UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT BULLETIN No. 1164 
Washington, D. C. 
August 10, 1923 
SEGREGATION AND CORRELATION OF CHARACTERS IN AN UPLAND- 
EGYPTIAN COTTON HYBRID. 
By Thomas H. Kearney, Physiologist in Charge, Office of Alkali and Drought 
Resistant Plant Investigations, Bureau of Plant Industry. 
CONTENTS. 
Page. 
1 
3 
Evidence from F 3 of segregation in the 
Holdon-Pima hybrid in characters not giv- 
ing definite Mendelian ratios in F« 
Extraparental characters in F2 of the Hol- 
don-Pima hybrid 
Sterility in F2 and F3 of the Holdon-Pima 
hybrid 
Correlation of characters in F2 of the Holdon- 
Pima hybrid 
Practical significance of the results 
Summary 
Literature cited 
Page. 
Introduction 
Ancestry of the hybrid 
Characters distinguishing the Holdon and 
Pima varieties 4 
Characters of the first-generation hybrid 6 
Definition of the characters measured or 
graded 7 
Statistical constants of the parental and of 
the Fi and F 2 hybrid populations 11 
Frequency distributions of the second genera- 
tion of the hybrid 15 
Mendelian segregation in the Holdon-Pima 
hybrid 21 
Data of the Holdon-Pima hybrid compared 
with evidence from other sources of Mende- 
lian segregation in cotton hybrids 27 
INTRODUCTION. 
The inheritance of characters in hybrids between different varieties 
of the Egyptian type of cotton was discussed in an earlier paper (28) 1 . 
The parent varieties, Pima and Gila, differed significantly in respect 
to 24 size and shape characters. The hybrid modes and means for 
most of these characters were approximately intermediate in F, and 
F 2 and no extraparental characters appeared in F 2 . The inheritance 
was of the " blend" type, the frequency distributions of F 2 having 
been unimodal. The second generation was more variable than the 
first in some but not all of the characters, but the differences in va- 
riability between the two generations were relatively slight. These 
facts indicate, according to the current interpretation, that the char- 
acters in question involve several factors. Comparison of the coef- 
ficients of correlation of 40 character pairs in the first and second gen- 
erations of the hybrid gave no evidence of the existence of genetic 
correlation or coherence (8). 
Subsequent study of the data indicated that, although the distri- 
butions were unimodal, segregation had in fact occurred in the second 
The serial numbers {italic) in parentheses refer to "Literature cited.'' at the end of this bulletin. 
42433—23 1 
