FAMILY CHLOROGEXACEAE 



1155 



1. Aureogenus vastans (Holmes) 

 Black. {Mannor vastans Holmes, 

 Handb. Phytopath. Viruses, 1939, 94; 

 Black, Proc. Am. Philos. Soc, 88, 1944, 

 141.) From Latin vastare, to devastate. 



Common name : Potato yellow-dwarf 

 virus. 



Hosts: SOLAN ACE AE—Solanum tu- 

 berosum L., potato. COMPOSITAE— 

 Chrysanthemum leucanthemum L., var. 

 ■pinnatifidum Lecoq and Lamotte, daisy; 

 Rudheckia hirta L., black-eyed Susan. 

 CRUCIFERAE—Barbarea vulgaris R. 

 Br., common winter cress. LEGU- 

 MINOSAE — Trifolium pratense L., red 

 clover. Experimentally to numerous 

 species in these and other families. 



Geographical distribution: Northeast- 

 ern United States and southeastern 

 Canada. 



Induced disease : In potato, yellowing 

 of leaves, necrosis of stem, dwarfing of 

 plant; the stem, if split, shows rusty 

 specks especially at nodes and apex ; the 

 apex dies early; tubers are few, small, 

 close to the stem, often cracked, with 

 flesh discolored by scattered brown 

 specks; seed tubers tend to remain un- 

 rotted in the ground, becoming hard and 

 glassy ; some of them do not germinate in 

 warm soil, others produce shoots that die 

 before reaching the surface, giving poor 

 stands. In Chrysanthemum leucanthe- 

 mum var. pinnatifidum, at first, clearing 

 of veins; later, young leaves distorted, 

 thick, stiff, small; petioles short, leaves 

 erect, forming a rosette at the crown of 

 the plant ; with passing of the early 

 phases of the disease, foliage tends to 

 appear nearly normal, but remains darker 

 green and more erect than that of healthy 

 plants; virus is recoverable both during 

 and after the period of obvious disease 

 and infected plants may constitute an 

 important reservoir. In Trifolium in- 

 carnatum L., crimson clover, experiment- 

 ally, clearing of veins and yellowing of 

 younger leaves (in summer the yellowing 

 is usually replaced in part by an inter- 



veinal reddish-brown color on both leaf 

 surfaces extending from the margins in- 

 wards); dwarfing of entire plant; death 

 or a chronic disease characterized by 

 milder manifestations without, however, 

 vein enlargement or cupping of leaves. 

 In Nicotiana rustica L., experimentally, 

 yellowish primary lesions followed by 

 clearing of veins and systemic chlorosis; 

 the primary lesions facilitate quantitative 

 estimation of concentrations of this virus. 



Transmission : By inoculation of ex- 

 pressed juice, in the presence of finely 

 powdered carborundum, to Nicotiana 

 rustica; mechanical transmission very 

 difficult in other hosts tested. By graft- 

 ing. By clover leafhopper, Aceratagallia 

 sanguinolenta (Provancher) ; experiment- 

 ally, by other closely related leafhoppers, 

 Aceratagallia lyrata (Baker), A. obscura 

 Oman, and A. curvata Oman; not (for the 

 type variety of the virus) by Agallia con- 

 stricta Van Duzee ; very rarely by Agallia 

 quadripunctata (Provancher) and Agal- 

 liopsis novella (Say) (CICADELLI- 

 DAE). The vector Aceratagallia san- 

 guinolenta remains infective as an over- 

 wintering adult ; incubation period not 

 less than 6 days, commonly much longer; 

 virus does not pass to progeny of virulif- 

 erous leafhoppers through eggs or sperm; 

 this leafhopper varies genetically in 

 ability to transmit. 



Immunological relationships : No pro- 

 tection is afforded against necrotic effects 

 of a testing strain of this virus (var. 

 lethale Black) by prior inoculation of 

 Nicotiana rustica with isolates of Marmor 

 medicaginis, M. cucumeris, M. upsilon, 

 Annulus tabaci, A. orae, or A. dubius, 

 but the varieties vulgare Black and agal- 

 liae Black protect ; these specifically pro- 

 tecting strains give no similar protection 

 against formation of necrotic lesions by 

 subsequently applied isolates of Marmor 

 tabaci, M. lethale, Annulus tabaci, or A. 

 orae. 



Thermal inactivation : At 50 to 52° C in 

 10 minutes. 



