caramel compositions according to the present invention are particularly useful in the treatment of plants susceptible to infection by or previously infected with cucumber mosaic virus ( cmv ). thus , both treatment to inhibit the infection of plants by cmv virus and treatment to inhibit the multiplication of the virus in infected plants are contemplated by the present invention . treatment to inhibit other viruses and fungi is contemplated as well . the treatment of plants according to the invention may involve spraying a caramel composition on the leaves of plants , adding the composition to the water supply of the plants , or in the case of plants grown by tissue culture , adding the composition to the culture media . treatment of both monocotyledonous and dicotyledonous higher plants is contemplated . other aspects and advantages of the present invention will be appreciated upon consideration of the following detailed description of presently preferred embodiments thereof . caramel compositions were tested for their ability to inhibit the infection of dicotyledonous vigna ungiculata subspecies sesquipedalis plants by cmv . cmv is rna virus transmitted mainly by aphids , which causes serious disease in a wide variety of crops including , for example , tomato , cucumber , zucchini , muskmelon , sweet potato , sugar beet and tobacco . the virus is carried by perennial ornamental plants such as the violet and the gladiolus . cmv is a plant virus of worldwide economic significance . a composition of 10 μg / ml caramel ( tb amano jitsugyo company ) in 0 . 1m phosphate buffer ph 7 . 0 was prepared . a small calligraphy brush was used to apply a coat of the caramel composition to a first leaf of two - leaf vigna unguiculata seedlings ( takii seed company , kyoto , japan ), either two hours before infection of the seedlings with cmv [ strain pepo obtained from the college of agriculture , university of osaka prefecture , osaka , japan , and described in annals of the phytopathological society of japan , 44 , 619 - 625 ( 1978 )], contemporaneously to infection , or two hours after infection . control seedlings were either totally untreated or treated only with 0 . 1m phosphate buffer ph 7 . 0 on a first leaf . the composition was applied to the front of the leaf of some seedlings and the back of the leaf of others . the second leaf of both the treated and control seedlings was not treated with the caramel composition or with buffer . the front of both leaves of both the treated and control seedlings was then infected with cmv by a method similar to that described in kopp et al ., supra . leaves were inoculated with virus by abrasion of the leaf surface in the presence of a suspension containing purified cmv . the infected seedlings were cultivated in a controlled environment at 25 ° c . for 3 days to allow the infection to develop . the number of infectious spots , equivalent to viral plaques , was then counted for each leaf of each seedling . the results of the assay are presented below in table 1 , wherein each number of infectious spots for treated and untreated leaves represents the average of the numbers of infectious spots obtained for ten seedlings . totally untreated control seedlings displayed more than 250 infectious spots per leaf . table 1__________________________________________________________________________ # of infectious spotsconcentration ( ug / ml ) treatment in relation side of leaves treated / untreatedof caramel in buffer to time of infection treated leaves leaves__________________________________________________________________________10 ≧ 2 hours before front 8 29 0 ≧ 2 hours before front 283 29910 ≧ 2 hours before back 32 71 0 ≧ 2 hours before back 173 18710 concurrent front 49 81 0 concurrent front 217 23810 concurrent back 28 28 0 concurrent back 164 18710 ≧ 2 hours after front 20 50 0 ≧ 2 hours after front 194 19810 ≧ 2 hours after back 50 56 0 ≧ 2 hours after back 248 231__________________________________________________________________________ the results presented in table 1 indicate that caramel compositions of the present invention inhibit the infectivity / multiplication of cmv . significantly , the protection afforded the plants by the compositions is systemic , as is evidenced by the reduced number of infectious spots on the untreated second leaf of the seedlings wherein the first leaf was caramel - treated . also highly significant was the fact that protection was also afforded the plants that were treated with the caramel compositions after infection with cmv . no damage to the caramel - treated leaves / plants was noted in comparison to the buffer - treated leaves / plants . in a collateral experiment , some adverse effects on seedling growth were noted when a caramel concentration of 100 μg / ml was employed . these results , along with the fact that caramel is already a commercial product produced on a large scale that meets food and drug regulations , indicate that the caramel compositions of the present invention satisfy the criteria for anti - pathogenic compositions likely to be successful in preventing or controlling the viral infection of plants . while the present invention has been described in terms of preferred embodiments , it is understood that numerous modifications and variations will occur to those skilled in the art . for example , compositions according to the invention may be effective against viruses other than cmv including tobacco mosaic virus and zucchini yellow virus , and may protect plants other than vigna unguiculata seedlings including tomato , cucumber and tobacco plants . the compositions may comprise diluents such as water and liquid fertilizer , and may be combined with other agents having anti - plant pathogen activity .
disclosed are compositions comprising caramel that have anti - plant pathogen activity . methods of treatment of higher plants with the compositions to inhibit both the infection of plants by pathogens and the multiplication of pathogens in infected plants are also provided . compositions according to the present invention are particularly suited for use against plant viruses such as cucumber mosaic virus .