FAMILY MARMORACEAE 



1181 



Infective in dilutions to 10~'. By aphids, 

 Macrosiphum pisi Kalt. and M. solani- 

 folii Ashm. (= M. gei Koch) {APHI- 

 DIDAE), with incubation periods of 

 about 12 hours before the insects can 

 infect. Xot through seeds from diseased 

 plants. 



Thermal inactivation : At 66° C in 10 

 minutes. 



Literature : Boning, Forsch. Geb. Pflan- 

 zenkr. u. Immun. Pflanzenreich, J^, 1927, 

 43-111; Johnson and Jones, Jour. Agr. 

 Res., 54, 1937, 629-638; Loring et al., 

 Proc. Soc. Exp. Biol, and Med., 38, 1938, 

 239-241; Osborn, Phytopath., 25, 1935, 

 160-177 ; 28, 1938, 749-754, 923-934 ; Pierce , 

 Jour. Agr. Res., 51, 1935, 1017-1039; 

 Snyder, Phytopath., 24, 1934, 78-80; 

 Stubbs, ihid., 27, 1937, 242-266. 



21. Marmor medicaginis H. {loc. cil., 

 91). From New Latin Medicago, generic 

 name of alfalfa (lucerne). 



Comnion name : Alfalfa-mosaic virus. 



Hosts : LEG UMINOSA E— Medicago 

 sativa L., alfalfa (lucerne). SOLAN A- 

 CEAE — Solanum tuberosum L., potato. 

 Experimentally, also transmissible to 

 many species of dicotyledonous plants 

 (summarized by Price, Am. Jour. Bot., 

 27, 1940, 530-541) including CL^CL' 7?^/- 

 TACEAE — Cucumis sativus L., cucum- 

 ber. COM POS I T AE— Zinnia elegans 

 Jacq., zinnia. LEGUMINOSAE— 

 Phaseolus vulgaris L., bean; Trifolium 

 incarnaium L., crimson clover. SOL- 

 ANACEAE — Capsicum frutescens L., 

 pepper; Lycopersicon esculentum ]\Iill., 

 tomato; Nicotiana tabacum L., tobacco. 



Geographical distribution : United 

 States. 



Induced disease : In alfalfa, systemic 

 chlorotic mottling, tending to be masked 

 at times. In bean, (most varieties) 

 small necrotic primary lesions, reddish 

 brown at periphery. No secondary le- 

 sions. Some bean varieties show no 

 lesions after inoculation; one of these, 

 Refugee Rogue, possesses two dominant 

 genes either of which will confer this type 

 jf resistance. In tobacco, white necrotic 



flecks, small rings and arcs on inoculated 

 leaves ; later, systemic mottling, followed 

 by production of necrotic oak-leaf pat- 

 terns ; virus content may be low in plants 

 long diseased, especially in summer. 



Transmission : Bj^ inoculation of ex- 

 pressed juice. By aphids, Macrosiphum 

 pisi Kalt. (for typical strain) and M. 

 solanifolii Ashm. (for potato-calico 

 strain) (APHIDIDAE). Not through 

 seeds from diseased plants. 



Immunological relationships : Resis- 

 tance to superinfection with the type of 

 this virus is conferred by earlier infection 

 with potato-calico virus (now considered 

 a related strain but earlier regarded as 

 distinct), but not by earlier infection 

 with potato-mottle virus, cucumber- 

 mosaic virus, or the Canada-streak strain 

 of potato aucuba-mosaic virus. 



Thermal inactivation : At 65 to 70° C in 

 10 minutes. 



Other properties : Sedimentation con- 

 stant, 73.9 ± 5.2 X 10-13 cm. per sec. 

 in a unit centrifugal field. Specific 

 volume 0.673. Particles spherical or 

 nearly so. Diameter 16.5 millimicrons; 

 weight 2.1 X 10^ times hydrogen unit. 

 Isoelectric point about pH 4.6. Inacti- 

 vated and, more slowly, hydrolyzed by 

 trypsin. 



Literature : Black and Price, Phyto- 

 path., 30, 1940, 444-447 ; Lauffer and Ross, 

 Jour. Am. Chem. Soc, 62, 1940, 3296-3300, 

 Pierce, Phj^topath., 24, 1934, 87-115; 

 Price, Am. Jour. Bot., 27, 1940, 530-541; 

 Ross, Phytopath., 31, 1941, 394-410, 410- 

 420; Wade and Zaumeyer, Jour. Am. Soc. 

 Agron., 32, 1940, 127-134; Zaumeyer, 

 Jour. Agr. Res., 56, 1938, 747-772. 



Strains : At least one strain of alfalfa- 

 mosaic virus was formerly considered as 

 an independent virus, causing a disease 

 known as calico in potato. It has now 

 been given varietal rank and distin- 

 guished from the type, var. typicum 

 Black and Price (Phj^topath., 30, 1940, 

 446) by the following name : 



21a. Marmor medicaginis var. solani 

 Black and Price (Phytopath., 30, 1940, 



