|FRENCH, ROY - Retired ARS Employee|
|PEDERSEN, JEFFREY - Retired ARS Employee|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2017
Publication Date: 10/18/2017
Publication URL: http://handle.nal.usda.gov/10113/5835520
Citation: Funnell-Harris, D.L., Scully, E.D., Sattler, S.E., French, R.C., ONeill, P.M., Pedersen, J.F. 2017. Differences in fusarium species in brown midrib sorghum and in air populations in production fields. Phytopathology. 107(11):1353-1363. https://doi.org/10.1094/PHYTO-08-16-3016-R.
Interpretive Summary: Several fungi can cause sorghum grain mold, which reduces grain quality in the field and during storage. Fungi in the Fusarium group were isolated from air and from brown midrib (bmr; plants with reduced lignin) and normal plants from two field locations in Nebraska, one irrigated and the other dryland. Analysis of DNA sequences from these fungi identified a common sorghum pathogen from the plants but this fungus was only found at low levels in air. Alternatively, numerous Fusarium pathogens of wheat and corn were identified from air samples, but only a few of these fungi were found in sorghum plants and at low levels. Analysis of air samples during the growing season showed that Fusarium populations early during the growing season were different from populations during grain development and harvest. Fusarium populations found in grain from normal and bmr plants at the irrigated field were different. However, Fusarium populations found in bmr and normal grain grown at the dryland field were very similar. Taken together these results showed that bmr with reduced lignin affected Fusarium populations in plants, but environment (irrigated versus dryland) also had a strong influence on Fusarium populations. These results also indicated that high levels of pathogens of wheat and corn in the air do not contribute greatly to sorghum grain mold.
Technical Abstract: Several Fusarium spp. cause sorghum (Sorghum bicolor) grain mold, resulting in deterioration and mycotoxin production in the field and during storage. Fungal isolates from the air (2005 to 2006) and from leaves and grain from wild-type and brown midrib (bmr)-6 and bmr12 plants (2002 to 2003) were collected from two locations. Compared with the wild type, bmr plants have reduced lignin content, altered cell wall composition, and different levels of phenolic intermediates. Multilocus maximum-likelihood analysis identified two Fusarium thapsinum operational taxonomic units (OTU). One was identified at greater frequency in grain and leaves of bmr and wild-type plants but was infrequently detected in air. Nine F. graminearum OTU were identified: one was detected at low levels in grain and leaves while the rest were only detected in air. Wright’s F statistic (FST) indicated that Fusarium air populations differentiated between locations during crop anthesis but did not differ during vegetative growth, grain development, and maturity. FST also indicated that Fusarium populations from wild-type grain were differentiated from those in bmr6 or bmr12 grain at one location but, at the second location, populations from wild-type and bmr6 grain were more similar. Thus, impairing monolignol biosynthesis substantially effected Fusarium populations but environment had a strong influence.