Chemistry: molecular biology and microbiology – Treatment of micro-organisms or enzymes with electrical or... – Modification of viruses
Patent
1993-09-02
1996-02-27
Fox, David T.
Chemistry: molecular biology and microbiology
Treatment of micro-organisms or enzymes with electrical or...
Modification of viruses
47 58, 4352404, 435 691, 435 701, 514 2, 530370, 536 232, 800205, A01H 104, A01H 1500, A01H 2500, A01H 6300, C07H 2104, C12N 1500
Patent
active
054948134
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the control of pests. In particular the invention relates to the protection of plants against parasitic nematodes.
BACKGROUND OF THE INVENTION
Most plant parasitic nematodes are less than 2 mm in length and develop from an egg through three or four juvenile stages (J1-J3 or J4) to adult in a life cycle lasting from a few weeks to several months. Ectoparasites and endoparasites occur and more species attack roots than aerial tissues. With very few exceptions, the nematodes use a hollow stylet both to pierce plant cell walls and to withdraw cell contents. Migration in the plant involves intracellular penetration through perforated cell walls or bodily movement between cells. Some endoparasites migrate short distances into plants before feeding whereas others move continually or rely on host growth to assist their distribution within the plant.
Several genera including both the economically important cyst and root-knot nematodes modify plant cells into feeding sites able to support sedentary females. Such individuals grow within a few weeks by up to 1000.times. ensuring a high fecundity.
Cyst nematodes (principally Heterodera and Globodera spp) are key pests of major crops. Heterodera glycines is the principal pathogen of soybean in the USA with an economic effect that may lie between US$500-1000M a year. Heterodera shachtii (Beet cyst nematode) is a major constraint on sugar beet growers in the EC and parts of the USA and Heterodera avenae (cereal cyst nematode) is a cosmopolitan pathogen of cereals with particular importance in more arid soils for instance parts of Australia. Potato cyst nematodes Globodera rostochiens and G. pallida occur in many areas of potato cropping. They are highly damaging causing an estimated .English Pound.10-50M a year loss to the UK potato industry from their direct and indirect effects on production.
Root-knot nematodes (Meloidogyne spp) are associated with tropical and subtropical soils and few other pathogens out rank them in importance to world agriculture. There are many species but five are responsible for the majority of crop damage with M. incognita estimated to account for about 66% of all incidences of economic loss to this genus. Severity of crop losses varies but overall losses of 11-25% have been estimated for a wide range of crops in major geographical regions of the tropics.
Cultural, chemical and resistant control are the chief approaches in current use, often in an integrated manner. There is an urgent need to improve control since nematicides are among the most unacceptable compounds in widespread use. One carbamate, aldicarb and its breakdown products are highly toxic to mammals and have polluted groundwater in the USA and presumably other areas where this pesticide is widely used. Cultural control includes hidden losses that are unacceptable to specialist growers or those with few alternative, economic crops. Resistant cultivars are not always available and are often out yielded by the best susceptible cultivars so again they involve hidden losses unless nematode damage is certain to occur. The inadequacy of current crop protection testifies to the need for an effective approach to the control of nematodes.
Economic densities of cyst nematode characteristically cause stunted plants with a root system occupying a small soil volume. The diseased plants show symptoms of mineral deficiencies in their leaves and wilt readily. Yield losses are related to the severity of parasitism above a tolerance limit and can be substantially above 50% for some species. Root knot nematode causes many of the effects described for cyst nematodes with the addition that the root system is often heavily galled with increased accessibility to secondary pathogens.
A few nematodes are vectors of a narrow range of plant viruses (NEPO viruses by, Xiphinema, Longidorus, and certain TOBRA viruses by, Trichodorus). For example, Xiphinema spp. transmit the GFLV virus to vines. In addition nematodes in association with fungi are transmitted
REFERENCES:
Ryan. 1990. Annu. Rev. Phytopathol. 28:425-449.
Miller et al. 1977. Journal of Nematology, 9(3):192-197.
Potrykus. 1991. Annu. Rev. Plant Physiol. Plant Mol. Biol. 42:205-225.
Bowles et al. 1991. Proc. Phytochem. Soc. Eur. 32:225-236.
Hilder et al. 1987. Nature. 330: 160-163.
Brunke et al. 1991. Tibtech. 9:197-200.
Atkinson Howard J.
Hepher Andrew
Fox David T.
Nickerson Biocem Limited
Veitenheimer Erich E.
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