Drug – bio-affecting and body treating compositions – Whole live micro-organism – cell – or virus containing – Bacteria or actinomycetales
Reexamination Certificate
1999-04-12
2001-10-23
Witz, Jean C. (Department: 1651)
Drug, bio-affecting and body treating compositions
Whole live micro-organism, cell, or virus containing
Bacteria or actinomycetales
C424S093100
Reexamination Certificate
active
06306390
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a root endophyte capable of preventing soil-borne diseases, a process for producing said root endophyte, and a method for preventing soil-borne diseases of crops using said root endophyte.
BACKGROUND ART
Continuous cropping causes impairments such as poor growth, reduction of the yield, and deterioration of quality in many crops. Severe impairments sometimes result in death of plants. These impairments resulting from continuous cropping are attributed mainly to soil-borne diseases.
For example, club roots and the yellows of Chinese cabbages are representatives of the soil-borne diseases of Chinese cabbages. The club roots of Chinese cabbages are caused by
Plasmodiophora brassicae
. The fungal spores invade into the roots of Chinese cabbages cultivated on the soil, proliferate there, thereby causing the club root disease. As the name of the disease indicates, clubs are formed in the roots of Chinese cabbages suffering from the disease and the clubs inhibit uptake of water and nutrients by the plants from the soil. Eventually, the growth of Chinese cabbages becomes poor, which leads to reduction of their yield and quality. The yellows of Chinese cabbages is caused by
Verticillium dahliae
, which is a terrestrial fungus. Its spores invade into the roots of Chinese cabbages cultivated on the soil, proliferate there, and cause the yellows. In this disease,
Verticillium dahliae
inhibits formation of chloroplasts in the crop, generation of carotenoid alone progresses, then the plants yellow. As a result, the growth of Chinese cabbages becomes poor, resulting in reduction of their yield and quality. Moreover,
Verticillium dahliae
infects flowers and vegetables other than Chinese cabbages. For example, it causes Verticillium wilt in eggplants and tomatoes.
Conventionally, soil has been disinfected generally using chemicals such as PCNB to prevent soil-borne diseases. However, continuous use of soil fumigants subsequent to continuous cropping has facilitated advent of novel pathogens in the soil, which are highly resistant to soil fumigants. Thus, the efficacy of soil fumigants for the pathogen control is reduced. In addition, chemically synthesized soil fumigants may possibly give harmful influences on the environment encompassing consumers, producers, and ecosystem. Under these circumstances, the use of fumigants tends to decrease.
Recently, attempts have been made to apply biological control, which is regarded as a safe method to prevent soil-borne diseases. The biological control has been performed using fungi such as Trichoderma, Fusarium, bacteria such as Pseudomonas and Bacillus, and actinomycetes such as Streptmyces. These microorganisms are formulated into agents and put into practice mainly in United States. Prevention of various soil-borne diseases by utilizing these microorganisms has been studied, but practically usable effect has not been obtained yet.
These microorganisms generally grow and inhabit in the rhizosphere (many microorganisms live within the soil of a few millimeter thick surrounding the surface of roots of plants), and they prevent soil-borne diseases. Since rhizosphere, which is an interface between roots of plants and soil, is a complex and unstable environment, the stable preventive effect is hardly obtained in many cases. It is difficult to constantly obtain a sufficient preventive effect, particularly, in Japan, where a wide variety of microorganisms live in the soil. Prevention of soil-borne diseases targeting rhizosphere has not been widely spread among farmers.
DISCLOSURE OF THE INVENTION
As described above, soil disinfection using agricultural chemicals such as PCNB is not able to completely prevent soil-borne diseases of crops. Furthermore, such soil disinfection gives an undesirable influence on the environment encompassing humans and the ecosystem. Even the conventional biological control has a problem that the preventive effect cannot be constantly obtained when rhizosphere is targeted as an action site for pathogens. An objective of the present invention is to provide techniques for preventing soil-borne diseases with a constant effect and without harmful influences on humans and environment.
There exist a variety of microorganisms in the soil and plants, and they live with interacting with each other. Most of these microorganisms are non-pathogenic and are not infectious to host plants. Particularly, symbiotical root endophytes (symbiotes) are known to live in the root of plants without causing diseases. Focusing on the characteristics of the root endophytes, the present inventors thought that a novel technique for biological control can be established by changing an action site (battlefield) between pathogenic microorganisms causing soil-borne diseases and endophytes from rizhosphere, which is largely affected by environment, to the inside of roots, which is less affected by environment.
Based on this concept, the present inventors first isolated root endophytes from roots of Chinese cabbages, and investigated a preventive effect on the yellows of Chinese cabbages. Specifically, the inventors isolated symbiotic root endophytes from the root of Chinese cabbages cultivated in the soil free from agricultural chemicals, and cultured them. The root endophytes were identified based on the morphology of their spores, and the microorganisms that could not be identified were classified based on colony types. The culture media of these microorganisms were inoculated with seeds of the Chinese cabbages to allow the seeds to germinate. The root endophytes capable of preventing soil-borne diseases of Chinese cabbages were then inoculated into the roots of the Chinese cabbages.
Verticillium dahliae
was then inoculated into the soil where the Chinese cabbages were grown and the Chinese cabbages were continuously cultivated for a period required for the onset of the yellows. Whether the yellows developed in the Chinese cabbages was examined and the root endophytes that were inoculated into the roots showing a low incidence rate of the yellows were identified and selected. As a result, the inventors found that some of the root endophytes inoculated into the roots of the Chinese cabbages remarkably prevented the yellows. In other words, the yellows never developed or the incidence rate of the yellows was remarkably low. Among the root endophytes having the ability to prevent yellows of Chinese cabbages,
Heteroconium chaetospira
was found to be particularly effective to prevent the yellows of Chinese cabbages.
The inventors also examined whether
Heteroconium chaetospira
prevents not only the yellows but also club root diseases of Chinese cabbages, cabbages, and ‘chingensai’. Specifically, the culture medium of
Heteroconium chaetospira
was inoculated with seeds of these plants to germinate the seeds. The roots of the plants were then allowed to be inoculated with the fungus. Pathogenic fungus of the club root disease were inoculated into the soil on which the plants were grown and the plants were subsequently allowed to grow for the period required for onset of the club root disease. The development of the disease was then examined. As a result, the inventors found that
Heteroconium chaetospira
notably prevented the club root disease as well as the yellows in Chinese cabbages, cabbages, and ‘chingensai’.
Furthermore, the inventors found that, when
Heteroconium chaetospira
inoculated into the roots of the plants including seven species of Cruciferae, two species of Solanaceae, two species of Cucurbitaceae, Umbelliferae, Asteraceae, Malvaceae, and Chenopodiaceae, the fungus inhabited there as in the case of Chinese cabbages, cabbages, and ‘chingensai’.
The present invention relates to a root endophyte capable of preventing soil-borne diseases, a process for producing the root endophytes, and a method for preventing soil-borne diseases of crops using the root endophytes. More specifically, it relates to:
(1) a root endophyte symbiotically living in roots of crops in the soil and capable of preventing
Fish & Richardson P.C.
Ibaraki Prefecture
Witz Jean C.
LandOfFree
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