**Mycosynthesis of ZnO Nanoparticles Using** *Trichoderma* **spp. Isolated from Rhizosphere Soils and Its Synergistic Antibacterial E**ff**ect against** *Xanthomonas oryzae* **pv.** *oryzae*

**Balagangadharaswamy Shobha <sup>1</sup> , Thimappa Ramachandrappa Lakshmeesha 1,\*, Mohammad Azam Ansari <sup>2</sup> , Ahmad Almatroudi 3,\* , Mohammad A. Alzohairy <sup>3</sup> , Sumanth Basavaraju <sup>1</sup> , Ramesha Alurappa <sup>1</sup> , Siddapura Ramachandrappa Niranjana <sup>4</sup> and Srinivas Chowdappa 1,\***


Received: 28 July 2020; Accepted: 17 September 2020; Published: 20 September 2020

**Abstract:** The Plant Growth Promoting Fungi (PGPF) is used as a source of biofertilizers due to their production of secondary metabolites and beneficial effects on plants. The present work is focused on the co-cultivation of *Trichoderma* spp. (*T. harzianum* (PGT4), *T. reesei* (PGT5) and *T. reesei* (PGT13)) and the production of secondary metabolites from mono and co-culture and mycosynthesis of zinc oxide nanoparticles (ZnO NPs), which were characterized by a UV visible spectrophotometer, Powder X-ray Diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDAX) and Transmission Electron Microscope (TEM) and Selected Area (Electron) Diffraction (SAED) patterns. The fungal secondary metabolite crude was extracted from the mono and co-culture of *Trichoderma* spp. And were analyzed by GC-MS, which was further subjected for antibacterial activity against *Xanthomonas oryzae* pv. *Oryzae*, the causative organism for Bacterial Leaf Blight (BLB) in rice. Our results showed that the maximum zone of inhibition was recorded from the co-culture of *Trichoderma* spp. rather than mono cultures, which indicates that co-cultivation of beneficial fungi can stimulate the synthesis of novel secondary metabolites better than in monocultures. ZnO NPs were synthesized from fungal secondary metabolites of mono cultures of Trichoderma harzianum (PGT4), Trichoderma reesei (PGT5), Trichoderma reesei (PGT13) and co-culture (PGT4 + PGT5 + PGT13). These ZnO NPs were checked for antibacterial activity against Xoo, which was found to be of a dose-dependent manner. In summary, the biosynthesized ZnO NPs and secondary metabolites from co-culture of *Trichoderma* spp. are ecofriendly and can be used as an alternative for chemical fertilizers in agriculture.

**Keywords:** fungal nanotechnology; *Trichoderma* spp.; ZnO nanoparticles; antibacterial activity *Xanthomonas oryzae* pv. *oryzae*; co-cultivation; secondary metabolites
