2.3. Antifungal activity of essential oils on mycelial growth in vitro conditions
The antifungal tests of essential oils were carried out for assessing its contact and volatile phase effects towards mycelial growth of B. cinerea as described previously (Soylu et al., 2006). For determi- nation of contact effects, the essential oils were dispersed as an emulsion in water using ethanol and Tween 20 (0.1% v/v) and added to PDA immediately before it was emptied into the glass Petri dishes (90 × 20 mm in diameter) at a temperature of 40–45 °C. The concentrations tested were 0.4 to 25.6 μg/ml. The controls received the same quantity of ethanol and Tween 20 mixed with PDA. B. cinerea was inoculated immediately by plating in the centre of each plate with a 7 mm diameter disc of the fungus, cut with a sterile cork borer from the edge of actively growing cultures on PDA plates. The Petri dishes were incubated in the dark at 22 °C. For determination of volatile phase effects, glass Petri dishes (90 × 20 mm, which offer 80 ml air spaces after addition of 20 ml agar media) were used. The Petri dishes inoculated as described above at different concentrations of essential oils were added to sterile filter papers (10 mm diameter, Whatman no.1) and placed on the inner surface of the lid of Petri dishes to obtain final concentrations of 0.05 to 1.6 μm/ml air. The Petri dishes were sealed immediately with parafilm to prevent loss of essential oil vapours and incubated at 22 °C. The mean radial mycelial growth of the pathogen was determined by measuring the diameter of the colony in two directions at right angels when the plate surface of the control Petri was covered by fungus 7 days after inoculation. The fungistatic–fungicidal nature of essential oils was tested by observing revival of growth of the inhibited mycelial disc following its transfer to non-treated PDA. A fungicidal effect was where there was no growth, whereas a fungistatic effect was where temporary inhibition of microbial growth occurred. The agar discs of B. cinerea, which failed to grow were either transferred onto agar media without oils (for contact phase effect of oils) or onto lids of the plate containing ethanol and Tween 20 (0.1% v/v) without oil (for volatile phase effect of oils). Petri plates were incubated for 5days. Activity of the each concentration of the various oils was considered fungicidal if the pathogen did not grow or fungistatic if the pathogen growth occurred.
For each concentration, five replicate plates were used. The mean growth values were obtained and then converted in to the inhibition percentage of mycelial growth in relation to the control treatment by using the formula, MGI(%) = ((dc − dt) / dc) × 100, dc and dt represent mycelial growth diameter in control and treated Petri plates, respectively. The experiments were conducted twice.
2.4. Effect of essential oil on conidial germination and germ tube elongation
The effects of essential oil upon the spore germination and germ tube elongation of B. cinerea were described in our earlier study (Soylu et al., 2005). Spore suspension (104 spores ml−1) of B. cinerea was prepared from actively growing culture (7–8 days old) in distilled sterile water. Three different 50 μl aliquots of the spore suspension drops were spread onto the surface of PDA medium supplemented with different concentrations of essential oil in contact or volatile phases as described before. Sterile distilled water, containing 0.01% Tween 20, was used in place of the essential oils as control. Plates were incubated at 22 °C until the germination in the control reached N 80% (10–12 h according to the rate of germination of the fungus) Afterward, spore germination was stopped by applying a drop of lactophenol-cotton blue to the inoculation sites on plates. Germination was defined as the point at which the germ tube length exceeded the spore diameter. The percentage of spore germination and the lengths of germ tubes (three replicates were conducted for each treatment, and a minimum of 100 spores were counted in each replicate) were estimated under a microscope (Olympus BX51, Tokyo, Japan), using a micrometer. The percent inhibition was calculated according to Abbott's formula: MGI(%)=
2.3 การกิจกรรมต้านเชื้อราของน้ำมันบน mycelial การเจริญเติบโตในหลอดThe antifungal tests of essential oils were carried out for assessing its contact and volatile phase effects towards mycelial growth of B. cinerea as described previously (Soylu et al., 2006). For determi- nation of contact effects, the essential oils were dispersed as an emulsion in water using ethanol and Tween 20 (0.1% v/v) and added to PDA immediately before it was emptied into the glass Petri dishes (90 × 20 mm in diameter) at a temperature of 40–45 °C. The concentrations tested were 0.4 to 25.6 μg/ml. The controls received the same quantity of ethanol and Tween 20 mixed with PDA. B. cinerea was inoculated immediately by plating in the centre of each plate with a 7 mm diameter disc of the fungus, cut with a sterile cork borer from the edge of actively growing cultures on PDA plates. The Petri dishes were incubated in the dark at 22 °C. For determination of volatile phase effects, glass Petri dishes (90 × 20 mm, which offer 80 ml air spaces after addition of 20 ml agar media) were used. The Petri dishes inoculated as described above at different concentrations of essential oils were added to sterile filter papers (10 mm diameter, Whatman no.1) and placed on the inner surface of the lid of Petri dishes to obtain final concentrations of 0.05 to 1.6 μm/ml air. The Petri dishes were sealed immediately with parafilm to prevent loss of essential oil vapours and incubated at 22 °C. The mean radial mycelial growth of the pathogen was determined by measuring the diameter of the colony in two directions at right angels when the plate surface of the control Petri was covered by fungus 7 days after inoculation. The fungistatic–fungicidal nature of essential oils was tested by observing revival of growth of the inhibited mycelial disc following its transfer to non-treated PDA. A fungicidal effect was where there was no growth, whereas a fungistatic effect was where temporary inhibition of microbial growth occurred. The agar discs of B. cinerea, which failed to grow were either transferred onto agar media without oils (for contact phase effect of oils) or onto lids of the plate containing ethanol and Tween 20 (0.1% v/v) without oil (for volatile phase effect of oils). Petri plates were incubated for 5days. Activity of the each concentration of the various oils was considered fungicidal if the pathogen did not grow or fungistatic if the pathogen growth occurred.สำหรับแต่ละความเข้มข้น มีใช้แผ่น 5 replicate ค่าเฉลี่ยการเจริญเติบโตได้ และจากนั้น แปลงเป็นในเปอร์เซ็นต์ยับยั้งการเจริญเติบโต mycelial เกี่ยวกับการรักษาควบคุม โดยใช้สูตร MGI(%) = ((dc − dt) / dc) × 100, dc และ dt หมายถึงเส้นผ่าศูนย์กลางเจริญเติบโตของ mycelial ในการควบคุมและบำบัด Petri แผ่น ตามลำดับ ได้ดำเนินการทดลองสอง2.4. ผลของน้ำมันหอมระเหย conidial การงอกและ elongation จมูกหลอดผลของน้ำมันหอมระเหยตามการงอกสปอร์และจมูกหลอด elongation ของ cinerea เกิดได้อธิบายไว้ในการศึกษาก่อนหน้านี้ของเรา (Soylu et al., 2005) ระงับสปอร์ (104 เพาะเฟิร์น ml−1) การเกิด cinerea ถูกเตรียมจากวัฒนธรรม (อายุ 7-8 วัน) ในน้ำกลั่นฆ่าเชื้อการเจริญเติบโตอย่างแข็งขัน สามแตกต่างกัน 50 μl aliquots หยดระงับสปอร์ได้แพร่กระจายไปบนพื้นผิวของ PDA สื่อเสริม ด้วยความเข้มข้นแตกต่างกันของน้ำมันหอมระเหยในระยะติดต่อ หรือระเหยตามที่อธิบายไว้ก่อน กอซกลั่นน้ำ ประกอบด้วย 0.01% Tween 20 ไม่ใช้น้ำมันหอมระเหยเป็นตัวควบคุม แผ่นก็ incubated ที่ 22 ° C จนถึงการงอกในตัวควบคุม N 80% (h 10-12 ตามอัตราการงอกของเห็ดรา) หลัง หยุดการงอกของสปอร์ โดยใช้หยดสีฟ้าผ้าฝ้าย lactophenol ไซต์ inoculation บนแผ่น การงอกได้กำหนดเป็นจุดที่ความยาวท่อจมูกเกินเส้นผ่าศูนย์กลางสปอร์ เปอร์เซ็นต์การงอกของสปอร์และความยาวของจมูกหลอด (เหมือนกับสามได้ดำเนินการสำหรับแต่ละการบำบัด และอย่างน้อย 100 เพาะเฟิร์นนับได้ในแต่ละซ้ำ) ได้ประเมินภายใต้กล้องจุลทรรศน์ (Olympus BX51 โตเกียว ญี่ปุ่น), ใช้เป็นไมโครมิเตอร์ เปอร์เซ็นต์การยับยั้งการเปลี่ยนคำนวณตามสูตรของ Abbott: MGI(%) =
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