The Effect of Some Fungicides and Genetic Resistance for Controlling Common Bunt in Group of T. aestivum Varieties Grown under Deir Ezzor Conditions

Yara Thalaj
General Commission for Scientific Agricultural Research-
Deir Ezzor Research Center
Alfurat University, Faculty of Agriculture
2009

Abstract

What is known to be very sensitive to several pests, among them common bunt it seriousness is owing to direct causes lead to destroying all the farmed grains in the spikes resulting in a big loss of the yield, may reach on single field to 80% or even 100% on others, and indirect causes related to affecting the quality of flour badly by some spores of this disease.
In spite of the great success achieved from controlling this disease using some fungicides all over the world, but it couldnt be eliminate completely. This is due to the high level of inoculums in soil, no treatment of grains with suitable fungicides or defects that may arise during grain treatment.
Objectives
1. Testing sensitivity of several Syrian durum wheat verities to the common bunt under the conditions of artificial infection of soil and grains with pathogens at depths of 3 and 6 cm.
2. Testing the efficacy of some fungicides with different chemical compositions and different mechanisms for controlling the disease, and determining their roles in raising the genetic tolerance under the previous conditions.
3.  Studying the effect of common bunt on grain yield of the different studied wheat varieties in various experimental treatments.
Materials and methods
1. Varieties:
Six cultivars of durum wheat, viz., Cham-4, Cham-6, Cham-8, Cham-10, Bohouth-4 and Bohouth-6 were selected. The cultivars are local and have different capacities in tolerance to common bunt disease and their date of approval for agricultural use.
2. Fungicides:
Five types of fungicides were selected to treat grains of wheat cultivars. They are as follows:
2.1 Vitfax (composed of carboxen 37.5% and thiram 37.5%) at the rate of 1kg /ton grains.
2.2 Agri spore (mancozeeb 60%) at the rate of 2 kg/ton grains.
2.3 Difedend (difenoconazol 3%) at the rate 1 liter/ton grains.
2.4 Amquite (difenoconazol1%) at rate of 1kg/ton grains.
2.5 Raxil (tebuconazol 2%) at rate of 2 kg/ton grains.
The study was carried out using two experiments per season, split plot design with 3 replications. Nine plots assigned to the six varieties used. The sub-plots were occupied by the five fungicides and sub-sub-plot used for the two depths of sowing (3 and 6 cm). In addition, control- 1 (uninfected but treated grains) and control- 2 (infected but untreated grains) for the first experiment, control- 1 (uninfected soil and untreated grains) for the second experiment. Number of the plots was 468 each of 1.5 x 4 m and has 5 rows at 30cm spacing.
Sowing, at the depth of 3 and 6 cm, was done using a metal ruler. Seed rate was 28kg/dunum or 250 grains 4 m per row. Sowing date was between 15-11 and 1-12 for both seasons.
Artificial infection of grains was done using spores the field fungi (at the rate of 19/100g grains and 5g/1kg soil) that cause common bunt disease of that collected from the study area where wheat varieties were attacked in the previous year.
Results
1. Triazolic fungicides had significantly reduced plant growth as compared to the traditional fungicides (vitfax and agrispore) and the infected and uninfected controls. This was shown through delaying germination of large numbers of wheat varieties grains studied and dealing seedling emergence by 3 – 5 days at the depth of 6cm. Average seedling lengths reduced by 20.7 – 29.5% and 7.4 – 18.2% under the conditions of artificial infection of grains and by 9.09 – 25.4% and 15.8 – 25.8% under the conditions of artificial infection of the soil at both depths of sowing respectively. Also, average root length was reduced to be 8.6 – 17.3% and 10.2-33.3% under the conditions of artificial infection of grains and 12.6 – 15% and 12.8 – 40% under the conditions of artificial infection of soil at the depth of sowing respectively. Average area of the coleoptiles was also reduced under the same conditions by 34.3 – 40% and 48.8-58.06% and by 31 – 43.1% and 50.8 – 55.6% respectively.
2. All studied cultivars of durum wheat showed high sensitivity to common bunt disease, where the percent of attacked spikes under the conditions of artificial infection of grains amounted to 31.2 – 51.6% and 33.6 – 61.3% in the first season, and between 43.6 – 57.6% and 44.5 – 62.6% in the second season for both depths of sowing respectively. But for the conditions of artificial infection of soil it varied between 30.5 – 49.2% and 33.4 – 57.2%, and between 42.7 – 56% and 43.3 – 62.7% for both seasons and the first and second of sowing depths respectively.
3. Triazolic fungicide significantly increased the genetic tolerance for the studied wheat varieties, protecting them from infection with common bunt attack during the experimental seasons. The efficiency of the fungicides varied between 40.9 – 59.3% at the sowing depth of 3 cm, and between 40.9 – 45%at the sowing depth of 6 cm under the conditions of artificial infection of grains, and between 41 – 71.5% and 41.9 – 48.3% under the conditions of artificial infection of soil at the first and second depths of sowing, respectively. Compared to vitafax, it varied compared to the control (infected but not treated under the condition of artificial infection of grains) between 89-91.4% and 89.6-98.05% and between 83.3-90.7% and 81.7-82.1% under the conditions of artificial infection of soil for the two depths respectively.
4. Treating the grains with triazolic fungicides led to an a significant increase in grain yield for the durum wheat varieties at 145.3 – 159% at the depth 3 cm and at 131.7 – 171.07% at the depth of 6 cm under the conditions of artificial infection of grains, and at 134.9-155.9% and 122.9 – 138.2% under the conditions of artificial infection of soil compared to the control (infected but untreated), and between 5.02-10.9% and 12.5-15.4% under the condition of artificial infections of grains, and between 19.6-27.5% and 27.07-44.8% under the conditions of artificial infection of soil compared to vitfax for the first and second depths respectively.