Nutritional Factors Affecting Synnema and Dark Pigment Formation by Ceratocystis Ulmi

ABSTRACT

Modifying the nutritional constituents of a defined agar medium containing low levels of glucose, asparagine, and linoleic acid affected formation of synnemata and dark mycelial pigment by Ceratocystis ulmi. Except for a darkly pigmented variant, no pigment or synnemata were formed on the glucose and asparagine medium without linoleic acid. With the addition of linoleic acid, or the substitution of glucose with potassium acetate and/or asparagine with tyrosine, the medium was suitable for both dark pigment and synnemata formation by some C. ulmi isolates. Media without linoleic acid also supported pigment and synnema formation by some isolates when acetate and/or tyrosine were used as the carbon or nitrogen sources, respectively. Generally, C. ulmi isolates known to be more aggressive produced more synnemata and dark pigment on the media containing glucose and linoleic acid than did those isolates known to be less aggressive.

Key Words:

• Ceratocystis ulmi
• synnemata
• pigment
• acetate