Tải bản đầy đủ - 0trang
IX. Allelic Series at the Maturity Gene Loci
Frequency Distribution of Flowering of Parental and FZPopulations of Combine Hegari X 1 W a y Milo and
Combine Hegari X Hegari Grown at Plainview, Texas, in 1965
CH X H
C H X lOOM
J. R. QUINBY
The dominant at locus 1 in Combine Hegari ( M a , M a , ma3M a , )
probably came from Hegari, and the dominant at locus 2 must have
come from Hegari. Dominant M a , in Combine Hegari must have come
from Milo, Hegari is M a , M a , M a , m a , and 100-day Milo is M a , Ma,M a , Ma,. The latest genotype. in each F, population is homozygous
dominant at all 4 loci, In the latest plants of the F, of CH x lWM, at
least one dominant at each locus would have come from Milo. In the
F, of CH x H, all dominants at loci 1, 2, and 3 came from Hegari and
only dominant M a , came from Milo. The latest plants in the F2 of
CH x lOOM flowered in 90 to 92 days, The latest plants in the F, of
CH X H flowered in 84 to 86 days, a difference of 6 days. These data
indicate that dominants at loci 1, 2, and 3 from Milo interact to cause
more lateness than dominants at loci 1,2, and 3 from Hegari.
Texas Milo originated from one Periconia root-rot resistant plant
that was selected along with more than 1,oO others from a diseased
field in Runnels County, Texas (Quinby and Karper, 1949). All the
selections were grown at Chillicothe, Texas, and, although all the
progenies looked like Dwarf Yellow Milo, small differences in maturity
existed among them. Finney Milo originated at the Garden City, Kansas,
Experiment Station as one of two Periconia root-rot resistant plants
found in a diseased plot (Wagner, 1936). Both Finney and Texas Milo
are of the genotype M a , maz ma, Ma,, but Finney Milo heads about 2
days later than Texas Milo. The difference in maturity between the two
varieties is thought to be due to an allelic difference at one locus, probably locus 1. Similar small differences in maturity exist among strains
of Blackhull Kafir that were found growing on farms in Texas, Oklahoma,
and Kansas in the 1920’s and are still preserved in sorghum nurseries.
These small differences in maturity are thought to be allelic and not to
be due to modifiers.
Allelic designations were not assigned to the genes in Table XIV
but will be in the discussions that follow.
The recessive maturity alleles at the first locus in grain varieties of
American origin came from Early White Milo, Blackhull Kafir, Red
Kafir, Pink Kafir, or Feterita. The Red and Pink Kafirs and several sorgos
from South Africa, the Feteritas and Durras from the Sudan, the Durras
from the Middle East, and the Kaoliangs of Manchuria were all recessive
at the first locus when they arrived in the United States. The recessives
at the first locus in the Sooner Milos and in Blackhull Kafir probably
occurred as mutations in the United States.
The following are the designations of the known alleles at locus 1:
MATURITY GENES OF SORGHUM
MalM-from Milo and in Fargo
MalH-from Hegari and in Early Hegari
malF-from Bonita and Combine Bonita that come originally from
either Feterita or Blackhull Kafir
malB1-from Texas Blackhull Kafir
malc-from Combine Kafir-60 but of unknown origin
malB2-from Redlan but originally from Blackhull Kafir C171
malP1-from Pink Kafir CI432, arid in Kalo and Early Kalo
malK-from Red Kafir PI19492
malp2-from Pink Kafir PI19742
malE-from Combine 7078 and probably in TX414 but of unknown
malB3-from Caprock but originally from Dawn Kafir
malD-from Durra PI54484
The allelic series at the first locus must be much longer than shown
because the recessives in the Kaoliangs of Manchuria, the numerous Feteritas and Durras of the Nile Valley, and the many sorgos from South
Africa must all be different. Likewise, the dominants at locus 1 in
many tropical varieties must be unlike the dominant Mu;s from Milo
C. ALLELESAT THE SECONDMATURITY
Of all the varieties identified for maturity, only SMW, SM80, 60M,
8OM, Kalo, and Fargo are recessive at the second locus and the recessive is the same in each of them, For this reason the only known recessive allele at the second locus is the one in the Milos. The dominant
alleles at locus 2 are more numerous and those that are known are listed
Bonita but originally from Feterita or Blackhull Kafir
Texas Blackhull Kafir
Redlan but originally from Blackhull Kafir C171
Red Kafir PI19492
Pink Kafir PI19742
Pink Kafir (21432 and probably in Early Kalo
Caprock but originally from Dawn Kafir
Milo and in Fargo and Kalo
J. R. QUINBY
When Periconia root-rot resistant strains of Milo were being picked
up on farms in the 193(Ys, plants of the following maturity genotypes
were found: Mal maz ma, Ma,, M a , ma2M a , Ma,, and mal M a , Ma, Ma,.
It is probable that the first two genotypes did not originate at the same
time and there are probably two recessive mutations preserved in Milo
at the second locus.
Many varieties from different areas of Africa and Asia are dominant
at locus 2 and it is likely that the many dominant Ma:s are not identical.
A mutation to early maturity at locus 3 in Milo occurred before
1905 because the genotype M a , maz ma, M a , was being grown in Texas
by that time. An allelic series at maturity locus 3 has been reported
previously (Quinby and Karper, 1961). Early Hegari is recessive at
locus 3, and because of its different origin, recessive ma3 from Early
Hegari should be unlike recessive ma, from Milo. Recessive ma3 in
Bonita probably came from Feterita. Because Milos have been one of
the parents of many crosses, the recessive ma, in many varieties of
American origin came from some Milo. The known alleles at locus 3
M ~ 3 ~ - f r o mHegari and-in Combine Bonita
M~3~l-frorn Texas Blackhull Kafir
Redlan but originally from Blackhull Kafir C171
Pink Kafir CI432 and in Kalo and Early Kalo
M ~ ~ ~ - f r o rRed
n Kafir PI19492
M ~ ~ ~ ~ - f rPink
o m Kafir PI19742
M ~ 3 ~ ~ - - f r oCaprock
but originally from Dawn Kafir
M ~ 3 ~ C f r osome
m Blackhull Kafir and in Fargo
rn~3~-from Ryer Milo
rn~3~-from Durra PI54484
rn~3~-frorn Combine 7078
Many tropical and many temperate zone varieties that have been
introduced into the United States are dominant at locus 3; the dominants
are not identical so the allelic series at locus 3 must be long.
MATUFUTY GENES OF SORGHUM
Recessive mu4 was found in Hegari and occurs in Early Hegari also
but has not been found elsewhere. Dominant Ma, occurs in the Milos
and in many other varieties and so the allelic series at locus 4 must be
long. The known alleles at locus 4 are the following:
M ~ ~ ~ - f r oMilo
m and inrCombine Hegari
M ~ ~ ~ - f r oBonita
but originally from Feterita or Blackhull Kafir
M ~ ~ ~ - f r o Combine
Texas Blackhull Kafir
M ~ ~ ~ ~ - f rRedlan
o m but originally from Milo or Blackhull Kafir C171
Ma4P1-from Pink Kafir (21432
Ma4K-from Red Kafir PI19492
Ma4p2-from Pink Kafir PI19742
M ~ ~ ~ - f r oCombine
M~$~-from Caprock but from either Milo or Dawn Kafir
M ~ ~ ~ - f r oDurra
ma4H-from Hegari and in Early Hegari
F. ALLELESAND RESPONSE
SM100, Combine Bonita, Texas Blackhull Kafir, Redlan, Early Kalo,
Caprock, and Pink Kafir CI432, all have the same genotype for maturity
as far as dominants and recessives at the four maturity gene Ioci are
concerned. Yet they vary in days to flower from 56 to 70 days. Likewise,
SM90, Bonita, Combine Kafir-60, PI54484, Combine 7078, and TX414 are
genetically identical as far as dominants and recessives at the four gene
loci are concerned. Nevertheless, they vary in time of flowering by as
much as 6 days.
Within the first group that has the genotype ma, Mu, M a , Ma4,
SM100, Combine Bonita, and Early Kalo are quite sensitive to photoperiod. Texas Blackhull Kafir and Redlan are relatively insensitive to
photoperiod and the response of Caprock and Pink Kafir CI432 is unknown. Within the second group that has the genotype mal Ma, ma, Ma4,
SM90 and Bonita are sensitive to photoperiod. Combine Kafir-60 and
Combine 7078 are less sensitive, and Combine Kafir-60 is later in flowering in Jamaica in the winter than varieties that are much later in flowering in Texas in the summer.
The inferance here is that the differences that exist in time of flowering among varieties within a genotype are allelic and that different
alleles differ in response to temperature, some alleles being more temper-
J. R. QUINBY
ature sensitive than others. If this is true, it is logical to assume that the
four maturity gene loci control response to photoperiod and that alleles
that differ in temperature response influence the response to photoperiod
differently. How photoperiod and temperature interact to control time
of floral initiation is still not known, but it seems obvious that both
photoperiod and temperature operate through the same gene loci.
As shown in Table XIV, interaction of dominants and recessives
at four gene loci result in times of flowering that spread from 44 to 90
days. Because only four gene loci have been found and because multiple
allelic series must exist at each locus, it seems unnecessary to assume
the existence of numerous gene loci to account for the continuous variation seen in time of flowering in the sorghum species.
Winter and spring growth habits in cultivated barley, Hordeum
sativum Jess., have been attributed to 3 gene loci by Takahashi and
co-workers in work that has been reviewed by Takahashi (1955).
Variation in time of flowering among the varieties with spring growth
habit or differences in low temperature requirement for removal of the
winter nature were attributed to different multiple alleles of the spring
Barley is a long-day species whereas sorghum is a short-day species.
Nevertheless, the genetics of maturity in the two species is similar, and
it is likely that maturity in all plant species is controlled by a few gene
loci and allelic series at those loci.
of Time of Floral Initiation on Plant Size
Under 10-hour photoperiods in the field at Chillicothe, 2-dwarf
genotypes of the Sooner 90, 60-day, 80-day, and 90-day Milos initiated
heads at the same time and flowered simultaneously. In this short-day
environment, the several genotypes were obviously similar in size and
were quite small. Under 14-hour photoperiods, the four genotypes were
quite dissimilar in size, the earliest in maturity being the smallest and
the latest, the largest. Part of the data obtained from a planting at
Chillicothe, Texas, in 1944 is shown in Table XVI. The data show that
dominance in the 90-day genotype Ma, Ma, ma3M a , as contrasted to
recessiveness at the first locus in the SM90 genotype, ma1 Ma, ma3Ma,,
increased duration to flowering by 53 days, leaf number by 92 percent,
height by 77 percent, and more than doubled total dry weight of plant.
When growing conditions are favorable, there is correlation of early
maturity with low yield and late maturity with high yield. The positive
regression of grain yield on maturity in sorghum hybrids has been discussed by Dalton (1967). In most tests under favorable conditions, each
increase of one day in duration to flowering increases grain yield by
MATURITY GENES OF SORGHUM
Influence of Dominance or Recessiveness a t Locus 1 on Plant Growth in Milo
Grown under Normal Photoperiods a t Chillicothe, Texas, from a Planting Made
on June 20, 1944a
Number of days to anthesis
Number of leaves
Height of plant, cm.
Length of leaf, cm.
Weight of heads, g.
Weight of plant, g.
Data from Quinby and Karper (1945).
about 100 to 200 pounds of grain per acre. Because of this regression,
days to flower must be considered in evaluating hybrids using the results
of yield trials.
Maturity Gene Loci and Heterosis
No critical data exist in sorghum to show that hybrids grow faster
than varieties, but it has been shown that hybrids grow to be more than
50% larger than parent varieties in a few days less time (Quinby, 1963).
For this reason, it is reasonable to assume that rate of cell division must
be greater in hybrids.
Greater tillering is a manifestation of heterosis in sorghum (Quinby,
1963), and heterozygosity at one maturity locus has been reported to
cause greater tillering and greater head yield (Quinby and Karper,
1946). Some of the data are presented again in Table XVII. In 1942,
plants in a row segregating only for maturity were harvested and grown
the next year to identify the homozygous and heterozygous plants. The
Effect of Heterozygosity a t Locus 1 on Time of Flowering, Amount of Tillering, and
Weight of Heads of Homozygous and Heterozygous Milo Plants a t
Chillicothe, Texas, in 1942c
Data from Quinby and Karper (1946).