Multicellular living organisms and unmodified parts thereof and – Plant – seedling – plant seed – or plant part – per se – Higher plant – seedling – plant seed – or plant part
Reexamination Certificate
1996-06-20
2001-11-06
Campell, Bruce R. (Department: 1661)
Multicellular living organisms and unmodified parts thereof and
Plant, seedling, plant seed, or plant part, per se
Higher plant, seedling, plant seed, or plant part
C047S05810R
Reexamination Certificate
active
06313377
ABSTRACT:
The present invention relates to treated primed seeds having a longer shelf life than conventionally primed seeds, a process for obtaining such seeds and plants derived therefrom.
Primed seeds and methods for obtaining them are known in the art.
Primed seeds are generally capable of a faster germination over time and display better synchronization in germination, than non-primed seeds.
Conventional seed priming processes are i.a. disclosed by EP 309 511 B1 and EP 254 569 B1.
The present invention provides a method of treating primed seeds which results in a prolongation of shelf life compared to optionally dried back conventionally primed seeds of the same species having substantially the same moisture content (MC) chatacterised in that the primed seeds are subjected to a water stress, a heat treatment or a combination thereof and are subsequently—where—desired—dried back to a desired MC.
The drying back of the seeds as abovementioned, involves a reduction in the seed MC. The drying back may be to any desired MC. In a preferred embodiment the drying back is to a MC of untreated seeds, i.e. dry seeds which have not been primed.
Hereinafter the terms MC and water content will be used interchangeably. The MC will be given in percentage terms, based on seed fresh weight(unless otherwise stated).
The water stress may be achieved by any manner known in the art which will result in the seeds having a lower MC.
In general a water stress will be obtained by reduction of the MC of conventionally primed seeds by 5% units or more, i.e. to 20% or less, if the conventionally primed seeds have an initial MC of 25%, or to 50% or less if the conventionally primed seeds have an initial MC of 55%. More specifically, the water stress will in general be achieved by reduction of the MC by 5% units up to 20% units, whereby, it is in general advantageous not to reduce the MC to a value below 15%.
The water stress should be maintained for a longer period of time, in general 1 to 7 days, depending i.a. on the temperature, whereby the optimum conditions will depend on the seed species and can be determined by standard tests. It will be appreciated that this can be achieved by maintenance of the MC of the conventionally primed seeds constant at the desired reduced level (i.e. conveniently 5 to 20% units below the MC of conventionally primed seeds) or by drying the conventionally primed seeds slowly enough for them to remain sufficiently long under water stress.
Accordingly prolonged shelflife may be attained by incubation of the primed seeds at a water potential which induces a water stress, by slow MC reduction of primed seeds, by an initial quick MC reduction of primed seeds up to a MC where the seeds are still subject to water stress, followed by incubation or slow MC reduction of the thus obtained partly dried primed seeds or by a heat shock. Slow MC reduction can be achieved in a manner known per se, e.g. by drying under mild conditions or by bringing the primed seeds in contact with an osmoticum that is not toxic to the seeds and having a water potential below O MPa. The description of processes (a), (b) and (c) hereinafter, illustrates typical conditions for subjecting primed seeds to a water stress.
The water stress may be achieved by:
a) slowly drying prim ed seeds at a temperature of from 3 to 40° C. for 3 to 7 days, or
b) reducing the MC of primed seeds under conventional drying conditions by 5 to 20% units and storing the thus dried seeds for 1 to 7 days in a container with minimal air and moisture exchange, at a temperature of from 3 to 40° C. or
c) incubating primed seeds in an osmoticum for 1 to 7 days at a water potential chosen to reduce the MC of the primed seeds by 5 to 20% units.
The heat treatment may be achieved by subjecting primed seeds to a heat shock in the range of from 25 to 45° C. for from about 1 to 5 hours.
The seeds produced according to the processes of the invention, have greater desiccation tolerant embryos than conventionally primed seeds, in that the former survive longer storage periods under ambient storage conditions as hereinafter defined.
By a seed comprising a desiccation tolerant embryo is meant a seed in which a reduction in the MC of the seed to a value typical for dehydrated seeds e.g. of about 5 to 7%, does not substantially adversely affect the seeds viability, the viability being measured in terms of its ability to germinate when placed under suitable growing conditions or after an appropriate standard test, e.g. a controlled deterioration test (see hereinafter) either before or after a prolonged storage period at ambient storage conditions.
The embryo of the seed is taken to means structures which are necessary for the development of the seed, such as the cotyledon, acis and non-emerged radicle tip and which collectively, or in part are able to acquire a desiccation tolerance.
Primed seeds can be stored for a number of weeks at about 5° C. but are unsuitable for storing for extended periods of time under ambient storage conditions.
By the term primed seed is meant (insofar as not otherwise stated), that the seed has been subjected to conventional priming techniques as hereinafter discussed, it has a MC in the range of from 20 to 55% (depending on species) and has a desiccation tolerance typical of conventionally primed seed. It will be appreciated that all non-primed seed is desiccation tolerant i.e can survive drying, the extent of desiccation tolerance being species dependent. On priming according to conventional processes, the seed becomes less desiccation tolerant, the loss in desiccation tolerance increasing with the increase in period of priming, until a point at which the seed can no longer be said to be desiccation tolerant, this complete loss of desiccation tolerance occurring at the point of germination of the seed. The processes of the present invention, as hereinafter described, are applied to non-germinated seed which has been primed according to conventional priming processes. Non-germinated seed is defined herein as seed in which the radical and/or hypocotyl has not protruded or emerged from the seed coat or pericarp. The radical and/or hypocotyl may have caused the seed coat to split or crack, however it will not have protruded through the split or crack. The endosperm surrounding the embryo. may be visible through the split or crack. Non-germinated conventionally primed seed to which the proceeses of the present invention have been applied, will hereinafter be referred to as as treated seed(s). Non-germinated conventionally primed seed(s) to which the processes of the present invention have not been applied, will hereinafter be referred to as conventionally primed seed(s). Commercially acceptable seed(s) which have not been primed, shall be referred to as untreated seed(s).
It is also possible to determine the stage of the germination process by physical parameters, e.g. size, volume or denity In this way, a selection can be made of seeds to be treated according to the invention.
Thus as is demonstrated below, treated seed has a longer shelf life than conventionally primed seed of the same species and MC. The longer shelf life can be demonstrated by measuring % germination under the same or similar conditions e.g standard growing conditions (as below defined), after either a controlled deterioration test, or storage under ambient conditions, the treated seed having higher % germination of normal plants compared to conventionally primed seed which have been subjected to the same controlled deterioration test or storage conditions.
By standard growing conditions is meant a temperature in the range of about 15 to 20° C. in the presence of air and water.
The term shelf life as used herein may be expressed in terms of viability (i.e. in terms of ability to germinate and give rise to normal plants after storage under ambient storage conditions, for example after subjection to a controlled deterioration (CD) test (Tarquis A. M. & Bradford K. J., J. Exptal. Bot. Vol. 43, 1982, No. 248,pp. 307-317). The viability of seeds subjected to the CD-tes
Bruggink Tonko
Schipper Job
Van der Toorn Peter
Campell Bruce R.
Para A
Syngenta Participations (AG)
Vrana Bruce
Wyner Lynn Marcus
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