1148 



MANUAL OF DETERMINATIVE BACTERIOLOGY 



other families have been reported as sus- 

 ceptible to virescence virus, presumed to 

 be an isolate of tomato big-bud virus. 

 (Hill, Jour. Counc. Sci. Ind. Res., 16, 

 1943, 85-92). 



Geographical distribution : Australia, 

 especially New South Wales; viruses 

 causing somewhat similar diseases have 

 been reported also from the Crimea and 

 the northwestern United States. 



Induced disease: In tomato, flowers 

 erect, virescent, calyx bladder-like, pol- 

 len sterile; floral proliferation. Growth 

 of axillary shoots stimulated. New 

 leaves progressively smaller. Youngest 

 leaves yellowish-green in color, especially 

 at their margins ; usually purplish under- 

 neath. Hypertrophy of inner phloem. 

 No intracellular inclusions. Fruit red- 

 dens imperfectly and becomes tough and 

 woody. Roots appear normal. In So- 

 lanum nigrum, axillary shoots numerous, 

 leaves small, internal phloem adventi- 

 tious. In tobacco, plants dwarfed ; leaves 

 recurved, distorted, twisted, thickened, 

 brittle, yellowish green, hanging down 

 close to stem ; small leaves on shoots from 

 axillary buds; proliferation and vires- 

 cence of flowering parts ; chlorotic clear- 

 ing of veins as early effect of disease ; 

 upper surface of foliage appears glazed; 

 some necrosis of veins, in old leaves, near 

 tips and margins or on midrib; viable 

 seed rarely produced; calyx bladder-like, 

 floral axis may form short branches bear- 

 ing small leaves ; disease sometimes called 

 bunchy top. 



Transmission: By leafhopper, Tham- 

 notettix argentata Evans {CICADELLI- 

 DAE). Experimentally bj' budding and 

 other methods of grafting. Not by inocu- 

 lation of expressed juice. 



Literature : Cobb, Agr. Gaz. New South 

 Wales, 13, 1902, 410-414; Dana, Phyto- 

 path., 30, 1940, 866-869; Hill, Jour. Aus- 

 tral. Inst. Agr. Sci., 6, 1940, 199-200; 

 Jour. Council Sci. Ind. Res., 10, 1937, 

 309-312; 16, 1943, 85-92; Michailowa, 

 Phytopath., 25, 1935, 539-558; Rischkov 

 et al., Ztschr. Pflanzenkr., 43, 1933, 496- 



498; Samuel et al., Phytopath., 23, 1933, 

 641-653. 



3. Chlorogenus persicae H. (loc. cit., 

 5). From New Latin Persica, former 

 generic name of peach. 



Common names : Peach-yellows virus, 

 little-peach virus. 



Hosts : ROSACE AE — Prunus persica 

 (L.) Batsch, peach; P. salicina Lindl., 

 Japanese plum; and all other tested spe- 

 cies of the genus Prunus. 



Geographical distribution : Eastern 

 United States and Canada, south to 

 North Carolina. First occurred near 

 Philadelphia in this country. Origin 

 perhaps oriental ; introduction in oriental 

 plums suspected. Not in Europe. 



Induced disease : In peach, clearing of 

 veins, production of thin erect shoots 

 bearing small chlorotic leaves, followed 

 by death in a year or two . In early stages 

 of the disease there is premature ripening 

 of fruit. In Japanese plum, systemic in- 

 fection but no obvious symptoms. 



Transmission : By the leafhopper, Ma- 

 cropsis trimaculala (Fitch) {CICADEL- 

 LIDAE). By budding; virus spreads 

 down stem from point of bud insertion 

 faster than up. Not by inoculation of 

 expressed juice, despite numerous at- 

 tempts. Not by pollen of diseased trees. 



Immunological relationships : Presence 

 of peach-yellows virus immunizes tree 

 against little-peach virus, formerly con- 

 sidered an independent entity. 



Thermal inactivation : In peach tissues, 

 at 34° to 35° C in 4 to 5 days ; at 44° C in 

 30 minutes ; at 47° C in 10 minutes ; at 50° 

 C in 3 to 4 minutes ; at 56° C in 15 seconds. 



Other properties : Trees and bud sticks 

 may be treated safely with heat sufficient 

 to kill the virus. Cured trees are sus- 

 ceptible to reinfection. 



Literature : Blake, N. J. Agr. Exp. Sta., 

 Bull. 226, 1910; Kunkel, Contrib. Boyce 

 Thompson Inst., 5, 1933, 19-28; Phyto- 

 path., 26, 1936, 201-219, 809-830; 28, 1938, 

 491-497; Manns, Trans. Peninsula Hort. 

 Soc, 23, 1933, 17-19; Manns and Manns, 



