Basil Leaf–Based Agar Medium for the Isolation of Fungal Endophytes from Sweet Basil

Fungal endophytes are important components of plant-associated fungal communities and have considerable potential for agricultural and biotechnological applications. This study evaluated basil leaf agar (BLA), formulated using dried basil leaves as a nutrient source, as an alternative culture medium for the isolation of endophytic fungi from Ocimum basilicum. Endophytic fungi were isolated using BLA and potato dextrose agar (PDA) and identified based on morphological characteristics and internal transcribed spacer (ITS) rDNA sequence analysis. Eight fungal species, Alternaria alternata NZ01, Cladosporium halotolerans NZ02, Curvularia lunata NZ03, Diaporthe stewartii NZ04, Epicoccum sorghinum NZ05, Penicillium chrysogenum NZ06, Phyllosticta capitalensis NZ07, and Quambalaria cyanescens NZ08, were identified on BLA, whereas six species were recovered on PDA from the same tissue, with D. stewartii NZ04 and P. capitalensis NZ07 not detected on PDA. The two species D. stewartii NZ04, and P. capitalensis NZ07 that were exclusively detected on BLA were selected for further evaluation. These isolates showed higher radial growth on modified supplemented PDA (MSPDA) than on standard PDA, indicating that optimization of Mn and P availability and reduction of Na content improved the growth-supporting capacity of PDA. Overall, BLA demonstrated potential as a low-cost, natural, basil-based medium for the selective isolation and cultivation of endophytic fungi associated with O. basilicum, while MSPDA provided an improved medium for subsequent cultivation of selected basil endophytic fungi.