In our lab, other researchers have used the following method to disinfect the plant tissue surface with great results (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8129196/) :

"Plant material was gently washed with sterile distilled water repeatedly to remove soil and dust particles. For surface sterilization, plant roots and leaves were placed into sterile Erlenmeyer flasks containing ethanol 75% v/v for 60 s with shaking and then in sterile Erlenmeyer flasks containing sodium hypochlorite solution 3% w/v–1 (NaClO) for 10 min. The plant materials were then placed again in ethanol 75% v/v for 60 s. To remove any remaining NaClO, plant materials were rinsed 10 times with sterile distilled water (dH2O). The sterilization and transfer procedures were carried out in a type II laminar flow hood. About 100 μL of the last rinse (for each analyzed sample) was plated on Nutrient Agar (NA) medium and monitored for microbial growth to evaluated surface sterilization efficiency. Only successfully sterilized root material was used further. Approximately 500 mg of leaves and roots per each species were weighed and slashed to small parts for further processing using a sterile scalpel and further grounded into a slurry with an autoclaved pestle and mortar. The slurry was transferred into sterile petri dishes and 30 mL of autoclaved dH2O was added. The petri dishes were sealed and placed onto a rotary shaker (150 rpm) at 25°C for 2 h. After shaking, 100 μl of the material in triplicate were inoculated on NA plates and incubated at 28°C. Colony forming units (cfus) were chosen from each plate based on their color, texture and morphology. Pure bacterial colonies were grown in Nutrient Broth (NB) and cells stocks were stored in 50% v/v glycerol at −80°C”.

Although it is almost a given the microbes that were left were endophytes , when it comes to isolating endophytes this article may be very useful since it compares different media used for isolation: (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4476825).

In any case, I would propose using a 1/10 869 semi solid medium (you can find more details for it in the aforementioned article). Recently I’ve also devised a “sort-of” protocol for inoculating bacteria in that medium since that’s the one I also use in the lab. You can find that protocol attached below.

I hope that helps!