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4 > Image 4 of Kentucky farm and home science, vol. 3 No. 4 fall 1957

Part of Kentucky Agricultural Experiment Station

LONG-TERM WORK SHOWS DIFFICULTIES IN INTERPRETING 4.; m toms In Le umes t V` S Q II`llS y W. A,,.`~ Several different viruses can cause mosaic in red clover; .4. also a wide range of symptoms can be induced by in- _ oculation with a single culture - new By STEPHEN I)lA(IHUN and LAWRENCE HENSON ._ _ i:=v iii`` . o: > is izl I c F ` lied clover plants with symptoms of virus infection i '` Q _`-_= A _ are common in Kentucky, as well as in other Cl0V1` .:_Vy{ { V= .`_: > growing areas of the United States. The appearance nni rf of infected plants is variable. Most commonly dis- i`' , ==_v ___l: ;-_ eased plants show either yellowing of veins or yellow ': _ 2 V .' iv K speckling of the leaflets; the latter is called mosaic or ,r :i ..; I _;__ i lii l _,. mottle. Mosaic may be mild in some plants, moderate M 2 ,,{, "`i' L ' r` in others, and severe in still others. ln a relatively ;_V __ Al , -.< 17*8-1**- { ` few plants veins and petioles become dead and black. ii` i Q . L y and leaflets become twisted. In some cases the dying . ` Y ; ___; 2 l ` l U1` l|Cl'0SlS Spwzltls into the buds, and eventually the Q ~ i I aa y entire plant dies. A high percentage of plants showing ___; _, ;__ __,, _,.i . V . `,..__ _ $}H1pf0lnS is found in some field; UVVI I fi >f Purpose of Experiments __'=:; gt __; ` F. lu july 1952 experiments, which are continuing, ``i_` i **.* were started by the Kentucky Agricultural Experi- H; ment Station to determine what virus or viruses cause S, A" `A`} y .-_ " the symptoms in red clover; and also to determine _ i g ;,. i whether the wide range of symptoms present in clover Fig` lb` ga- fields is caused by a mixture of viruses, or by strains These figures sh ow ._,_ ?~$i` of one virus, or by different reactions to a single virus $Ymlm$ ef the }'l rr i` ____ _:. .. of plants in a genetically variable population that low b" '""l" i lg make up a variety of red clover. red (llovcli = 'l`he purpose of this article is to emphasize the dif- O M IM A V liculties involved in identifying virus diseases of forage viruses because viruses themselves are so tiny that a_ s legumes and to report the results of some of the work they cannot be seen with the highest powers of the pi being done with ied clover viruses at the Kentucky ordinary light microscope, and are identified only in- Station. directly on the basis of their properties and behavior. , _ ' lt is almost impossible to identify virus diseases of Partly because of these difficulties, sufficient attention red clover on the basis of field symptoms alone because has not been given to a study of virus diseases of red * i symptoms caused by a number of viruses may be very clover anywhere; consequently, specific detailed in- MA similar. Several viruses can cause mosaic in red clover; formation about virus diseases of red clover is not ` e among them aie the pea mosaic virus. yellow bean available. For that matter there is not yet general i mosaic virus. alfalfa mosaic virus, red clover vein agreement among plant pathologists as to what the a` mosaic virus. pea streak virus, potato yellow dwarf most connnon virus in red clover actually is. virus. and cncuinber mosaic virus. Even with the use To identify viruses accurately it is necessary to know ** ` of laboratory facilities it is difficult to identify these something about the host range, kinds of symptoms. ,,___ 4 l{l]N'l`ll(ZKY Fanxi Asn lfoxu; St;ii;x<:i:F..i.i. 1957 ai 4 s{