FAMILY MARMORACEAE 



1203 



Key to the species of genus Acrogenus 

 I. Infecting potato. 



II. Infecting black currant. 



1. Acrogenus solani Holmes. (Handb. 

 Phytopath. Viruses, 1939, HI.) From 

 New Latin Solanum, generic name of 

 potato. 



Common names : Potato spindle-tuber 

 virus, potato spindling-tuber virus, po- 

 tato marginal leaf -roll virus. 



Host: SOLAN AC EAE— Solanum tu- 

 berosum L., potato. 



Geographical distribution : United 

 States and Canada. 



Induced disease : Plants erect, stiff, 

 spindly, lacking vigor. Leaves small, 

 erect, darker green than normal. Peti- 

 oles sometimes slender, brittle. Tubers 

 long, cylindrical, irregular in shape, tap- 

 ered at ends, smooth and tender-skinned, 

 of softer than normal flesh in spring. 

 Eyes of tuber conspicuous. 



Transmission: By inoculation of ex- 

 pressed juice; by use of contaminated 

 knife in cutting successive tubers before 

 planting; by contacts of freshly cut seed 

 pieces. By aphids, Myzus persicae 

 (Sulz.) and Macrosiphum solanifolii 

 Ashm.i=M.geiKoch) (APHIDIDAE). 

 Also by certain leaf-eating insects. 



Thermal inactivation : At 60 to 65° C in 

 10 minutes (in tuber tissues). 



Literature : Bald et al., Phytopath., 31, 

 1941, 181-186; Folsom, Maine Agr. Exp. 

 Sta., Orono, Bull. 312, 1923; Goss, Phyto- 

 path., 16, 1926, 233, 299-303; 18, 1928, 

 445-448; Nebraska Agr. Exp. Sta., Res. 

 Bull. 47, 1930; 53, 1931; Jaczewski, La 

 Defense des Plantes, Leningrad, 4, 1927, 

 62-77 (Rev. Appl. Mycol., 6, 1927, 572- 

 573, Abst.) ; McLeod, Canad. Exp. Farms, 

 Div. Bot., Rpt. for 1926, 1927. 



1. Acrogenus solani. 



2. Acrogenus ribis. 



Strains : A strain causing unmottled 

 curly dwarf of potato has been given a 

 varietal name to distinguish it from the 

 type, var. vulgaris H. (loc. cit.. Ill) : 



la. Acrogenus solani var. severus H. 

 (loc. cit., 112). Inducing symptoms in 

 potato on the whole more severe than 

 those caused by the type strain. 



Common name : Unmottled curly-dwarf 

 strain of potato spindle -tuber virus. 

 (Goss, Nebraska Agr. Exp. Sta., Res. 

 Bull. 47, 1930; 53, 1931 ; Schultz and Fol- 

 som, Jour. Agr. Res., 25, 1923, 43-118.) 



2. Acrogenus ribis H. (loc. cit., 112). 

 From Latin ribes, currant. 



Common name : Black-currant rever- 

 sion-disease virus. 



Host: SAXIFRAGACEAE—Ribes 

 nigrum L., European black currant. 



Geographical distribution : British 

 Isles. 



Induced disease : In European black 

 currant, leaves abnormally narrow and 

 flat, small veins few. Flowers sometimes 

 nearly transparent, smooth, sepals 

 brightly colored beneath. Flowers and 

 small fruits fall. Stems less woody than 

 normal, with tendency to excessive gum 

 production. 



Transmission : By grafting. By big- 

 bud mite, Eriophyes ribis (ERIOPHYI- 

 DAE). Not by inoculation of expressed 

 juice. Not through soil. Not through 

 seeds from diseased plants. 



Literature : Amos and Hatton, Jour. 

 Pom. and Hort. Science, 6, 1926, 167-183; 

 Amos et al., in East Mailing Res. Sta., 

 15th Ann. Rpt., 1928, 43-46; Lee, Ann. 

 Appl. Biol., 9, 1935, 49-68. 



Genus III. Cerium Holmes. 

 {Loc. cit., 119.) 

 Viruses of the Leaf -Roll Group, inducing diseases usually characterized by thicken- 



