پديد آورندگان :
قدم خير، مريم دانشگاه رازي - گروه گياه پزشكي , عباسي، سعيد دانشگاه رازي - گروه گياه پزشكي , شريفي، روح الله دانشگاه رازي - گروه گياه پزشكي , فاطمي، اكرم دانشگاه رازي - گروه علوم و مهندسي خاك
كليدواژه :
پاخوره غلات , تغذيه خاك , تيو باسيلوس , گوگرد
چكيده فارسي :
بيماري پاخوره با عامل Gaeumannomyces tritici، يكي از مخرب‌ترين بيماري‌هاي ريشۀ گندم در سراسر جهان است. از اين رو ارائه راهكاري مديريتي جهت كنترل اين بيماري، بسيار ضروري به نظر مي‌رسد. هدف از اين پژوهش بررسي نقش تغذيه با گوگرد و اثر باكتري تيوباسيلوس بر وقوع بيماري پاخوره گندم بود. بدين منظور، ابتدا خصوصيات فيزيكي-شيميايي خاك مورد آزمون ارزيابي شد. گوگرد در غلظت‌هاي صفر، دو، چهار و هشت گرم بر كيلوگرم با خاك مخلوط شد و به سه صورت مورد مصرف قرار گرفت. در يك تيمار، خاك غني‌شده با غلظت‌هاي مختلف گوگرد بلافاصله با بيمارگر مايه‌زني و مورد كشت گندم قرار گرفت، در تيمار دوم خاك غني‌شده با غلظت‌هاي مختلف گوگرد به مدت دو ماه در گلخانه نگه‌داري شد و سپس مايه‌زني و كشت شد. در تيمار سوم نيز خاك غني‌شده با غلظت‌هاي مختلف گوگرد با باكتري تيوباسيلوس تيمار شد و بلافاصله مايه‌زني و كشت انجام شد. تجزيۀ خاك مورد آزمايش نشان داد اين خاك آهكي بوده و pH آن 7/24 يعني نسبتاً قليايي است. ميزان دسترسي نيتروژن و عنصر روي آن مناسب بود، ولي غلظت عناصر آهن، مس و تا حدودي فسفر خاك كم بود. نتايج نشان داد كه غلظت‌هاي مختلف گوگرد به صورت كشت بلافاصله و نگه‌داري دو ماهه اثر معني‌داري در كاهش بيماري پاخوره نداشتند، اما در تيمار همزمان گوگرد و باكتري تيوباسيلوس در غلظت هشت گرم بر كيلوگرم خاك شدت بيماري حدود 45 درصد كاهش يافت. تيمار خاك با گوگرد در غلظت دو گرم بر كيلوگرم خاك با و بدون نگه‌داري دو ماهه وزن خشك گياه را به ترتيب 20 و 25 درصد افزايش داد ولي افزايش بيشتر غلظت اثري بر افزايش رشد گياه نداشت. در تيمار گوگرد و باكتري تيوباسيلوس با افزايش غلظت گوگرد، وزن خشك گياه 25 درصد افزايش داشت. در مجموع، تركيب گوگرد و باكتري تيوباسيلوس مي‌تواند به عنوان رهيافتي اميدبخش در مهار پاخوره و بهبود رشد گندم مدنظر قرار گيرد.
چكيده لاتين :
Introduction: Wheat take-all caused by Gaeumannomyces tritici fungus is one of the most destructive
diseases in the world. The disease is common in alkaline to natural, non-fertile and low-drainage soils. Thereby,
wheat take-all can be suppressed by reducing soil pH. In recent years, sulfate-containing fertilizers had been
substituted with new sulfur-free fertilizers which decrease soil content of sulfur and sulfur-oxidizing bacteria,
significantly. So, soil amendment with mineral sulfur or Thiobacillus spp. could be reconsidered to reduce soil
pH. However, soil amendment with mineral sulfur seems to be more effective when the rhizosphere is colonized
by sulfur-oxidizing bacteria. This study aimed was to investigate the effect of mineral sulfur and Thiobacillus sp.
on take-all disease and wheat growth.
Materials and Methods: Physicochemical properties of soil were analyzed based on standard methods.
Sulfur was mixed with soil in 0, 2, 4 and 8 g/kg of soil with three methods. In the first method, sulfur amended
soil was inoculated with the pathogen and sown immediately. In the second method, amended soil was incubated
for two months then inoculated and seeded with wheat. In the third method, sulfur amended soil was inoculated
with Thiobacillus sp. bacteria and sown immediately. G. tritici inoculum was prepared on oat seeds and was
placed in a layer under plant seeds. Disease severity was checked once plants seedling in control pots exhibited
the disease symptoms. The experiments were carried out in a completely randomized design with four replicates.
Analysis of variance was done by SAS 9.1.
Results and Discussion: Analysis of soil showed the examined soil was calcareous and moderately alkaline.
It has appropriate nitrogen and zinc content but slightly Fe, Cu and P are deficient. Results exhibited that sulfur
amended has no significant role on take-all disease neither with incubation nor without incubation. However,
mixed treatment with sulfur and Thiobacillus sp. decreased disease severity in concentration depended on
manner. The highest disease suppression achieved in 8 g /kg sulfur of soil which decreased disease severity up to
45%. Soil amendment with 2 g/kg sulfur of soil either incubated or not increased plant dry weight 20 and 25%,
respectively. However, a further increase in sulfur concentration showed no more increase in plant growth. In a
combination with sulfur and Thiobacillus sp., wheat aerial parts dry weight was increased paralleled with an
increase in sulfur concentration and reach to 25% higher than control in 8 g /kg sulfur of soil. Calcareous soils
are highly buffered and it is very difficult to change their pH. In our experiment, the Soil amendment with
mineral sulfur was unable to reduce pH as much as necessary for Take-all suppression. However, sulfur had
synergistic interaction with Thiobacillus sp.. Indeed, these bacteria can colonize the plant rhizosphere efficiently.
Thereby, they can reduce the pH of the rhizosphere zone instead of whole balk soil. In this situation, G. tritici
could not survive in an acidic condition of the rhizosphere. On the other hand, mineral sulfur improved plant
growth in all concentrations. It should be considered that sulfur could be uptake by the plant as a nutrient
element. However, sulfur-oxidizing bacteria will help the plant to uptake sulfur more efficiently. It should be
considered that Thiobacillus is compatible with other biocontrol bacteria such as Bacillus and Pseudomonas.
These bacteria are highly effective in Take-all disease but cannot survive well in calcareous soils. Co-inoculation
of these bacteria with Thiobacillus sp. in the presence of sulfur seems to be a promising approach in biological
control of Take-all disease.
Conclusion: Our results showed that a combination of sulfur with sulfur-oxidizing bacteria could be a
promising approach in the suppression of Take-all in wheat. In recent years, integrated disease management and
integrated crop management receive high attention in susceptible agriculture. In these strategies, agricultural
practices such as plant nutrition are considered as multifaceted practice. This means that soil amended with
specific fertilizer not only increases plant growth but it can increase or decrease specific plant disease. In the
case of sulfur, this element not only decreases Take-all disease but also improves the availability of other
nutrients such as Fe, Zn and Cu. Furthermore, it should be considered that soil amendment with a low amount of
sulfur is not effective to reduce soil pH in buffered calcareous soils and we need to add sulfur-oxidizing bacteria
to improve fertilizer efficiency. This combination is effective against Take-all disease.
