42 
AGRICULTURE: L. R. JONES 
DISEASE RESISTANCE IN CABBAGE 
By L. R. Jones 
College of Agriculture, University of Wisconsin 
Communicated by R. A. Harper, December 31, 1917 
The cabbage, while ordinarily one of the most vigorous of cultivated plants, 
is highly susceptible to certain parasitic diseases. The most destructive of 
these, known as 'yellows,' is due to a soil inhabiting fungus (Fusarium con- 
glutinans) which invades the root system. Once introduced this parasite 
may persist indefinitely in the soil rendering it ' cabbage sick' so that this crop 
can no longer be grown upon it. One who knows the nature of this parasite 
and its manner of host invasion would have little hope of its practical con- 
trol through any of the usual methods of spraying or seed or soil treatment. 
Extensive experimental trials have justified this conclusion. 1 On the other 
hand, when we were called upon in 1910 to investigate this disease and its 
control in Wisconsin, it was these very factors which encouraged the hope 
that it might be possible to secure disease resistant varieties or strains. The 
principle involved in such an undertaking is, of course, that of ' the survival 
of the fittest.' The things essential to any satisfactory progress are that 
there be among the host plants well marked variations in individual suscepti- 
bility or ' resistance' to the parasitic attacks and that this character, whatever 
its cause, be fixed and transmissible from generation to generation. Another 
very important matter, from the practical standpoint, is that such resistant 
characters be combined with those which give the plants economic value. 
Examination of the worst diseased fields led to the discovery of certain indi- 
vidual plants which developed apparently normally although all neighboring 
plants were dying or dead from the effects of the parasite. Moreover, among 
these survivors were to be found representatives of the best commercial 
types. The first and last conditions were therefore met. Would these 
characters persist in seed obtained from such plants? 
Somewhat over 50 such resistant individuals were selected in the autumn of . 
1910, seed was grown from them in 1911, and in 1912 this seed planted, each 
' head strain' separately, on the ' sickest' available soil. Omitting all details the 
general results may be summarized by the statement that in every case the 
selected head strains transmitted in considerable degree their resistant qualities, 
and certain of them did so in high degree. Thus of the control (non-selected) 
varieties the majority were killed by the parasite and most of the balance 
were so diseased that they failed to form heads, whereas the poorest of the 
selected head strains proved decidedly superior to the best of these controls, 
and of the best selected head strain 98% of the plants lived through the 
season and 93% of them formed heads. The figures which may best be 
cited are, however, those comparing the head strain which in the behavior 
