Chemistry: molecular biology and microbiology – Micro-organism – per se ; compositions thereof; proces of... – Bacteria or actinomycetales; media therefor
Reexamination Certificate
1999-10-07
2001-11-06
Marx, Irene (Department: 1651)
Chemistry: molecular biology and microbiology
Micro-organism, per se ; compositions thereof; proces of...
Bacteria or actinomycetales; media therefor
C424S093460, C504S117000
Reexamination Certificate
active
06312940
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Head scab, also known as Fusarium head blight (FHB), is a devastating disease of wheat and barley that is primarily caused by the fungus
Gibberella zeae
(anamorph=
Fusarium graminearum
). This disease can reach epidemic levels and causes extensive damage to wheat and barley in humid and semi-humid wheat growing areas of the world. In recent growing seasons, the disease has caused large scale devastation in the United States, Canada and China. FHB was responsible for almost 500 million bushels of wheat lost in the United States from 1991 until present. Economic loss has been estimated at between 1.3 to 2.6 billion during this time period. In an epidemic in Indiana in 1986, grain samples from 43 of 44 counties had scab [Tuite et al., (1990)
Plant Dis
. 74:959-962]. Other countries of the world that produce large amounts of wheat in humid and semi-humid regions and would be susceptible to major outbreaks of FHB include India, Russia, France, Germany and the United Kingdom.
The infection of seed by
G. zeae
reduces seed germination, seedling vigor and plant emergence [Bechtel et al., (1985)
Cereal Chem
. 62:191-197]. Infection of wheat kernels by
G. zeae
reduces grain yield and affects grain quality [Clear et al., (1990)
Can. J. Plant Sci
. 70:1057-1069]. Reductions in grain yield are at least partially attributable to the pathogen producing the vomitoxin deoxynivalenol (DON) [Snijders, (1990)
Neth J. Plant Pathol
. 96:187-198; Proctor et al., (1995) MPMI 8:593-601] which can inhibit amino acid incorporation and protein production in plant tissues [Casale et al., (1988)
Phytopathology
78:1673-1677]. This toxin is also implicated in adversely affecting the growth of mammalian cells [Knasmüller et al., (1997)
Mutation Research
391:39-48]. DON is retained in semolina at approximately 50% and
F. graminearum
has a strong adverse effect on pasta color when Fusarium damaged kernels make up as little as 2% of a lot [Dexter et al., (1997)
Cereal Chem
. 74:519-525]. Additionally,
G. zeae
infected kernels can contain the estrogenic toxin zearalenone. Grain contaminated with either of these mycotoxins often is downgraded or can not be sold [Tuite et al., (1990)]. Contaminated grain is frequently unsuitable for human consumption and may be refused as feed [Vesonder et al., (1980)
Process Biochem
. 16:12-15]. The importance of FHB was recognized by the 105th U.S. Congress when it adopted the “Wheat and Barley Protection Act” that authorized expenditure of 26 million dollars for the study of FHB.
This invention relates to two
Bacillus species
that are effective antagonists of Fusarium head blight.
2. Description of the Prior Art
Though some success in controlling FHB can be expected by plowing fields to bury crop residues infested with
F. graminearum
after harvest [Bai et al., (1994)
Plant Dis
. 78:760-766], minimal tillage practices render this alternative unacceptable. Some progress has been made in finding and analyzing scab resistance in wheat, though all cultivars in current production are susceptible [Bai et al., (1994)]. Foliar fungicides applied at anthesis can be useful in reducing scab [McMullen, (1998) Fungicide technology network of the National FHB initiative—1998 Report. Proceedings of the 1998 Head Scab Forum, Michigan State University, October 26-27, pp.47-49], but few fungicides are registered for use on wheat this late in the growing season [Shaner et al., (1992)
Fungic. Nematicide Tests
. 47:206-207]. Additionally, costs and concerns in the public and private sectors over pesticide residues in the environment and in food products render this disease control alternative less attractive.
Biological control, though currently not available, would be an environmentally acceptable method for substantially decreasing the level of disease incited by
G. zeae
. Though biological control agents (BCA's) have become a more acceptable control alternative for plant pathogens and BCA products are being marketed to a greater extent than ever before [Fravel et al., (1996)
Biological and Cultural Tests
11:1-7] to date there have been few attempts to develop strategies and microorganisms for biologically controlling FHB [Stockwell et al., (1997)
Phytopathology
87(6):S94; Perondi et al, (1996)
Fitopatologia Brasiliera
21:243-249]. The life cycle of
G. zeae
suggests that the pathogen is especially susceptible to control using applied microorganisms at anthesis through the soft dough stage of kernel development, when the majority of wheat head infection by
G. zeae
is generally considered to occur [Andersen, (1948) Phytopathology 38:595-611; Arthur, (1981)
Indiana Agric. Exp. Stn. Bull
36:129-138]; Fernando et al., (1997)
Phytopathology
87(6):S30 (Abstr.)].
Luz et al. [5
th
International Congress of Plant Pathology, Abstracts of Papers, p. 348 (1988)] reports in vitro screening in excess of 300 bacteria and yeasts isolated from wheat against
F. graminearum
. Likewise, Perondi et al. [Anais do 2° Simposio de Controle Biológico, Brasilia, DF, p. 128 (Abstr., 1990);
Fitopatologia Brasiliera
21:243-249 (1996)] reported testing microbial strains as possible antagonists against
F. graminearum
. Promising strains selected by the funnel method and tested in greenhouse studies were shown by Luz et al. [
Fitopatologia Brasiliera
15(3)246-247 (1990)] to diminish the severity of wheat scab between 7 and 31% when compared to the control.
SUMMARY OF THE INVENTION
We have now discovered two Bacillus strains that are superior antagonists of
F. graminearum
and will suppress FHB (Fusarium head blight, also known as scab) in cereals. These antagonists were initially selected from a pool of more than 700 strains obtained from anthers of wheat. They were selected based upon their ability to control mycelial growth of
F. graminearum
in plate culture and for their ability to reduce the incidence of FHB when bioassayed in the seed head of wheat.
In accordance with this discovery, it is an object of this invention to provide two novel microbial strains that suppress the profusion of
F. graminearum
in seed heads of cereal, particularly in wheat and barley.
This and other objects of the invention will become readily apparent from the ensuing description.
DEPOSIT OF BIOLOGICAL MATERIAL
Purified cultures of the two Bacillus species identified as being effective antagonists of
F. graminearum
have been deposited on Sep. 7, 1999 in the U.S. Department of Agriculture, Agricultural Research Service Culture Collection in Peoria, Ill., under the terms of the Budapest Treaty. Accession Numbers for these deposits are as follows:
AS 43.3
NRRL B-30210
Bacillus sp.
AS 43.4
NRRL B-30211
Bacillus sp.
REFERENCES:
Perondi et al., Fitopatologia Brasileira, (1996) vol. 21, No. 2, pp. 243-249.*
Hu et al., Weishengwuxue Tongbao (1996), 23(6), 323-326.*
N. I. Khan et al., “Developing strategies and organisms for biocontrol of head scab of wheat”, Phytopathology 88:S47 (1998).
N.I. Khan et al., “Biological control of scab of wheat incited byGibberella zeae”, proceedings of the 1998 National Fusarium Head Blight Forum, Michigan State University, East Lansing, MI, pp 45-46, Oct. 26-27 (1998).
N. I. Khan et al., “Performance of selected antagonists of Fusarium head blight against a range ofGibberella zeaeisolates,”, Phytopathology 89:S39 (1999).
D. A. Schisler et al., “Selection and evaluation of microbial antagonists active againstGibberella zeae, a causal agent of Fusarium head blight in wheat”, proceedings of the 99thGeneral Meeting of the American Society of Microbiology, pp. 575 (1999).
W. C, da Luz et al., “Biocontrol of fungal pathogens of wheat with bacteria and yeasts”, proceedings of the 5thInternational Congress of Plant Pathology, Kyoto Japan, pp. 2-134, Aug. 20-27 (1988).
W. C. da Luz et al., “Seed microbiolization for control o
Boehm Michael J.
Khan Naseem I.
Schisler David A.
Fado John D.
Marx Irene
Ribando Curtis P.
Silverstein M. Howard
The United States of America as represented by the Secretary of
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