*3.5. In Vitro Screening of PGP Strains of Trichoderma spp. for Its Antibacterial Activity by Agar Plug Method against Xanthomonas oryzae pv. oryzae (Xoo)*

The control of a broad range of plant pathogens, including fungal, bacterial and viral diseases, through elicitation of Induced Systemic Resistance (ISR) by *Trichoderma* spp. or localized resistance has been reported. Some *Trichoderma* spp. rhizosphere-competent strains have been shown to have direct effects on plants, increasing their growth potential and nutrient uptake, fertilizer use efficiency, percentage and rate of seed germination and stimulation of plant defenses against biotic and abiotic damage by Hermosa et al. [49]. A total of 35 *Trichoderma* spp. were subjected for preliminary antibacterial activity screening on solid media. The plates were pre swabbed with Xoo and the agar plugs of 7 mm of fungi taken from an actively growing region of 7-day-old culture were placed on the Mueller Hinton agar (MHA). The plates were kept for incubation in the incubator for 24 h at 28 ◦C. After the incubation period, the plates were observed for zone of inhibition and in each plate, a standard tetracycline was used as a positive control and distilled water was taken as a negative control. All the isolates showed activity against the tested three plant pathogenic bacteria Xoo. The majority of these isolates showed a wide range of inhibition of the Xoo cultures. The zone of inhibition ranged from 11 mm to 25 mm. There are reports of *Trichoderma harzianum* isolate which showed strong antagonism against fungal species by Leelavathi et al. [50] (Figure S1) (Table 1). Based on the zone of inhibition, three *Trichoderma* spp. were selected for further analysis.
