Nitrogen metabolism of Leucostoma persoonii and L. cincta in virulent and hypovirulent isolates

Abstract

The nitrogen utilization pattern of two species of Leucostoma was examined using virulent isolates of L. persoonii and L. cincta, and two virus-infected hypovirulent isolates of L. persoonii. Virulent L. persoonii were able to utilize all of 47 nitrogen sources tested except anthranilic acid, cysteine, homocysteine, hydroxylamine, indole, lysine, urocanic acid, methylated purines and pyrimidines. Leucostoma cincta isolates were unable to use these latter compounds, acetamide and the branched side chain aliphatic amino acids: isoleucine, leucine, and valine. The ability to utilize branched aliphatic amino acids might be a species-specific characteristic. A virulent isolate of L. cincta, ATCC62910, also could not utilize nitrate and nitrite. The two hypovirulent L. persoonii isolates had a further restricted list of usable nitrogen sources. In addition to the nitrogen sources above, they were unable to grow on nitrate, nitrite and the branched aliphatic amino acids, as sole nitrogen sources. Growth of the two hypovirulent isolates on glutamic acid and aspartic acid, as well as aromatic amino acids was poor compared to virulent isolates. The patterns of inorganic nitrogen utilization were determined in reference to the known gene loci that control the process in fungi. Inability to utilize specific nitrogen sources is likely the result of mycovirus infection. Poor growth on several utilizable nitrogen sources might be influential in hypovirulence.

Key Words:

• Cytospora
• double-stranded RNA
• Leucocytospora
• mycovirus
• nutrition
• phenetic groups
• physiology
• selective medium
• Valsa
• virulence