FAMILY CHLOROGENACEAE 



1159 



Transmission : By leafhopper, Cicadula 

 himacidata Evans (CICADELLIDAE). 



Literature: Schindler, Jour. Austral. 

 Inst. Agr. Sci., 8, 1942, 35-37. 



Genus VI. Fractilinea McKinney. 



(Jour. Washington Acad. Sci., 34, 1944, 148.) 



Viruses of the Stripe-Disease Group ; hosts grasses ; insect vectors, cicadellid and 

 fulgorid leafhoppers. Generic name from Latin, meaning interrupted and line. 

 Tlie type species is Fractilinea maidis (Holmes) McKinney. 



Key to the species of genus Fractilinea. 



I. Vectors, cicadellid leafhoppers. 



1. Fractilinea maidis. 



2. Fractilinea oryzae. 



3. Fractilinea tritici. 



4. Fractilinea quarta. 



II. Vectors, fulgorid leafhoppers. 



5. Fractilinea zeae. 



6. Fractilinea avcnae. 



1. Fractilinea maidis (Holmes) Mc- 

 Kinney. {M armor maidis Holmes, 

 Handb. Phytopath. Viruses, 1939, 56; 

 Fractilinea maidis JMcKinney, Jour. 

 Washington Acad. Sci., 34, 1944, 149.) 

 From New Latin mays, corn (i.e. maize). 



Common name: Maize-streak virus. 



Hosts: GRAMINEAE—Zea mays L., 

 corn (maize); Digitaria horizontalis 

 Willd., Eleusine indica Gaert.; Sac- 

 charum officinarum L., sugar cane. 



Geographical distribution : Africa. 



Induced disease : In corn, pale spots at 

 base of young leaf, followed by chlorotic 

 spotting and streaking of subsequently 

 formed leaves. Virus moves rapidly (up 

 to 40 cm in 2 hours at 30° C) after intro- 

 duction into host plant by insect. More 

 virus in chlorotic spots than in green areas 

 of affected leaves. 



Transmission : B3' leafhoppers, Cica- 

 dulina (= Balclutha) mbila (Naude), C. 

 zeae China, and C. storeyi China (CICA- 

 DELLIDAE). In C. mbila ability to 

 transmit this virus is controlled by a 

 sex-linked dominant gene ; active male 

 (AX) (Y), inactive male (aX) (Y), inac- 

 tive female (aX) (aX), active female 

 (AX) (AX) or (AX) (aX). Inactive in- 

 dividuals ingest virus when feeding, but 

 can become infective only if the intestine 



is wounded purposely or accidentally. 

 If inoculated artificially by introducing 

 virus into blood, both active and inactive 

 insects become infective. Incubation 

 period, 6 to 12 hours at 30° C. Young not 

 infected through the egg. Infective leaf- 

 hopper cannot transmit virus unless feed- 

 ing puncture exceeds a minimum period, 

 about 5 minutes in duration. This virus 

 has not been transmitted to its plant 

 hosts by inoculation of expressed juices. 



Filterability : At pH 6, passes Cham- 

 berland Li and L3, Berkefeld V and N, 

 filters; retained by Seitz E K filter disc. 



Literature: Storey, Ann. Appl. Biol., 

 12, 1925, 422-439; 75, 1928, 1-25; 19, 1932, 

 1-5; Proc. Roy. Soc, B, 112, 1932, 46-60; 

 113, 1933, 463-185; 125, 1938, 455-477; 

 Ann. Appl. Biol., 21, 1934, 588-589; 24, 

 1937, 87-94; East Afr. Agr. Jour., 1, 1936, 

 471-475 ; Storey and McClean, Ann. Appl. 

 Biol., 17, 1930, 691-719. 



Strains : Two strains that differ radi- 

 cally from the type, var. typicum H. 

 {loc. cit., 56), have been given varietal 

 names, as follows : 



la. Fractilinea maidis var. sacchari H. 

 (loc. cit., 57). From New Latin Sac- 

 charum, generic name of sugar cane. 

 Common name : Cane -streak strain of 



