A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: January 11, 2008
Source: Plant Disease 91(10), 1365 (October 2007) [edited] <http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-91-10-1365A>
Leaf blight and vascular wilt in maize and sorghum in Mexico
_Zea mays_ and _Sorghum bicolor_ are important crops for animal
and human nutrition worldwide. In the Central Highland Valley of
Mexico, both crops are extremely important, and research is
aimed toward increasing yield, disease resistance, and crop
adaptation from 1900m
[6233 feet] to 2700m [8858 feet] elevation. In a 3-year field
breeding experiment (2004 to 2006), leaf blight and vascular
wilt symptoms were frequently observed in contiguous plots of
maize and sorghum crops in Montecillo, Mexico, and maize plots
in Tecamac, Mexico.
To identify and characterize the causal agent of these symptoms,
isolations were conducted on leaves from areas where healthy and
diseased tissues converged. A total of 12 isolates were selected
for further characterization. Physiological and biochemical
tests revealed characteristics of _Pantoea agglomerans_. Further
identification of these isolates was accomplished by DNA
analysis. In this analysis, a total of 5 of the 16S rRNA gene
sequences were obtained by Polymerase Chain Reaction (PCR) and
were grouped into the _P. agglomerans_ genetic cluster. There
was a 98 to 99 percent similarity of these sequences with _P.
agglomerans_ strain ATCC 27155.
Pathogenicity of the 12 isolates was confirmed by injecting
inoculum into stems of 3-week-old maize and sorghum seedlings in
the greenhouse.
Also, seedlings were inoculated with water, nonpathogenic
isolates of _P. agglomerans_ from maize, and not inoculated as
negative controls.
All test strains developed water-soaked lesions on juvenile
leaves at 8 days post-inoculation and were followed by chlorotic
to straw-colored leaf streaks and then leaf blight symptoms at 3
weeks post-inoculation.
All negative control seedlings did not develop symptoms. In
addition, the 12 isolates were infiltrated into tobacco leaves
that displayed a hypersensitive response at 4 days. Isolates
were reisolated, and the 16S rRNA gene fragments were 100
percent similar to their original isolate sequences.
_P. agglomerans_ has been reported to affect other crops,
including chinese taro in Brazil (2007), onion in the United
States (2006) and South Africa (1981), and pearl millet in
Zimbabwe (1997); however, to our knowledge, this is the 1st
report of _P. agglomerans_ associated with leaf blight and
vascular wilt symptoms in maize and sorghum in the Central
Highland Valley of Mexico.
[Byline: G. Morales-Valenzuela et al.]
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[The genus _Pantoea_ belongs to the family of
_Enterobacteriaceae_ which also comprises genera pathogenic to
humans or animals. However, the majority of its members are
plant-associated. Species in the genus cause a variety of
diseases and can affect a number of crops. For example, _P.
stewartii_ causes Stewart's bacterial wilt on maize, an
important insect-borne disease in parts of the USA and Europe; a
new disease on maize, brown stalk rot, was recently reported to
be caused by _P.
ananatis_ and an undescribed novel _Pantoea_ species; _P.
citrea_ is the causal agent of pink disease of pineapple; center
rot of onion is caused by _P. ananatis_; a bacterial blight of
_Eucalyptus_ and a leaf blotch disease of sudangrass have also
been associated with _Pantoea_ species.
_P. agglomerans_ is widely distributed and the effect of
different strains on host plants can vary dramatically. There
are strains which cause plant diseases like the ones mentioned
in the above report; non-pathogenic strains which live as common
epiphytes of many plant species; strains which are reported to
promote plant growth and have a beneficial effect on yield for
some cereals; and strains which are being suggested as a
biocontrol agent for fireblight of pome fruit, a serious disease
caused by the bacterium _Erwinia amylovora_. Occasionally, the
bacterium has also been reported from human tissues after
plant-related injuries.
Maps
Mexico:
<http://www.mexico.us/map.htm>
and
<http://healthmap.org/promed?v=24,-102.5,5>
Mexico State:
<http://www.travelamap.com/mexico/estadmexico.htm>
Pictures
_P. agglomerans_ symptoms on chinese taro (_Alocasia cucullata_)
leaf:
<http://www.bspp.org.uk/NDR/jan2007/2006-99-1a.jpg>
Symptoms of Stewart's wilt on maize:
<http://www.invasive.org/images/768x512/0454008.jpg>
Pink disease of pineapple:
<http://www.apsnet.org/online/feature/pineapple/image/pink1sm.jpg>
Links
_P. agglomerans_ on pearl millet:
<http://www.ars.usda.gov/Research/docs.htm?docid=8896#Unnamed%20Bacterial%20Disease>
_P. agglomerans_ on onions:
<http://www.apsnet.org/pd/searchnotes/2006/PD-90-1551A.asp>
_P. agglomerans_ for biocontrol of fireblight:
<http://epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_006511.htm>
and
<http://www.pmra-arla.gc.ca/english/pdf/reg/reg2006-13-e.pdf>
Growth promoting effect of _P. agglomerans_ on cereal species:
<http://www.springerlink.com/content/y2ukn5467x7137j0/>
and
<http://www.philip-jacobs.de/endophyt/pantset.htm>
(in German)
Association with human tissues:
<http://jcm.asm.org/cgi/content/full/45/6/1989>
and <http://adc.bmj.com/cgi/content/full/88/6/542>
(subscription) Brown stalk rot of maize:
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-91-6-0711>
Stewart's bacterial wilt of maize:
<http://www.ca.uky.edu/agc/pubs/ppa/ppa33/ppa33.htm>
and
<http://nu-distance.unl.edu/Homer/disease/agron/corn/CoStewWlt.html>
Pink disease of pineapple:
<http://www.apsnet.org/online/feature/pineapple>
_Pantoea_ taxonomy:
<http://www.bacterio.cict.fr/p/pantoea.html>
Information on fireblight:
<http://www.eppo.org/QUARANTINE/bacteria/Erwinia_amylovora/ERWIAM_ds.pdf>
and
<http://www.fireblight.com/>
- Mod.DHA]
[see also in
the
archive:
2007
----
Brown stalk rot, maize - South Africa: 1st report 20070620.1993]
