CORRELATED INHERITANCE OF BOTANICAL CHARAC¬ 
TERS IN BARLEY, AND MANNER OF REACTION TO 
HELMINTHOSPORIUM SATIVUM 1 
By Fred Griffee, 2 Assistant Plant Breeder , Department of Agriculture , University 
of Minnesota 
INTRODUCTION 
The identification of linkage groups 
and their relation to chromosome 
numbers is a subject of general genetic 
interest. In only one organism, Dro¬ 
sophila, have all of the linkage groups 
been thoroughly worked out. Studies 
are being made of other organisms, 
however, with the idea of identifying 
the chromosomes by the behavior of 
the factors which they carry. Much 
has been learned of the factor relations 
in maize, largely from the efforts of 
Emerson and his coworkers. It is 
obviously a more difficult task to 
establish 10 linkage groups, which is 
the number of chromosome pairs in 
corn, than it is to establish 4 such 
groups, as in Drosophila. For linkage 
studies, an organism with a small 
number of chromosomes is desirable 
and from this standpoint, perhaps, 
barley offers as favorable material as 
can be found among the crop plants. 
Furthermore, barley has a number of 
easily distinguishable characters. 
Through the introduction of new 
plant varieties from foreign countries 
and as a result of extensive hybridi¬ 
zation studies, new characters are 
frequently being made available, and 
some of these have considerable eco¬ 
nomic importance. A 6-rowed variety 
of barley with smooth awns and resist¬ 
ance to Helminthosporium sativum has 
been developed and promises to take 
the place of the best 6-rowed varieties 
now generally grown in Minnesota. 
No such 2-rowed variety is known, 
however. Since there is a demand for 
2-rowed barleys in certain sections of 
Minnesota, the production of a 2- 
rowed variety with smooth awns and 
other desirable characters is of some 
economic importance. 
REVIEW OF LITERATURE 
A somewhat comprehensive review 
of literature on barley inheritance 
was made by Hayes and Garber (8 ). 3 
The literature review in the present 
paper indicates the important work 
on barley inheritance in its various 
phases, but the discussion of that 
work has been somewhat limited on 
account of lack of space. 
CYTOLOGICAL STUDIES 
The chromosome number for barley 
was reported first by Nakao (13) and 
later by Ubisch (23, v. 25 ). Nakao used 
a variety of Hordeum distichon and 
found the somatic number of chromo¬ 
somes to be 14. The same number of 
chromosomes was found by Ubisch in 
varieties of H. distichon and H. vulgare . 
INHERITANCE OF DIFFERENTIAL 
CHARACTERS 
Fertility of the lateral florets .—The 
results obtained from crosses of 2-rowed 
with 6-rowed varieties vary. Hayes 
and Garber (8) state that “the most 
frequent result is an intermediate con¬ 
dition in Fi in which the lateral florets 
are awned, but produce little or no 
fruitfulness. In F 2 a 1:2:1 ratio of 
6-rowed, intermediate, and 2-rowed 
forms is obtained. Six-rowed and 
2-rowed forms breed true to these 
respective characters in later genera¬ 
tions. Results of this nature can 
easily be explained on a single main 
factor difference.” 
Some crosses of 6-rowed with 2- 
rowed forms yield different results 
from the above, however, as was 
shown by Harlan and Hayes (6). 
The 6-rowed parent carried two fac¬ 
tors for fertility of the laterals, one 
for 6-rowed and another for interme¬ 
dium which is hypostatic to the 6- 
rowed factor. There were indications 
that sometimes modifying factors were 
present which affected the degree of 
fruitfulness in the laterals of the inter¬ 
medium form. Results of some crosses 
1 Received for publication July 3,1924; issued July, 1925. A paper submitted to the faculty of the Univer¬ 
sity of Minnesota in partial fulfillment of the requirements for the degree of doctor of philosophy. 
Published with the approval of the Experiment Station Director as Paper No. 479 of the Journal Series. 
2 The writer wishes to express his appreciation for the helpful suggestions of Drs. H. K. Hayes, E. C. 
Stakman, and C. O. Rosendahl. Thanks are also due J. J. Christensen for cultures of Helminthosporium, 
and to E. B. Lambert for assistance in taking some of the data. 
3 Reference is made by number (italic) to “Literature cited,” p.933. 
Journal of Agricultural Research 
Washington, D. C. 
( 915 ) 
Vol. XXX, No. 10 
May 15, 1925 
Key No. Minn. 55 
