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MANUAL OF DETERMINATIVE BACTERIOLOGY 



VI, Stripe-Disease Group. Viruses inducing diseases characterized by chlorotic 

 striping; hosts grasses. Vectors, cicadellid and fulgorid leafhoppers. 

 Genus VI. Fractilinea, p. 1159. 



Genus I. Chlorogenus Holmes. 

 {Loc. cit., 1.) 



Viruses of the Typical Yellows Group, inducing diseases usually characterized by 

 stimulation of normally dormant and adventitious buds to produce numerous slender 

 shoots with long internodes, by chlorosis without spotting, or by both growth of nu- 

 merous slender shoots and chlorosis. Invaded parts abnormally erect in habit. Af- 

 fected flowers often virescent. Hosts, dicotyledonous plants. Vectors, so far as 

 known, exclusively cicadellid leafhoppers. Generic name from Greek chloros, light 

 green or yellow, and suffix, gen, signifying producing, from Greek genos, descent. 



The type species is Chlorogenus callistephi Holmes. 



Key to the species of genus Chlorogenus. 

 I. Natural hosts many, in various families of plants. 



1. Chlorogenus callistephi. 



2. Chlorogenus australiensis. 



II. Known natural hosts relatively few. 



A. Natural hosts rosaceous. 



B. Natural hosts solanaceous. 



C. Natural host sandal. 



D. Natural host cranberry. 



E. Natural host locust. 



F. Natural host alfalfa. 



G. Natural host hop. 



1. Chlorogenus callistephi Holmes. 

 (Handb. Phytopath. Viruses, 1939, 2.) 

 From New Latin Callistephiis, generic 

 name of the China aster. 



Common names: Aster-yellows virus, 

 lettuce white-heart virus, Erigeron-ycl- 

 lows virus. 



Hosts : Callistephus chinensis Nees, the 

 China aster, is the host that has been 

 studied most. 170 or more species in 38 

 different families of dicotyledonous 

 plants have been shown susceptible. 

 Lettuce, endive, carrot, buckwheat, pars- 

 nip, and New Zealand spinach are among 

 the hosts of economic importance. 



3. Chlorogenus persicae. 



4. Chlorogenus solani. 



5. Chlorogenus santali. 



6. Chlorogenus vaccinii. 



7. Chlorogenus robiniae. 



8. Chlorogenus medicaginis. 



9. Chlorogenus humuli. 



Insusceptible species : All tested spe- 

 cies of the family Leguminosae and some 

 species of all other tested families have 

 appeared naturally immune. 



Geographical distribution: U. S., Can- 

 ada, Bermuda, Japan, and Hungary. In 

 California the celery-yellows strain of 

 this virus replaces the type. 



Induced disease : In most host species 

 the characteristics of disease are clearing 

 of veins, followed by chlorosis of newly 

 formed tissues, stimulation of normally 

 dormant buds to growth, malformation, 

 virescence of flowers, sterility, and up- 

 right growth habit. Stimulation of nor 



