METHOD FOR TREATMENT OF DISEASE IN PLANT MATERIAL

Abstract: A method for treatment of disease in plant material. The method involves subjection of the plant material, especially seed material, to elevated temperatures (less than 55`C) at pressures other than atmospheric. The method may also involve simultaneous treatment with suitable chemicals.

Description: :ISTHOD ?OR TR Ag:s::τ OF ISEAS I:: I.-J:U? I^I HI^L 3ACKv_5.CUI3 0? TΞ3 11773:7210 :: 1. .Field of the Invention The present invention relates τo a method for the treatment of plant material for purposes of the eradication therefrom, or at least a reduction in the degree of incid¬ ence therein, of damaging or potentially damaging disease. 2. Description of the Prior Art Plant material, regardless of type, is generally susceptible to the ravages of a.number of diseases. Such diseases nay manifest themselves in a manner which will serve to make the plant itself unsightly and hence effect¬ ively unsuitable for sale, display, use or other-rise. G-enerally speaking in such a situation a diseased plant will also not be suitable for purposes of propagation, by reason of the fact th?.t the disease present in the so-called "parent" plant will more often than-not be transmissible to subsequent generations. Investigation has also shown that, generally speaking at ' least, diseases of the type under con¬ sideration are transmissible from an infected to a previously "clean" or uninfected neighbouring plant, by means of wind action, water action, contact etc. Growers are therefore faced with the problem of effectively isolating infected growing areas from previously "clean" or uninfected areas - a difficult problem indeed. As the level or derree of in¬ fection increases, -"rowers are also faced with the problem of locating "clean" growing areas, whereby to satisfy the demand for their crop. Investigations have she ** . * -! that, with certain types of plant fungal diseases, a growing area once tainted will remain unusable for a substantial period of time (perhaps several crowing seasons or mere) ~ cy reason of what may be termed a residual effect of the infection. This residual infection in turn increases the likelihood of sub- sequent infection in surrounding areas - by reason of water action etc. (as stated earlier). O PI As such, it can be seen that the *" effect of disease in plant material is, generally speaking, rather far-reaching involving insofar as the grower is concerned an immediate loss of revenue iy reason of lost production, a future loss in terms of breeding or propagation potential, not to mention the loss of growing area and the need for the location and maintaining of new, infection-free areas. Insofar as re¬ tailers and consumers are concerned, the result will be a reduction in the uality and/or volume of material (product) available for sale and purchase, with the subsequent and inevitable increase in price etc. • Throughout the ensuing description attention will be directed specifically to a method for the treatment of potatoes with a view to eradicating therefrom or reducing the degree of incidence therein of the disease commonly known as "powdery scab" (spongospora subterranea) . It should be understood, however, that the invention is not to be restricted solely to such a usage. Indeed the method in accordance with the present invention would be equally suitable for the treatment in potatoes of diseases such as common scab, pho a, Blackleg, Puεariums, Ehizoctonia, Silver Scurf and other skin complaints. Furthermore it should be understood that the method in accordance with the invention will also be suitable for use in the treatment* of disease in other plant material, be such material in the form of veg¬ etables, fruit or any other plant matter. Insofar as the especially preferred embodiment involving the treatment of "po er scab" in potatoes is concerned, it should be noted that such a disease is becoming increasingly prevalent on or in potato crops here in Australi This disease manifests itself in unsightly "scab" areas or * . the surface of the potato itself. This "scab" in itself has a three-fold effect. irstly, the unsightly nature thereof re d uces substantially the chances of sale, use etc. of infected articles. Secondly, it ultimately results in breaking of the skin of an infected pc ato, thereby allowing OMPI for ingress to the interior of the vegetable of other organisms which in their turn will lead to ultimate des¬ truction, as for example by rotting, of the overall potato. Thirdly, the "scab" has been found in practice to be especially suited for "carrying", so to speak, a number of associated and more serious plant diseases, such as for example various forms of destructive blights, so-called mop-top virus, pink rot, and the dreaded Irish blight. The disease known as "powdery scab" is further- more significant by reason of its capability of being trans ported, as by wind, water etc., from an infected growing area to a previously untainted area, thereby spreading the disease. In addition, once an area is tainted or infected there is a residual effect, such that a previously infected area will remain tainted for a substantial period of time. In the long-term, therefore, the disease if allowed to go unchecked will result in effectively continuous infection in an ever-increasing area and on an ever-increasing scale. The consequences of this will be disastrous to the grower, not to mention the retailer and/or the consumer. In the past a number of different methods have been tried to overcome, that is eliminate altogether or at least reduce, the problems posed by the disease known as "powdery scab". However, these prior art methods have proven not particularly successful for a variety of reasons, as will be explained in more detail hereinafter. One method previously employed involves the use of chemicals, to be sprayed or otherwise disposed over a crop-growing area. Such a procedure was found to produce non-uniform results and indeed to provide only transient relief from the problem at hand. Furthermore this method was found to be both wasteful of chemicals and accordingly expensive, in fact uneconomical. Experience also has shown that the effectiveness of such treatment was very much dependent upon timing, in that the disease has been shown to be in some ways impervious to chemical attack except OMPI WIPO at certain specific stages during its life ' cycle . In addition with such a method there always exists the poss¬ ibility of danger to human and animal life oy the spraying of chemical material. Another method tried employs a dipping process, with seed potatoes (for example) being dipped in a chemical bath, involving chemicals considered destructive to the relevant disease micro-organisms. Such a dipping procedure has also been found to be unsatisfactory in that generally speaking the chemicals employed were found not to have penetrated sufficiently far into the potatoes being treated to destroy the disease-causing micro-organisms, this despite the fact that diseases such as, for example, "pc-wάery scab", manifest themselves primarily if not solely in the outermost surface layers of a potato. Attempts are being made to breed varieties of potatoes exhibiting an increased resistance to the disease. , However, success with such attempts is seemingly a long way off yet, and meanwhile the disease is spreading in a substantially uncontrolled manner. Furthermore, there is every chance that any such resistant varieties evolved will provide only a temporary * - solution to the problem, with future generations bred from such varieties exhibiting less and less resistance to the disease, or alternatively with different strains of the disease itself evolving, strains against which the so-called resistant varieties of potatoes would not be proof. 5U-LI_ύtY OF THE IITYEI-TIOIT The problem is, therefore, to devise a method for treating tainted or infected seed potatoes, for example, such that the contamination is eliminated or at least greatly reduced., whereby to allow for planting in previously untainted ground. Furthermore the invention seeks to provide a method of tr atment which will allow for p lanting even in previously contaminated ground without risking later contamination of the crop -• τ*τ •* -' * > +v- ; The present invention seeks to provide, therefore, a method for the treatm nt of plant material which is res¬ ponsible for both an i:.mediate (or short-term) and a long- term result. To be more specific the present invention relates to a method for the treatment of plant material which will result in a reduction in the incidence of disease, and preferably total eradication of that disease, from a first generation plant, at the same time making such a first --eneration lant suitable for purposes of breeding or prop- a-tating subsequent generations of at least e uivalently disease-free plant materia.1. The present invention furthermore seeks to provide a method for the production of a subst ntially. ** disease-free variety of plant material, exhibiting a resistance (of sorts) to plant isease, thereby allowing for the planting thereof even in previous "tainted" or infected growing areas. As such, the method in accordance with the present invention will provide propagating material suitable not only for use in "clean" growing areas, but also in previously tainted areas, there'03- allowing such tainted areas to be restored to growing condition or utility. In accordance with the present invention there is provided a method for the treatment cf plant seed material, said method involving Vζ.e subjection of the plant seed material to elevated or reduced temperatures, at a pressure other than atmospheric. In order that the invention may be more clearly understood, and put into practical effect there shall now be described in detail an especially preferred method of treatmen cf plant material in accordance with the invention. The description is -riven by way of non-limitative example only and is specifically directed to the treatment of so-called powdery scab in potatoes. __3 stated earlier in this spec¬ ification, however, the method in accordance with the present invention will be equally well suited to the treatment of various other lant diseases. BAD ' V/hen used in relation to potatoes, for example, the expression "seed material" can refer to -..-hole potatoes, cut potatoes, mini-tubers etc. In a preferred embodiment the method in accordance with the present invention involves the subjection of seed material to a temperature in the vicinity of 50°C and a pressure of the order of 200 lbs. per square inch, for a period of approximate!;/ 5 minutes. It sl-.ould be noted, however, that in practice the parameters involved in the method in accordance with the present invention will be varied to suit specific requirements, as for example variations in the size of the articles being treated, variations in the level of infection in the articles being treated etc. Indeed the temperature cf treatment, pressure of treatment and treatment time may be varied to suit such specific requirements. It should, be noted, however, that tests have shown that- treatment for any substantial period of time at temperatures above 55 C is responsible for too great a loss of plant life - the seeds will be effectively killed. Tests have also shown that the incidence of diseases such as powdery scab is substantial!:, ** reduced in less tem¬ perate climates, for example at temperatures below 20 C. It should furthermore be noted that experience has revealed the existence of an upper ceiling or limit to the pressure which can be applied to potatoes, for example. To be more specific, pressures in excess of 230 pounds per square inch have been fot to give rise tc cell rupture in potatoes and the like, thereby resulting in loss of plant life (as well as destruction of disease spores). In a further preferred embodiment the subjection of tainted material tc a pressure substantially less tl * an atmospheric may also have a marked effect on the degree of infection of the material being treated. In this regard it should be noted that the spores responsible for the disease known as powdery scab are in fact air-breathing, so to speak. It tlierefo e stands to reason that subjecting OMPI / . such spores to the effects of substantial Vacuum will result in the effective destruction of those spores. A further variation of the method in accordance with the present invention again involves the subjection 5 of seed material to elevated temperatures (less than 55 C) for a specified period, but this time at var in" pressure levels. 3y way of example, seed material could ust be subjected to a temperature of, say, 0°C for a certain period at a pressure of, for instance, 200 pounds per square 10 inch, the pressure then reduced to, say, 150 pounds per sπuare inch for a further period, and then ' returned to the original 200 pounds per square inch for an- additional period. Treatment such as this has been found to fracture, rather than rupture, -the spore balls without any catastrophic damage 15 to plant cells, thereby increasing the degree of penetration of any treating chemicals and hence increasing the suscept¬ ibility to chemical attack. In an especially preferred embodiment the method in accordance with the invention involves the treating of 20 tainted or infected seed material with appropriate chemicals at elevated temperatures and perhaps varying pressures. Such a hot, pressurized chemical dipping process has ' ean found to result in an increase in the degree of suffusion of the disease-destructive treating chemicals into the material 25 being treated. Indeed it is suspected that such a procedure will result in "daughter" tubers or the like from treated seed material -themselves including therein chemical material of a level sufficient to prevent infecting micro-organisms remaining in previously infected soil from attacking such » » 30 "daughter" tubers or the like. In other words such so- called "daughter" tubers will exhibit a derree of resistance to the infection. Such a situation will allow for the re¬ planting of previously infected frowing areas with substan¬ tially untainted plant material without risking subsequent 35 infection of future generations of the growing crop 'oy micro-organisms residual in the soil. In the preferred u.-a~e for the method c the OMPI invention as described herein, that is the '" treatment cr control of "powdery scab" in potatoes, chemicals considered suitable for the afore-mentioned hot-pressurized dipping process include mercury, formalin, a mixture of mercury and formalin, alcohol, hypo-sodium hypo-chloride, Ridomil, Difolatan, Senlate, i hane 1-45, Pine Oil, Triuzin, 3U-F0S, CaptanA, Diclone, P..ovral, carbolic acid and/or hydrochloric acid. G-enerally speaking, however, such chemicals are rather expensive, hence the preferred metho involving the subjectio of plant material to elevated temperatures at elevated or reduced pressures in the absence of an;' additional chemical material. It should be borne in mind that, whilst the aforegoing description refers merely to the treatment of "powdery scab" in potatoes, the method in accordance with the present invention could be employed for the simultaneous treatment of, for example, potatoes as proofing against a varietj ** of skin complaints. An apparatus for carrying out the method in accordance with the invention may include a pressure vessel having means associated therewith for raising or reducing the temperature and/or pressure existing in the vessel to suit particular requirements. Such variation in internal temperature ana pressure of the vessel may be achieved in z r_y known manner. The actual size of the pressure vessel itself will of course be dependent on projected demand. Such an apparatus will also include means allowing for the introd¬ uction of treating chemicals thereinto. "Powdery scab" in particular, has ^ oee found to be susceptible to elevated temperatures. Preferably, in order to ensure uniformity of temperature with a pressure vessel, the vessel itself may be immersed - wholly or partially - in a suitable fluid, such as for example water, which may then be heated by any known means. As a further precaution against the formation of localiz d "hot spots" or "cool spots" WHO be provided for circulating the heated fluid. In the instance of chemicals in the form of a bath being included within the pressure vessel whereby to constitute a chemical dip for the articles to be treated, means may also be included for regular stirring of the che .icals whereby to ensure uniformity of the treatment. Finally, it should be understood that the afore¬ going description refers merely to preferred embodiments of or usage for the method and apparatus in accordance with the present invention, and that variations and modifications are possible without departing from the spirit and scope of the invention, the ambit of which is to be determined from the following claims.

Claims: CLAIMS 1 - ) - 1. A method for the treatment of plant seed material, said method involving the subjection of the plant seed material to elevated or reduced temperatures, at a pressure other than atmospheric. 2. The method as claimed in claim 1, wherein said plant material is potatoes. 3. The method as claimed in claim 1 or claim 2, wherein said treatment occurs in a temperature range of from 20°C to 55°C. 4. The met h od as claimed in airy one of claims 1 to 3, wherein said treatment takes place at pressures greater than atmospheric but less than 230 pounds per square inch. 5. The method as claimed in claims 1 to 3, wherein said treatment takes place in a substantial vacuum. β. The method as claimed in _. _y one of the preceding claims, wherein said method includes treatment of said seed materials with disease destroj'ing chemicals. 7. The method as claimed in any one of the preceding claims, including the subjection of the plant seed material to elevated temperatures and varying pressures for a specified period of time. CMΓI

Inventors: QUICK DOUGLAS W
Applicants: QUICK DOUGLAS W
Application year: 1981
Main classification: A01C1
IPC codes: A01C1