Microencapsulation of seed-coating tebuconazole and its effects on physiology and biochemistry of maize seedlings

Tebuconazole is a triazole systemic fungicide that is commonly used to treat fungal pathogens of crops, but at high doses can reduce seed germination. Seeds with microcapsulated tebuconazole were investigated to determine effects of this method on maize seedlings and the bioefficacy against maize head smut (Sphacelotheca reiliana). The ethyl cellulose (EC)-based microcapsules had encapsulation efficiency of 90.6%, and average size of 1.6 μm. A release kinetic study revealed that tebuconazole release from EC-based microcapsules fits the model (Mt/Mz=kt(n)+C). Glasshouse studies indicated that maize seedling emergence and growth were negatively affected in an exponential manner as predicted by model Y=A+B×e((-x/k)). However, microencapsulation could induce tebuconazole's growth promoting effects by increasing emergence, shoot fresh weight, root fresh weight, carotenoid and chlorophyll content. Phytohormone analysis indicated the beneficial effects of microencapsulated tebuconazole were due to the sustained release of tebuconazole that appeared to influence the balance of phytohormones in maize seedlings. Contrary to conventional tebuconazole, microencapsulated seed-coated tebuconazole can lead to slightly increased gibberellins (GA) level and disappearance of abscisic acid (ABA) accumulation in maize. In addition, microcapsule formulation of tebuconazole was found to provide better protection against maize head smut when compared to conventional formulation.