FAMILY MARMORACEAE 



1167 



2. Marmor constans McKinney. 

 (Jour. Washington Acad. Sci., 34, 1044, 

 326.) From Latin constans, fixed. 



Common name : Tobacco niild dark- 

 green mosaic virus. 



Hosts : SOLA NACEAE—Nicotiana 

 glauca R. Grah., tree tobacco. 



Insusceptible species: SOLAN A- 

 CEAE — Lycopersicon esculentum Mill., 

 tomato. CUCURBITACEAE— 



Cucumis sativus L., cucumber. 



Geographical distribution : Islands of 

 Grand Canary and Teneriffe. 



Induced disease : In Nicotiana glauca, 

 sj'stemic chlorotic mottling. 



Transmission : By inoculation of ex- 

 pressed juice. No insect vector is 

 known. 



Thermal inactivation: At about 86°C. 

 in 10 minutes. 



Literature : McKinney, Jour. Agr. 

 Res., 39, 1929, 557-578; Am. Jour. 

 Bot., 28, 1941, 770-778; Peterson and 

 McKinney, Phytopath., 28, 1938, 329- 

 342; Thornberry and McKinney, ibid., 

 29, 1939, 250-260. 



3. Manner astrictum Holmes. 

 (Holmes, Handb. Phytopath. Viruses, 

 1939, 27; Musivum astrictum Valleau, 

 Phytopath., SO, 1940, 823.) From Latin 

 astrictus, limited, in reference to host 

 range. 



Common names : Cucurbit-mosaic 

 virus, English cucumber-mosaic virus. 



Hosts: CUCURB IT ACE AE— Cucu- 

 mis sativ2(s L., cucumber; C. anguria L., 

 gherkin ; C. melo L., melon ; Citrullus vul- 

 garis Schrad., watermelon; only cucur- 

 bitaceous plants have appeared to be 

 susceptible thus far. 



Insusceptible species : All tested sol- 

 anaceous species. CUCURBITA- 

 CEAE — Bryonia dioica L.; Cucurhita 

 pepo L., vegetable marrow. LEGU- 

 MINOSAE — Phaseolus vulgaris L. var. 

 Golden Cluster. 



Geographical distribution : England. 



Induced disease : In cucumber, clearing 

 of veins and crumpling in young leaves, 

 followed by a green-mosaic mottling, with 



blistering and distortion of newly formed 

 leaves. Plant stunted. Fruit un- 

 marked or slightly mottled. Diseased 

 plants less obviously affected during win- 

 ter months. 



Transmission : By inoculation of ex- 

 pressed juice. No insect vector is 

 known . 



Serological relationships : Weak cross 

 precipitin reactions and full cross-neu- 

 tralization reactions with tobacco -mosaic 

 virus (Marmor tabaci). Two common 

 antigens postulated. Preparations of vi- 

 rus that have been inactivated by treat- 

 ment with nitrous acid or X-raj^s are still 

 antigenic. 



Thermal inactivation : At 80 to 90° C in 

 10 minutes. 



Filterability : Passes Pasteur-Cham- 

 berland filters Lj to L?, and membranes 

 of 150 millimicrons average pore diameter. 



Other properties : Virus, infectious in 

 dilution of 10"^°, is present to the extent 

 of 0.2 to 0.3 gram per liter of juice from 

 diseased plants. Preparations show 

 sheen and anisotropy of flow, indicating 

 rod-shaped particles. Solutions stronger 

 than 2.5 per cent separate into 2 layers at 

 room temperature, the lower being the 

 more concentrated and birefringent. 

 Precipitates with ammonium sulfate show 

 needle-shaped paracrystals. Sedimenta- 

 tion constants Sjo" = 173 X lO'i^ cm. 

 sec.~J dyne~^ and about 200 X 10"!^ cm. 

 sec.~i dyne~i. Virus withstands drying 

 without inactivation but with partial loss 

 of ability to show anisotropy of flow and 

 with reduction of serological activity to 

 about half. Tryptophane content 1.4 

 per cent, phenylalanine 10.2 per cent, 

 the first lower and the second higher than 

 in tobacco-mosaic virus. 



Literature: Ainsworth, Ann. Appl. 

 Biol., 22, 1935, 55-67; Bawden and Pirie, 

 Nature, 139, 1937, 546-547; Brit. Jour. 

 Exp. Path., 18, 1937, 275-291; Knight, 

 Arch. Virusf., 2, 1942, 260-267; Knight 

 and Stanley, Jour. Biol. Chem., I4I, 1941, 

 29-38; 141, 1941, 39-49; Price, Am. Jour. 

 Bot., 27, 1940, 530-541; Price and Wyc- 

 koff, Nature, 14I, 1938, 685. 



