SEGREGATION OF SUSCEPTIBILITY TO PARASITISM IN 
MAIZE 
Donald F. Jones 
Various degrees of immunity, shown by cultivated plants to the 
attacks of parasitic organisms, have been recorded. Resistance of 
cotton, cowpeas, and melons to fungus injury has been reported by 
Orton (i, 2, 3), of potatoes by Stuart (4), and of flax by Bolley (5). 
Webber and Orton (6) have shown that the same variety of cowpeas 
which is resistant to wilt is also markedly resistant to the root knot 
nematode. Gernert (7) also states that teosinte and first generation 
teosinte-maize hybrids are not subject to injury by aphids which 
attack maize. 
The inbred strains of maize carried on at the Connecticut Experi- 
ment Station, reported by East and Hayes (8), which have been con- 
tinuously selfed to the present time, show striking differences in the 
number of plants affected by the smut fungus (Ustilago zeae (Beck.) 
Ung.) and an unidentified leaf blight organism. In 1915 a few inbred 
strains of flint maize were badly injured by this leaf blight organism. 
Again in 191 6 the same strains were affected in the same way, every 
plant being badly injured, while other selfed strains derived from dif- 
ferent varieties and grown in adjoining rows were almost entirely 
unaffected. First generation hybrids of these susceptible strains with 
resistant types were grown in the same field and were only slightly 
damaged. 
In 19 1 7 no injurious effects of this nature could be seen on any 
plants. Several different strains, however, were badly attacked by 
smut. In table i are given the number of plants grown and the 
number of plants affected of sixteen different selfed strains of maize, 
inbred from nine to eleven generations. The relation of these to each 
other is shown by the pedigree numbers. Twelve of these were derived 
from one original variety. Of these, three strains were started from 
single plants in the first generation of inbreeding and numbered 1-6, 
1-7, and 1-9. In the third generation from 1-7 two lines were started, 
1-7-1-1 and 1-7-1-2, and continued. After the, seventh generation 
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