages of thyme root rot/wilt caused by F. semitectum, R.solani or M. phaseolina if compared with the control (inoculated and not treated plants). The percentages of disease incidence and severity significantly decreased with increasing the concentration of the tested compound. The fungicide Rizolex, however, preceded the other two tested compounds, in their efficiency.
The disease incidence was reduced by 30.11, 93.71 and 66.18%, also the disease severity was reduced by 50.2, 68.10 and 69.97% by applying Cure-M, Rolex and Rizolex, respectively at the 1st season. Results showed that Rizolex is considered the best compound was applied as transplants immersing to control thyme root rot/wilt under greenhouse condition. In the same time, plant parameters were improved when thyme transplants were treated with fungicides.
Under field conditions, thyme root rot/wilt incidence and severity were significantly reduced when SA or Rizolex-T were applied each alone or in combination compared with control at the two seasons of experiment. Application of SA and Rizolex- T together as transplants pretreating increased the reduction percent of DI and DS to the maximum; 95.24 and 97.01, respectively. The vegetable characters of thyme were significantly improved in all tested treatments comparing with control.. The combination between SA (200 ppm) and Rizolex (3 gL-1) was the most effective treatment in this respect.
Conclusion
Thyme root rot/ wilt have been shown in different districts in Minia governorate. The distribution of this disease increased year that may be due to cultivation annually in the same fields. Ascorbic and Salicylic acids and fungicides under studies proved to be inhibit the growth of fungi causing this disease under laboratory condition.