Submitted to: American Society for Microbiology
Publication Type: Abstract only
Publication Acceptance Date: 5/20/2007
Publication Date: 5/20/2007
Citation: Wicklow, D.T., Poling, S.M., Summerbell, R. 2007. Occurrence of pyrrocidine production among acremonium zeae populations from maize grown in different regions [abstract]. American Society for Microbiology. Interpretive Summary:
Technical Abstract: Acremonium zeae is recognized as a protective endophyte of maize and a potential confounding variable in maize variety trials for resistance to pathogenic microbes and their mycotoxins. This fungus grows systemically in maize and produces pyrrocidines A and B, polyketide-amino acid-derived antibiotics exhibiting potent in-vitro activity against major stalk and ear rot pathogens of maize. An evaluation of a random sampling of A. zeae isolates accessioned by the ARS (NRRL) and CBS Culture Collections from 1969-1992 revealed that pyrrocidines were produced by 3/11 isolates from maize grown in regions with milder climates (e.g., Illinois, Nebraska, and Germany), and 10/12 isolates from maize grown in warmer regions (e.g., North Carolina, Georgia, Iran, and India). In regions where maize is more vulnerable to pathogen attack following the damaging effects of drought and temperature stress, selection may favor A. zeae endophytes that produce pyrrocidines as acquired chemical defenses. Cultures of A. zeae, representing 13 populations isolated from maize seeds harvested from different regions and years, were grown on PDA in Petri dishes. Excised portions of the developing colony and underlying agar (3g) were extracted with 7 ml acetonitrile. After filtering, 10 ul portions of the extracts were analyzed by LC-APCI-MS. Among 52 isolates representing four A. zeae populations from regions associated with drought and temperature stress (e.g., Arizona, California, and Texas), 49 isolates (94%) produced pyrrocidine A in amounts ranging from 1 to 248 ng (29 ave.)/10ul acetonitrile, and 51 isolates (98%) produced pyrrocidine B in amounts ranging from 2 to 440 ng (137 ave.). Among 102 isolates representing nine A. zeae populations from the Midwestern corn belt (e.g., Illinois, Indiana, Iowa, Kentucky, Michigan, and Nebraska), only one isolate produced pyrrocidine A (280 ng) and pyrrocidine B (411 ng). Pyrrocidines were produced by nearly all of the isolates representing A. zeae populations from warmer regions where maize is commonly subjected to drought and temperature stress, while only one pyrrocidine producing isolate was recorded among isolates representing A. zeae populations from the Midwestern corn belt. Clonal populations of A. zeae endophytes differing in their ability to produce pyrrocidines may be distributed with seed of maize cultivars grown in commercial plantings.