Occurrence of pyrrocidine and dihydroresorcylide production among<i>Acremonium zeae</i>populations from maize grown in different regions
Bibliographic record
Abstract
Acremonium zeae is recognized as a protective endophyte of maize (Zea mays). Thus, it is 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 number of A. zeae isolates accessioned by the USDA Agricultural Research Service Culture Collection (NRRL) and CBS Culture Collections from 1969 to 1992 revealed that pyrrocidines were produced by 5 of 11 isolates from maize grown in regions sharing a milder temperate climate with cold winters (e.g., Illinois, Nebraska, and Germany) and by 10 of 12 isolates from maize grown in warmer regions (e.g., North Carolina and Georgia, USA; Iran; and India). Cultures of A. zeae representing 13 populations isolated from maize seeds harvested from different regions and years were grown on potato dextrose agar in Petri dishes. Excised portions of the developing colony and underlying agar were extracted and analyzed by liquid chromatography – atmospheric pressure chemical ionization interface – mass spectrometry. 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 (mean 29 ng), and 51 isolates (98%) produced pyrrocidine B in amounts ranging from 2 to 440 ng (mean 137 ng). In contrast, 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). During the population study, a new secondary metabolite of A. zeae, dihydroresorcylide, was discovered, and its distribution among the population is described. 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. Key words: Acremonium zeae, blackened bundles, cerebroside, dihydroresorcylide, disease suppression, endophyte, maize, polyketide antibiotics, pyrrocidines, stress damage, seedborne. Acremonium zeae est reconnu en tant que champignon endophyte protecteur du maïs. Il s’agit par conséquent d’un facteur confusionnel potentiel dans les essais de variété effectués sur le maïs afin d’en évaluer la résistance aux microbes pathogènes et à leurs mycotoxines. A. zeae pousse systématiquement sur le maïs et produit des pyrrocidines A et B, c’est-à-dire des antibiotiques polykétides dérivés d’acides aminés qui affichent une forte activité in vitro contre les principaux agents pathogènes causant la fusariose de l’épi et la pourriture des tiges chez le maïs. Une évaluation d’un nombre d’isolats d’ A. zeae, répertoriés, de 1969 à 1992, par l’Agricultural Research Service Culture Collection NRRL et le CBS Culture Collection a démontré que 5 des 11 isolats obtenus de plants de maïs cultivés dans des régions qui connaissent des étés doux et des hivers froids (p. ex., Illinois, Nebraska, Allemagne) produisaient des pyrrocidines, de même que 10 des 12 isolats cultivés dans des régions plus chaudes (p. ex., Caroline du Nord et Géorgie, États-Unis; Iran; Inde). Afin de les faire croître, des cultures d’ A. zeae, représentant 13 populations isolées à partir de semences de maïs récoltées dans diverses régions et au cours d’années différentes, ont été placées dans des boîtes de Pétri sur de la gélose dextrosée à la pomme de terre. Des portions isolées de colonies et de gélose sous-jacente ont été extraites et analysées par LC-APCI-MS. Parmi les 52 isolats représentant 4 populations d’ A. zeae provenant de régions associées aux stress causés par la sécheresse et la température (p. ex., Arizona, Californie, Texas), 49 isolats (94 %) ont produit de la pyrrocidine A en quantité variant de 1 à 248 ng (moyenne de 29 ng) et 51 isolats (98 %) ont produit de la pyrrocidine B dont les quantités variaient de 2 à 440 ng (moyenne de 137 ng). Par ailleurs, parmi les 102 isolats représentant 9 populations d’ A. zeae issues de la ceinture de maïs des États du Midwest (p. ex., Illinois, Indiana, Iowa, Kentucky, Michigan, Nebraska), un seul isolat a produit de la pyrrocidine A (280 ng) et de la pyrrocidine B (411 ng). Au cours de l’étude de populations, un nouveau métabolite secondaire d’ A. zeae, le dihydroresorcylide, a été découvert et l’on décrit sa distribution dans la population. Des semences de cultivars de maïs cultivées commercialement peuvent contenir des populations clonales d’endophytes d’ A. zeae dont la capacité à produire des pyrrocidines est variable. Mots-clés : Acremonium zeae, maladie des faisceaux noirs, cérébroside, dihydroresorcylide, suppression des maladies, endophyte, antibiotiques polykétides, pyrrocidines, dommages dus au stress, transmis par semence.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".