Resistant Clover Clones from leaf marking that is common on red clover.`The _
(cmltinucd from Page 3) absence of leaf marking serves as an aid in identifying ‘ ·
the clones. _ .
  . Results of tests under greenhouse and field con- ,
  ditions show that in clones KyC6 and KyC71-8 the “
  virus commonly invades the plants systemically and PQ ‘
    ( usually kills them, but in clones KyC40, KyC4()-1 and
  ° KyC40-2 the virus tends to remain confined in the __ '
  local lesions (Fig. 2). These three clones are vigorous, __
      of good appearance, without leaf markings, and re- ,  
f‘,° J       ,·v‘ ' tiif Q   =l_   yvvg     1; p'  sistant to at least some isolates of bean yellow mosaic , 4
  .V ,V q      ; v1rus.'They seem to have considerable promise as  
.   . { {   breeding stock for development of a variety of red _.‘
      AAVA ;;. _,v· lat. _) A p clover resistant to this common virus disease of red ‘··»
· .7 ;     · " clover m Kentucky.
      A B e s i d e s helping develop resistant varieties, is
Fig. 2.—These dead spots (necrotic lesions) on a leaf of a there is a Second and perhaps equaux practical hse Y
plant of clone Ky(Z7l-8 remained localized and did not for ii€Ci`OtiC`SPOttihg PiahtS> namely. tot Comparing T
spread. The leaf had been rubbed with bean yellow the relative effectiveness of two or more preparations W.
mosaic virus. of the virus. After a necrotic-spotting leaf is rubbed { . 
because in some of them the virus becomes localized With virus, the virus €ht€i's the C€iis» ihuitiPii€s» tihti I
or immobilized in the small necrotic spots and fails kills it gi`0uP of cells. Causihg a visible dead sPOt· Oh'
to spreatl into the growing parts of the plant. In such Vi0usiY this tuihishes si ihsiihs thi Chuhtihg the with
cases the result is a paradoxical situation in which tive huihhei Ot active Viius Piiiticies ih ths Pi€Pattt‘
practical resistance is based on a reaction that is really tioii with which th€ isai Was rubbed. ahd ttii C0ihPth" » , I
one of extreme susceptibility or sensitivity, as a nec- ihg Ohh Pispaiatiuh with ahuthsh BY the hss of h€'s‘ , QA 
,·(,tic-SP(,ttmg reucmm iS_ rotic-spotting clones we have learned how to prepare I _
This type of necrotic-spotting resistance has been iihti use ihhcuiuih mote €tt€CtiV€iY than W6 Chhiti do L .
exploited successfully by plant pathologists in develop- h€iOi€· This khowiedgs is tissthi ih the sstitch tht i`€‘ r
ing virus-resistant varieties of plants. For example, the sistiiht Phihts- Whhh ihtihY Piahts must be shhlhcthti V
hurlcy mbucco mosuicqcsismnt varieties Ky35’ Ky57’ to the disease by inoculation. It is also useful and im- "‘
and Ky58 developed by plant pathologists at the Ken- Phitttht ih stutiYihg the ihhsiittihcs Ot t€sisttihC€·
tucky Agricultural Experiment Station carry the nec- -
rotic-spotting type of resistance to the mosaic virus. Tobacco PI’0dl1(ZIi0ll
From among the lumdreds of red clover plants test- (Confirmed ffvm Pflge 5) 91.
ed, several that developed necrotic spots were selected upon the development of mechanical methods of _ `
and increased as clones. Six of these clones were se- housing the tobacco. increased harvesting efficiency -7
lcctcd for further comparison. Clones KyC6 and K) C- would only magnify the housing problem which is a ·;
Tl originated as plants selected among survivors of critical problem from the standpoint of efficient utili-
some seedlings of Kenland red clover that had been zation of labor.
inoculated with a fungus that causes southern an- The functional requirements for housing stalk cut ,
thracnose. Clone KyC71-8 is from a plant selected from tobacco in conventional housing facilities were estab-
a group grown from seed produced on a plant of clone lished by a careful study of publications and observa— I
KyC7l growing outdoors, i.e. open pollinated. Clone tions of housing techniques employed by farmers.
KyC4(l is from a plant selected in 1953, growing with- These requirements were utilized in the development ` 
out symptoms in the midst of infected plants in a of the principal components of a machine for housing .
field of 3-year-old Kenland. Clones KyC4()-1 and KyC- stalk-cut tobacco. A prototype was constructed and its ;»
40-2 are from plants from seed produced on a plant operation was observed. A full-scale machine was con- _
of Ky(Z4(l growing outdoors in a cage with several structed and its operation was observetl. A full-scale tl
other 1iccrotic-spotting clones. machine will have to be constructed and tested V
These clones were selected because of their necrotic thoroughly before recommendations can be made on
spotting reaction and also because of their freedom the general use of the housing machine. —
 
6 Krzxrucxr FARM AND Home Scn;Nca—SUstsmn 1959
  }