June 23, 1923 
Inheritance of Resistance to Puccinia graminis 
991 
Table VI .—The reaction of the parent varieties and families of MindumXPentad 0 
biologic Form XXXIV. 
Parent vai ieties 
or Fs families. 
Mindum 
Do. 
Do.. 
Total 
Pentad. 
Do. 
Do. 
Total. 
Do. 
Do. 
Do. 
Do. 
Total. 
Class of infection. 
Heterozygous. . . 
Near-susceptible. 
Susceptible. 
Resistant.. 
Near-resistant. . 
Heterozygous.. 
Resistant. 
Near-resistant... 
Heterozygous. . . 
Near-susceptible. 
Susceptible. 
Distribucion of F3 plants according to the type of 
infection shown. 
37 
3 
40 
38 
12 
38 
II5 
18 
135 
53 
29 
48 
88 130 
X 
131 
24 
9 
164 
95 
53 
400 
8 
17 556 
x+ 
2 
7 
39 
144 
4 
I 
149 
8 
232 
47 
39 
326 
14 
31 
273 
48 318 
139 
90 
109 
338 
Total 
pots of 
parent 
vari¬ 
eties 
or F3 
fami¬ 
lies. 
2 
4 
27 
33 
26 
5 
2 
33 
14 
6 
68 
II 
II 
no 
Infection appeared on 357 of the inoculated Pentad plants. Of these 
9 reacted with x + type infections and i gave a 4 type. The other 347 
Pentad plants gave a range of infection types from o to 3. Only 5 plants 
showed type 3 infections, therefore this type would appear not to belong 
to the range for the resistant parent. However, the type 3 infection is 
much more like the x— type than like the x + . In fact, experiments 
indicate that a variety of which the seedling plants give type 3 infection 
in the greenhouse is resistant in the field, whereas varieties showing x + in 
the greenhouse probably are not resistant in the field. Consequently, 
the 3 type infection may well be included in the range of the Pentad 
parent. Classification of Pentad pots gave 26 resistant, 5 near-resistant 
and 2 heterozygous (PI. 3). 
A comparison of the results obtained for Pentad in the study with the 
Kubanka No. 8 X Pentad cross with those obtained here reveals con¬ 
siderable differences in the number of plants showing the various types of 
infection. The two series of inoculations were made at different periods, 
and consequently the conditions -were not comparable. This strik¬ 
ingly brings out the fact that the value of the data taken on the hybrid 
material lays in the direct comparison made with the results from pots 
of parental plants grown under identical conditions. Reactions which, 
under one set of circumstances, would place an Fg family in the near- 
resistant class might, under other circumstances, cause it to be classed as 
heterozygous, depending on the parental reactions at each period. 
It was noticeable that both parent and hybrid plants showed an abund¬ 
ance of hypersensitiveness to Form XXXIV. This probably accounts in 
great measure for the appearance of such large numbers of x — and x + 
types of infection. Sharp hypersensitive areas occurred around a large pro¬ 
portion of the uredinia of types 3 and 4 infections. Usually type 4 shows 
