A Database for Triticeae and Avena
II.31. Allelism testing of seven chlorina mutants in Trebi barley.
Michael McMullen. Department of Agronomy, Colorado State University,
Fort Collins, Colorado 80521, U.S.A.
The spontaneous chlorina mutants of Trebi barley collected by D.W. Robertson
at Colorado State University were tested for allelism among themselves
and with the collection of designated chlorina mutant stocks: f,
f3, f4, f5, f6, f7,
f8, f9. The Trebi mutants, normal green plants, and designated
chlorina stocks were crossed reciprocally in a sufficient number of combinations
to determine the allelic relationship of the chlorina genes and the type
of inheritance of the chlorina character.
The F1 phenotypes of crosses using Colsess V (fcfc)
as the female parent and the Trebi mutants as the male parent are presented
in Table 1. Using Trebi VI, Trebi X, Trebi XII and Trebi XIII as the male
parent resulted in all green F1 progeny, indicating these mutants are not
allelic to fc. The F1 progeny resulting from crosses
using Trebi V, Trebi IX and Trebi XI as the male parent were all chlorina,
indicating that these mutants are allelic to fc.
Table 1. F1 phenotypes of Colsess V (fcfc)
x Trebi mutants.
The F1 phenotype of crosses among the Trebi mutants and normal green
plants is presented in Table 2. The crosses among Trebi V, Trebi IX and
Trebi XI resulted in all chlorina F1 progeny. This verifies allelism of
these mutants which were previously shown to be allelic to fc.
Table 2. F1 phenotype of diallelic crosses among
Trebi chlorina mutants. Number is number of F1 plants observed.
All of the F1 progeny resulting from crosses using Trebi VI, Trebi X,
Trebi XII and Trebi XIII as the female parent were chlorina, while the
F1 plants resulting from crosses using these mutants as the male parent
were green, except in cases involving one of these mutants as the female
parent. The reciprocal difference in those crosses is attributed to maternal
inheritance of the chlorina character.
The mutants suspected of being maternally inherited, Trebi VI, Trebi
X, Trebi XII and Trebi XIII were crossed reciprocally with normal green
plants. All crosses using these mutants as the female parent and normal
green as the male parent produced chlorina Fl progeny. The reciprocal crosses
using normal green female parents produced only normal green progeny, verifying
the maternal inheritance of these Trebi chlorina mutants.
Three other maternal chlorina stocks have been observed, Coast V (Robertson,
1937), Trebi VIII and Trebi 67-8043A (Tsuchiya and Robertson, 1971).
The F2 generation from crosses involving the maternally inherited Trebi
chlorina mutants was grown to verify the maternal inheritance. The F2 of
crosses using normal green as the female parent and maternally inherited
chlorinas as the male were all normal green, exhibiting no segregation
for the chlorina character and indicating no genetic control of the chlorina
character. The F2 of crosses using the maternally inherited chlorinas as
the female parent and normal green males were all chlorina.
Crosses using a maternal chlorina as the female and a nuclear chlorina
as the male parent were all at least as light in color as the female chlorina
parent. Plants ranging in color from albino to slightly lighter than chlorina
were also observed in the F2 populations. These plants were attributed
to the segregation of homozygous recessive nuclear chlorina genes interacting
with the maternally inherited chlorina factor.
A particular segregating nuclear gene interacting with the various types
of chlorina cytoplasm was expressed differently in the different maternally
inherited chlorina cytoplasm types of Trebi VI, Trebi X, Trebi XII and
Trebi XIII. Using this criterion, it was concluded that the four maternally
inherited Trebi chlorina mutants are distinct from each other, conditioned
by four separate maternal systems.
Since four types of maternal chlorina inheritance were found and 3 others
have previously been observed, it seems likely that cytoplasmic inheritance
may play an important role in the inheritance of chloroplast characters.
Polymorphism may exist in chloroplasts, or at least in cytoplasmic factors
controlling their development. Many, more subtle characteristics than color
phenotype are probably inherited other than through nuclear genes. This
being the case, the choice of a female parent to be used by breeders would
be a fundamental concern.
Robertson, D. W. 1937. Maternal inheritance in barley, Genetics 22:104-113.
Tsuchiya, T. and D.W. Robertson. 1971. Two more cases of maternal inheritance
of chlorina mutation in barley. Barley Genetics Newsletter 1:65.
BGN 2 toc
BGN Main Index