Drug – bio-affecting and body treating compositions – Whole live micro-organism – cell – or virus containing – Fungus
Reexamination Certificate
1999-09-29
2002-12-17
Witz, Jean C. (Department: 1651)
Drug, bio-affecting and body treating compositions
Whole live micro-organism, cell, or virus containing
Fungus
Reexamination Certificate
active
06495133
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a new strain of
Gliocladium roseum
fungus, referred to as ACM941 that is capable of controlling plant diseases. In particular, the present invention relates to the use of the new strain of
Gliocladium roseum
fungus as a biological control agent (sometimes referred to as bioagent) to inhibit soil-borne and seed-borne fungal pathogens and to enhance plant growth and productivity in both greenhouse and field conditions.
2. Description of Related Art
Soil-borne and seed-borne fungal pathogens of plants are responsible for severe economic losses in the agricultural and horticultural industries worldwide. These pathogens cause plant diseases such as seed decay, root/foot rot, seedling blight and wilt. Such diseases commonly reduce emergence, plant vigor and yield potential. Severe disease infection can kill emerging seedlings of an entire plant population, and result in a total loss of crop yield.
Solutions to the recurring problem of plant pathogens have been explored for decades. As particular crops become more abundant, and the area of land allocated for agriculture expands, there is an inherent need to employ more efficient and effective farming practices. As a result of increasing demand for crop production, farmers must often compromise their cultural practices by planting crops on sub-optimal land, or by increasing the frequency at which crops are planted in a specific location. In doing so, crop nutrients are depleted and specific crop pathogens, especially soil-borne or seed-borne pathogens, become more prevalent. Accordingly, it is increasingly difficult to sustain the health and productivity of a respective crop.
Historically, preferred cultural practices and chemical controls were used in combination to combat destructive pathogens. More recently, the use of integrated systems employing biocontrol agents and chemicals has become more prevalent.
1
(note: all superscript reference numerals relate to a list of references appearing at the end of this disclosure). However, despite progressive research in recent years, chemical alternatives remain the most reliable and economic solution to the problems caused by most soil-borne and seed-borne plant pathogens.
The case of field pea is illustrative. There were approximately 900,000 hectares of field pea in western Canada in 1998, estimated at a total farm value of over $400,000 million. In recent years, the field pea crops of western Canada have been most affected by soil-borne or seed-borne diseases, as well as the Ascochyta complexes of root and foliage. Known as PRRC (pea root rot complex) diseases, the soil-borne and seed-borne diseases are most commonly caused by the pathogens
Fusarium solani
f.sp. pisi,
Fusarium oxysporum
f.sp. pisi,
Mycosphaerella pinodes, Rhizoctonia solani, Sclerotina sclerotiorum, Aphanomyces euteiches, Alternaria alternata
and Pythium spp. The incidence of PRRC diseases varies with year and location, while its severity is largely dependent on climate, crop rotation and cultural practices. The yield losses of pea crops alone, as a result of PRRC pathogens including foliar infection by Ascochyta complex, are frequently devastating with a conservative 15% yield reduction translating into an approximate annual loss of $60 million in areas of western Canada. As crops such as pea become increasingly important, efforts must focus on more effective and efficient means of crop farming, both in Canada and around the world.
The most effective solution to the destruction of crop plants by pathogens would most likely be the development of resistant cultivars, which would allow for plant growth and productivity in the presence of fungal pathogens. Unfortunately, success in the development of PRRC resistant cultivars of pea, or other resistant crop cultivars, has not been forthcoming. Alternatively, biological control of crop plant pathogens by microorganisms may be considered a more natural and environmentally friendly alternative to existing chemical treatment methods. Accordingly, it is desirable to isolate a microorganism, which displays antagonistic effects against a target pathogen, and is capable of survival and propagation in a target location.
Efforts to isolate antagonistic microorganisms effective against plant pathogens have been underway in recent years. As a result, several microbial isolates have proven effective as plant pathogen antagonists and some related biocontrol products are currently commercially available, including: Mycostop™ (Streptomyces sp.); GleoGard™ (
Trichoderma virens
); Kodiak™ (Bacillus sp.); and BioTrek™ (Trichoderma sp.); TRICHODEX™ (
Trichoderma harzianum
); and BINAB-T™ (
T. harzianum
plus
T. polysporum
).
The effectiveness of bioagents against certain pathogens has been characterized according to a variety of modes of action. Cook et al.
2
described the modes by which a bioagent can effectively act against target pathogens as including: (i) a parasitic attack against the pathogen, (ii) a competitor for a common food source, (iii) a source of toxic antibiotic substances, or (iv) an induced indirect toxic effect by the release of volatile substances. As such, a bioagent behaves as a natural antagonist to the pathogen.
Although efforts have concentrated on the biological control of PRRC pathogens, obstacles in stability, delivery and versatility have not been resolved. Specifically, Hwang et al.
3
in 1992 reported the potential use of
Gliocladium virens
(Syn.
Trichoderma virens
) as a biocontrol agent against Rhizoctonia caused root rot in field pea, when employed with a fungicide. In this integrated control system, the presence of the fungicide provided protection against the pathogen when the environmental conditions inhibited the activity of the bioagent. Parke et al.
4
in 1991 disclosed findings of the effectiveness of
Pseudomonas cepacia
and
P. fluorescens
against Pythium damping-off and Aphanomyces root rot in pea when applied to seed.
P. cepacia
was disclosed as being the most effective bacterium, increasing emergence by an average of 40% and yield by 48% over captan fungicide alone. The Parke et al. reference further reported on disclosures of the effectiveness of seed treatment with species of Trichoderma
5
and
Penicilium oxalicum
6
against diseases of pea Oyarzun et al.
7
further reported findings, in 1993, of the biological control of root rot in pea caused by
Fusarium solani,
with two nonpathogenic
Fusarium oxysporum
isolates. Both isolates of
F. oxysporum
investigated displayed reduced disease severity and prevented the plant weight losses owing to
F. solani
f. sp. pisi in sterilized soil. In 1996, Xi et al.
8
reported on the effectiveness of formulated Rhizobacteria against root rot of field pea.
Pseudomonas fluorescens
(strain PRA25) peat-based granular formulation increased yield by 17% over untreated, in a trial with light disease infection, and by 120% in another trial with moderate infection.
P. cepacia
(strain AMMD) and
P. fluorescens
increased seedling emergence, and decreased disease incidence and severity. However, these agents had variable effect on yield when disease level was light to moderate. In addition, biocoritrol agents resulted in only limited control when disease was severe. As a result, a commercially available microbial product for the treatment of root rot diseases of pea is not currently available.
8
U.S. Pat. No. 5,165,928, issued on Nov. 24, 1992 to Cornell Research Foundation, Inc. and entitled “Biological Control of Phytophtora by Gliocladium”, discloses the use of strains of
Gliocladium virens
(Syn.
Trichoderma virens
) on the root biosphere of plants in controlling plant diseases caused by
Phyrophthora sojae.
More specifically, this patent is directed to the use of specific strains of
T. virens
on
P. sojae
-caused stem and root rot in soybean plants.
Steinmetz and Schobeck
9
(1993), reported the use of conifer bark inoculum, comprising
Trichoderma harzianum
or
Gliocladium roseum,
in controlli
Battison Adrian D.
Dupuis Ryan W.
Her Majesty the Queen in right of Canada as represented by the
Williams Michael R.
Witz Jean C.
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