# Exploring the Potential Applications of _Paecilomyces_ _Iilacinus_ 112
## 4 Discussion
variotti_ CDG33 to reduce the severity of diseases caused by different aerial and soil phytopathogens _Pythium aphanidermatum_ (81.5%), _Fusarium solani_ (72%), _Botrytis cinerea_ (51%), _Sclerotiuin sclerotorum_ (40%), and _Rhizoctonia solani_ (28%). By comparison, our _Paecilomyces__liacimus_ 112 was much more active against _Rhizoctonia solani_ (52.53% inhibition) and _Sclerotuin sclerotorum_ (50.23%), but less active against pathogens belonging to genres _Botrytis_ and _Fusarium_. Filamentous fungi produce a wide array of secondary metabolites; among them, siderophores play a significant role in promoting the growth of several plants by increasing Fe uptake in plants [45; 46; 47]. Siderophores are able to capture insoluble ferric ions (Fe\({}^{+3}\)) from different habitats and transport them into cell membranes through specific receptors. Given the importance of siderophore production, in our experimental study we evaluated the ability of _Paecilomyces__liacimus_ 112 to secrete these secondary metabolites. The qualitative test performed by culturing _Paecilomyces__liacimus_ 112 on 8-hydroxyquinoline-based medium presented a positive result, which is a good starting point for further application in the agriculture field. Similar studies showed the production of the siderophore by a _P. variotti_ isolate [35]. Furthermore, a _Paecilomyces variotti_ produces siderophores, mostly ferrirubin, a member of the class of ferric-iron (III) chelates [48; 49]. Phosphorus (P) is one of the most important minerals for plant growth. In most cases, phosphorus deficiency in the soil is alleviated by the addition of phosphate fertilizers; however, sometimes there are problems with the fixation of added P from chemical fertilizers. The soil-fixed P can be solubilized through the activity of microorganisms, namely fungi or bacteria, in connection with certain factors, such as the mechanism of solubilization, molecular genetics, and capacity to release P into the soil [50; 51]. Our results reveal that _Paecilomyces_ _illacinus_ 112 has the ability to solubilize P, the appearance of the transparent zone surrounding fungal colonies in a solid medium with Ca\({}_{3}\)(PO\({}_{4}\))\({}_{2}\) presenting a positive result. Other isolates belonging to the _Paecilomyces_ genus have been reported to function similarly. _Paecilomyces marquandii_ was described as an efficient phosphate solubilizer, especially grown in media with a wide range of carbon (fructose, galactose, glucose, glycerol, lactose, maltose, mannose, starch, and sucrose) and nitrogen sources (ammonium chloride, sulphate, nitrates, and urea) [52]. The complete growth and development of plants also depends on zinc, another essential micronutrient active in enzymatic reactions, carbohydrate metabolism, and the synthesis of proteins and auxins. Zinc existing in the soil is partially available since it is in insoluble form, and only cations Zn\({}^{+2}\) can be taken up by plants [53; 54]. In our tests, the _Paecilomyces_ _illacinus_ 112 isolate exhibited zones of solubilization in the in vitro qualitative tests carried out with three insoluble zinc sources (zinc oxide, zinc nitrate, and zinc carbonate). Another study also reported the use of a _Paecilomyces_ isolate as a potent bioinoculant for agricultural crops, an alternative to synthetic Zn sources [23]. The capability of _Paecilomyces_ _illacinus_ 112 to solubilize phosphorus and zinc is significant feature of plant growth-promoting agents. These properties could ameliorate the uptake of phosphate and zinc by the plants, resulting in increase in the vegetative and biological parameters. Endophytic fungi produce metabolic compounds important for their own biology and interactions with host plant. They secrete a wide range of hydrolytic extracellular enzymes that support their ecological role in combating pathogens through an important mechanism for fungal growth inhibition [55; 56; 57; 58].