In vitro evaluation of salt-based antifungal compounds for sustainable control of Neoscytalidium dimidiatum

Abstract

Objective: This study evaluated the antifungal potential of various salts—specifically ammonium, borate, calcium, magnesium, potassium, and sodium compounds—against two isolates (Ol_Dr04 and Ciar 64) of Neoscytalidium dimidiatum under in vitro conditions. The goal was to assess the efficacy of these salts in inhibiting mycelial growth, arthrospore germination, and germ tube elongation under both fixed and adjusted pH conditions. Materials and Methods: In this study, the mycelial growth of N. dimidiatum isolates was first observed across a pH range of 2 to 12 to determine the optimal pH levels. Subsequently, the antifungal efficacy of 1% concentrations of ammonium, borate, calcium, magnesium, potassium, and sodium salts was assessed under both fixed and adjusted pH (5) conditions for both isolates. Effective salt concentrations (EC50) needed to achieve a 50% reduction in mycelial growth, arthrospore germination, and germ tube elongation were calculated using probit analysis. Additionally, minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values were determined for each salt under the tested conditions. Results: Under fixed pH conditions, 1% concentrations of ammonium (bicarbonate and carbonate), borate (anhydrous borax, Etidot-67, and hydrated borax), and sodium (benzoate, citrate tetrahydrate, and metabisulfite) salts completely inhibited mycelial growth in both fungal isolates. However, under adjusted pH (5) conditions, only sodium benzoate and metabisulfite maintained the same inhibitory effect. At adjusted pH, calcium oxide and propionate also fully suppressed mycelial growth. Sodium metabisulfite emerged as the most effective antifungal compound, with remarkably low EC50 values (0.016 and 0.017%; w/v), MIC (0.0625 and 0.0625%; w/v), and MFC (0.0625% and 0.0625%; w/v) concentrations. Furthermore, with EC50 below 0.03125%, sodium metabisulfite remained the strongest inhibitor in both arthrospore germination and germ tube elongation assays. Conclusion: These results highlight the potential of sodium metabisulfite, ammonium bicarbonate, and ammonium carbonate salts as environmentally friendly alternatives to conventional fungicides. Further in vivo studies are recommended to validate these findings and explore practical applications in sustainable plant disease management.

Keywords

• Neoscytalidium dimidiatum
• antifungal salts
• EC50
• MIC
• MFC
• mycelial growth
• arthrospore germination
• germ tube elongation

Neoscytalidium dimidiatum’un sürdürülebilir kontrolünde tuz bazlı antifungal bileşiklerin in vitro değerlendirilmesi

Öz

Amaç: Bu çalışmada, amonyum, borat, kalsiyum, magnezyum, potasyum ve sodyum bileşiklerini içeren çeşitli tuz gruplarının, Neoscytalidium dimidiatum’un iki izolatı (Ol_Dr04 ve Ciar 64) üzerindeki antifungal potansiyeli in vitro koşullarda değerlendirilmiştir. Farklı tuzların sabit ve ayarlanmış pH koşullarında miselyal gelişimi, arthrospor çimlenmesi ve çim tüpü uzamasını engelleyici etkileri analiz edilmiştir. Materyal ve Yöntem: Çalışmada, öncelikle N. dimidiatum izolatlarının pH 2-12 aralığında miselyal gelişimi gözlemlenmiş ve optimum pH seviyeleri belirlenmiştir. Ardından, her iki izolat üzerinde amonyum, borat, kalsiyum, magnezyum, potasyum ve sodyum tuzlarının %1’lik konsantrasyonlarının sabit ve ayarlanmış pH (5) koşullarındaki antifungal etkinliği değerlendirilmiştir. Misel gelişiminde, arthrospor çimlenmesinde ve çim tüpü uzamasında %50 azalma sağlamak için gereken etkili tuz konsantrasyonları (EC50) probit analizi kullanılarak hesaplanmıştır. Ayrıca, minimum inhibisyon konsantrasyonu (MIC) ve minimum fungisidal konsantrasyon (MFC) değerleri de tespit edilmiştir. Araştırma Bulguları: Sabit pH koşullarında, amonyum (bikarbonat ve karbonat), borat (susuz boraks, Etidot-67 ve sulu boraks) ve sodyum (benzoat, sitrat tetrahidrat ve metabisülfit) tuzlarının %1’lik konsantrasyonları, her iki fungus izolatının miselyal gelişimini tamamen engellemiştir. Ancak, ayarlanmış pH (5) koşullarında, bu etkili tuzlardan yalnızca sodyum benzoat ve sodyum metabisülfit aynı engelleyici etkiyi göstermiştir. Ayarlanmış pH koşullarında ayrıca kalsiyum oksit ve kalsiyum propiyonat da miselyal gelişimi tamamen durdurmuştur. Sodyum metabisülfit, son derece düşük EC50 (%0.016 ve 0.017; w/v), MIC (%0.0625 ve 0.0625; w/v) ve MFC (%0.0625 ve %0.0625; w/v) değerleri ile en etkili antifungal bileşik olarak öne çıkmıştır. Ayrıca, %0.03125’in altındaki EC50 değeriyle sodyum metabisülfit, arthrospor çimlenmesi ve çim tüpü uzama testlerinde de en güçlü inhibitör olmuştur. Sonuç: Bu sonuçlar, sodyum metabisülfit, amonyum bikarbonat ve amonyum karbonat tuzlarının geleneksel fungisitlere çevre dostu alternatif olarak potansiyelini ortaya koymaktadır. Bu bulguları doğrulamak ve bitki hastalıklarının sürdürülebilir mücadelesinde pratik uygulamaların araştırılması için daha fazla in vivo çalışma yapılması önerilmektedir.

Anahtar Kelimeler

• Neoscytalidium dimidiatum
• antifungal tuzlar
• EC50
• MIC
• MFC
• miselyal gelişim
• arthrospor çimlenmesi
• çim tüpü gelişimi

Kaynakça

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