Technique for large scale isolation of Discula umbrinella and other foliar endophytic fungi from Quercus species

Abstract

This paper describes a useful large scale technique suitable for isolation of Discula umbrinella and other foliar endophytic fungi. This technique provides an efficient means to collect large numbers of fungal isolates necessary for fungal ecology and genetic variation studies. Also, this method is easily modified for isolation of other fungi residing within a leaf. An oversized vacuum filtration unit was built to accomodate large numbers of leaf discs and all sterilization procedures were carried out on this unit. Leaf discs were incubated on white oak leaf agar in 24-well tissue culture plates for a 12-hr light period at 24 C for Discula umbrinella conidiomata production. Conidia were streaked onto white oak leaf agar. Isolates were transferred to Difco potato dextrose agar and stored in sterile water at 24 C for future fungal population studies. Discula umbrinella infection levels on Quercus alba and Q. rubra were monitored monthly using this technique. Conidiomata infection levels within leaves of Q. alba were higher than Q. rubra in the months of May, Jun, and Jul. Leaves of Q. rubra showed higher infection levels in the months of Aug and Sept. The feasibility of isolating other endophytic fungi with the large scale technique was also tested. Using the large scale method, 18 different fungal isolates were collected from fallen leaves of Quercus alba. Tubakia dryina (Sacc.) Sutton was the most frequently isolated endophyte from fallen leaves regardless of the media used.

Key Words:

• endophytes
• oak anthracnose
• population genetics
• vacuum apparatus