cLfn ROOT or imc ikers 



119 



l>y Hiilsti-d ('J»!>). R.-ivn (,'11). Cunningliam {'it), 

 Anony.. (Nova Si-otia. :>3). I-indfors ('at, '25), 

 ■r.iiiunt ('•-'■). '30. '.•tn.Ciil.ks ("31). rindlay ('31). 

 Mad. rod ('31). Ihiidru'k ('32). Ik'.iuiiKiiit and 

 .•^taiiiland ('33. '31-). Walker and I.arsiii ('31.). 

 WalkiT (^'3(>).()lsson ^'3!>. 'K)). Hriv.liniv ('3<t) and 

 Pryor ("10). Early \\'ihte Milan and Early 

 Snowball showi-d only 1.1 per cvnt to O.G per cent 

 susoi'ptibility, accordiiifi to t'unniniiliani. 



Swedes in general .-ire reported to l)e more resi.st- 

 ant tlian turnijis. but tliey likewi.se exliiliit a wide 

 ran<;e of .susceptibility and resistance, 'llie following 

 v;irieties: 



Balmoral Ostergiita 



IJ.ingholm Otofte 



Bangliolm Hcrning Sweet German 



Bangliolin .Studsgaard .Sweet Russian 

 Danish N'arieties !■ and White Necklace 



'2ii White Russi.m 



Green Top Swedish White Swede 



Ma j rova \\'ilheuisburger 



May 



have been reported by Ravn ('H). Cunningham 

 ('1 t). .\nony., (Nova Scotia, '23), Lint'ors ('21., '25), 

 Whitehead ('22, '25). Hockey (•26).Gussow ('26), 

 Tenncnt ('25. '30. '3I-), Davis, Griffith, and Evans 

 ('28). Osterwaldcr ('29). Gibbs ('31), Findlay 

 ('31). MacLeod ('31). Beaumont and Staniland 

 ('33. '31). Walker and I.arscn ('31-). Olsson ('89. 

 '40). Bennett ('39). and Pope ('39) to be relatively 

 resistant. Ravn ('11). I.indfors, Ciiissow, and Pope, 

 however, found that the so-called resistant Bang- 

 iioLM PfRPLE Top. Studsraard Bangholm, Wil- 

 HELMsniRGER. and Yellow Tankard varieties may 

 be 100 ))er cent infected and completely destroyed. 

 Cabbages, likewise, show a wide range of suscepti- 

 bility to club root, and none of the commercial varie- 

 ties are highly or eomiiletely resistant, according to 

 Cunningham, I.indfors, \\'alker and I.arsen. .lania- 

 lainen, and others. 



.\11 Seasons Dark Red Erfurt 



.\mager Hvidkaal 



.\meriean Savov Mammoth Red Rock 



Blomkaal Perfection Savoy 



Braunsweig Gribkova Rodkaal 



Braunsweig Hos Hos \'olga 



Brunswick White Russian 



Copenhagen 



have been reported by Ravn ('08), Cunningham 



('12. 'U). Naumov ('25, '28), Rochlin ('33). and 



Fedorintschik ('35) to be particularly susceptible. 



-Ml of these varieties may show 98 per cent to 100 



])er cent clubbing in badly infested soil. On the other 



hand. 



Blue Large Late Flat Dutch 



Bodenkohlrabi Late Moscow 



Bronka Red 



Griinkaal .Short Stiinmed Amager 



Henderson's Early Sum- Slovianka 



mer .Stone Maxon 



Hollander Valvatievka 



are said to be less susceptible (C'unuinghani, ' 1 !■ ; 

 Hdstermann. '22; IL-irter and .Jones, '2t; Oster- 

 waldcr. '29; Tedin. '3:i ; Motte. '33; Fedorintschik, 

 '3(1 ; 15re/,hnev '39). 



U.idishes are also very susceptible to club root, 

 and it is doul)tful whether any eomi)letely immune 

 eonunereial varieties exist. Halsted ('99) reported 



tJIANT StI'TTCiART, LoN(i BlaI'K Sl'ANISII, NeW- 



coMu White, and Yellow Summer Ti'rnip to be 

 wholly free from clubbing. Cunningham found that 

 susceptibility varied from 92.2 per cent in Long 

 Scarlet Radish to 5.6 jier cent in Giant Stutt- 

 gart. In addition to the latter variety. Early Scar- 

 let Turnip, Delikatess, DHKiKNiiHrNNEN, Im- 

 mune, Long Black Paris A\'inter, Ruuin. and 

 Sa.xa have been reported by Cuiuiingham (ll), 

 Gleisberg ('23) and .Jamalainen ('36) to be fairly 

 resistant. 



Other commercial cultivated crucifers have not 

 been so extensively studied for varietal resistance as 

 those noted above. Cunningham and .Jamalainen 

 found all varieties of kohlrabi to be very susceptible, 

 but Schatt'nit reported that the varieties which he 

 studied were relatively immune. Honig ('32) tested 

 five varieties of kohlrabi and found the following 

 incidence of infection: (jelbe Schmalz 7.3 per cent, 

 AVeisse Schmalz 27.7 per cent, Weisse Wester 

 per cent, Gelbe Wester 32.6 per cent. Apfel gelb 

 6.2 per cent. Among Brussel sjjrouts. Hercules is 

 fairly resistant (.Jamalainen, '36). All varieties of 

 cauliflower are equally susceptible, according to 

 Cunningham, Lindfors, and Jamalainen. Marrow 

 Stem and Dreinenbrunnen Curley Kale are said 

 to be highly resistant by Osterwalder, and Beaumont 

 and .Stanland, while April Queen and Victory 

 broccoli were found to be resistant by Bailie and 

 Muskett. Rape shows almost 50 per cent susce]5tibil- 

 ity. according to Cunningham, but (ileisberg re- 

 ported it to be immune to club root. Ssacharotf and 

 Rochlin also reported B. Napiis var. S. esculenta to 

 be immune. One variety of B. Rapa sliowed 100 per 

 cent susceptibility, while another exhibited only 

 10.9 iJcr cent clubbing, according to Cunningham. 

 Gleisberg. however. re])orted B. rapa to be unsus- 

 cejitible. Mustard is rejjorted to be highly susce])tible 

 by Hcistermann. while Cunningham. Naumov. Motte 

 and Rochlin found black mustard to be highly resist- 

 ant or completely immune. Chinese cabbage sliows 

 100 per cent suscejitibility. according to Naumov and 

 Katterfeld. 



Nature of Siisceptihility and Resistance. — The 

 differences in degree of infection exhibited by the 

 wild .ind cidtivated crucifer varieties listed above 

 were believed by some w-orkcrs to be l)artly due to 

 the ))rescnce of more or less virulent biological 

 strains of P. Brasxicae which are sjjceitic for certain 

 hosts. Considerable doubt has been ex))ressed about 

 the presence of such strains and it is rather generally 

 believed that relative susceptibility and resistance 

 are largely inherent host characters. The nature of 

 resistance is not yet well understood, but .Ssacharoff 

 believed it to be due to substances in the cell sap. 



