FAMILY CHLOROGENACEAE 



1147 



mally dormant buds to adventitious 

 growth and abnormally erect habit are 

 the most constant features. Chlorosis is 

 absent or inconspicuous in some hosts. 



Transmission : By leafhopper, Macro- 

 steles divisus (Uhl.) (= Cicadiila sex- 

 notata (Fall.), C. divisa (Uhl.)) {CICA- 

 DELLIDAE). Incubation period, 

 about 2 weeks . Some strains of this virus 

 are transmitted also by the leafhoppers 

 Thamnotettix montanus Van D. and T. 

 geminatiis Van D. (CICADELLIDAE). 

 By grafting. By dodder. Not through 

 seeds of diseased plants. Not by me- 

 chanical inoculation of plants, but virus 

 has been passed from insect to insect 

 mechanically in Macrosteles divisus; juice 

 from viruliferous insects contains little 

 virus just after inoculation, but the effec- 

 tive concentration increases at least 

 100-fold between the 2nd and 12th day 

 of a 17-day incubation period; it seems 

 greatest before the insects begin to infect 

 the aster plants on which they are main- 

 tained. 



Thermal inactivation : In juice from 

 viruliferous insects, at about 40° C in 10 

 minutes; at 25° C in 2 to 3 hours. In 

 plant tissues, at 38° to 42° C, in 2 to 3 

 weeks; cured plants fully susceptible to 

 reinfection. In insect vector, M. divisus, 

 at 31° C in 12 days. 



Other properties : Virus in juices de- 

 rived from insects is more stable at 0° C 

 than at 25° C or when frozen ; at 0° C it 

 withstands storage 24, not 48, hours in 0.85 

 per cent NaCl solution at pH 7.0 but most 

 of the virus is inactivated in this time ; it 

 withstands dilution 1:1000 in neutral 

 0.85 per cent NaCl solution; for brief 

 (less than 5-minute) exposures, it re- 

 mains viable over the range from pH 5 

 to 9. 



Literature: Black, Phytopath., SI, 

 1941, 120-135; 83, 1943, 2 (Abst.) ; John- 

 son, ibid., 31, 1941, 649-656; Kunkel, Am. 

 Jour. Bot., 13, 1926, 646-705; Contrib. 

 Boyce Thompson Inst., 3, 1931, 85-123; 

 4, 1932, 405-414; Am. Jour. Bot., 2^, 

 1937, 316-327; 28, 1941, 761-769; Linn, 

 Cornell Agr. Exp. Sta. (Ithaca), Bull. 



742, 1940; Ogilvie, Bermuda Dept. Agr., 

 Agr. Bull. 6, 1927, 7-8 ; Severin, Hilgardia, 

 3, 1929, 543-583; Phytopath., 20, 1930, 

 920-921; Hilgardia, 7, 1932, 163-179; 8, 

 1934, 305-325, 339-361; Phytopath., 30, 

 1940, 1049-1051 ; Hilgardia, 14, 1942, 411- 

 440; Severin and Haasis, Hilgardia, 8, 

 1934, 329-335. 



Strains : Two variant strains, one found 

 in nature, the other derived experiment- 

 ally, have been given varietal names to 

 distinguish them from the type variety, 

 vulgaris H. {loc. cit., 2) : 



la. Chlorogenus callistephi var. califor- 

 nicus H. {loc. cit., 3). From California, 

 name of state in which this strain was first 

 recognized. Common name: Celery-yel- 

 lows strain of aster-yellows virus. Dif- 

 fering from the type variety by ability to 

 infect celery {Apium gravcolens L. — 

 UMBELLIFERAE) and zinnia {Zinnia 

 elegans Jacq.— COMPOS IT AE) (Kun- 

 kel, Contrib. Boyce Thompson Inst., 4, 

 1932, 405-414; Severin, Hilgardia, 3, 1929, 

 543-583; 8, 1934,305-325). 



lb. Chlorogenus callistephi var. ai- 

 tenuatus H. {loc. cit., 4). From Latin 

 attenuatus, weakened. Common name: 

 Heat -attenuated strain of aster-yellows 

 virus. Differing from the type variety 

 by inducing less severe chlorosis and less 

 uprightness of new growth in affected as- 

 ter plants (Kunkel, Am. Jour. Bot., 2^, 

 1937,316-327). 



2. Chlorogenus australiensis comb, 

 nov. From Australia, name of continent. 

 Synonym: Galla australiensis H. {loc. 

 cit., 107). 



Common names : Tomato big-bud virus ; 

 virescence virus; perhaps also stowboor 

 virus, tobacco stolbur or montar virus, 

 eggplant little-leaf virus. 



Hosts: SOLA N ACE AE— -Datura stra- 

 vioniiim L., Jimson weed; Lycopersicon 

 esculentum Mill., tomato ; Nicotiana taba- 

 curn L., tobacco; Solaman melongena L., 

 eggplant ; S. nigrum L., black nightshade. 

 Recently a long list of species in this and 



