151

The proportion of the recombimt classes of kernels on the ear of the
6704B—4 entered in table 45,
parent plant/and on that of its Y Spm/y+ progeny/was much the same, and
?
this amounted to approximately 18 percent of the total number of kerrnels.
It will be recalled that the same relative stability of locatiun of Spm
was exhibited by the Spm in plants in culture 66294 that were Y Spm/y +
(table 5) and by the majority of their Y Spm/y + progeny (table 29).
However, in these plants, Spm occupied a position in chromosome 6 more
distantly removed from Y. The reaqngbinant classes amounted to approximatel
35 percent. This same stability of location was expressed by Spm when
it occuppied a position/gtti FET aEgS em Eo Sy , and this was shown in plant
“ty!

6895A-1 and its progeny (table 43). In contrast to sais sain the two
cases examined in detail where Spm was located in chromosome 9,; Spm
underwent many transpositions and many of these, in turn, occurred early
/

Mp be Cu,
in plant development. That the chromosome in which Spm resides (is not
Gs not,

vmottnat Cobre! gig) te pond bat eye -

in itself the tnportent factor controlling Spm behavior was shown by a

——— “A

 

m1

case in the a5 cultures in which it was carried in chromosome 9.

W6A 4
This case has=been examined more extensively than any other. this Spm,

eobah web, “dio

residing at a site close to Wx, remained quite stable in location, altheaeh
A

aitougs uruelts

Franspositions of it do’ occur, late in development of sporogenous or svore

ng eretin 4
cells. Since this case has contributed much to an an ee of
152

inactivation of Spm, discussion of it will be postponed until t.is subject
is considered. At this time, however, another case of insertion of Spm
in chromosome 9 will be considered as it serves as an excellent illustration

of the high proportion of transposed Spm,in the Spm carrying recombinant

QT UL he neererbuy Te caustic prod Deg
peau

class of kernels that may be present jon a test cross ear. oun Q

aay Spin tio Lpention C mak b671F2). Vente THEE pegend

In the case sam to be considered, thm Spm was located in the wx
carrying chromosome 9 of a Wx/wx Pant and at a position that was probably
very close to wx. It was present at this location mn one plant in the

tested Srpampuxefx progeny of plant 6629A-5 (table 5). In plant 6629A-5
two Spm elements were present one of which was located in its Y bearing
chromosome 6. Tests were conducted with progeny derived from kernels
on the ear of the main stalk of this plant and on that of its tiller.
These plants were grown in the summer of 1954 under culture numbers
6671 and 6672.
From the earpf *thg >mman stalk, the Spm constitution was determined in
| por
20 plants derived from colotless, sh, kernels, 14 from the Y class (culture
A
ae
6671F) and 8 from the y class (culture 6671G). From the tiller ear, 27
plants derived from colorless, sh, kernels were examined for Spm constituion
?
aye
14 from the Y class (culture 6672E) and 13 from the y class (culture 6672F).
Among the total of 28 plants derived from the * kernels on these two ears,

aay Ye’? DAs

no evidence of Spm was given by tre kernelg on the testcross ears produced
A
158

aud yaw of
by 13 of them. Among the 15 plants having Spm, one was present in murs
pak clemuld war praca
10 of them,amd more than one, in each of the other five Plants. Spm was

bENIE-1, ET SE

oss

linked with Y only in two of the:.e ten plants (table 46)e having one Spm.

COT Our PlowT b671F-% o672 E+,
and with wx in "tte otherg (table 47) Aud powuyy Weel, Ley WQ fourth Creat).
In 4 of the remaining 6 plants in which one Spm was present, linkage of

ask
it with either Pr or wx could not be determined as these plants were

A
pe/pr, Wx/Wx in constitution. The other two plants were heterozygous for
alleles of these two markers but no linkage of Spm with either of them

was expressed. Iwo Spm elements were present in each of 4 of the 5

plants with more than one Spm element in them. Linkage of one of the Spm

f on eter fad a Mint b)
jig eb boty ay 4]
elements with Y was expressed in one of these 4 plants. In the fifth
j A
adi Led Hunde oveS pan elem Uh,

plant, at least 3 and probably 4 Spm elements were present.

Of the 19 tested plants derived from the colorless, sho, y class of
kernels in cultures 6671 and 6672, the testcross ear produced by two of
them showed no evidence of the presence of Spm in any one kernel. The
testcross ear producdd by the remaining 17 plants showed that each
had Spm, one being present in 16 of these plants and two being present in
the remaining plant. Linkage of Spm with wx could have been detected
only in 6 of these plants. Linkage of it with Pr could have been detected

in 10 of them. However, no clear evidence of linkage of “pm with these

markers was expressed in any of of these plants, ur udu. Wu» cous Lutuse bie
daha
Lot

Loa On three of the thirty-three ears produced by the Spm carrying
plants in cultures 6671 and 6672 a large sector appeared in which all
kernels within it were pale colored. This indicated that in each of the

three plants on whose ears these sectors appeared a change had occurred to

or Hiv TET 4) fe ee 2

Spm early in development of the plant, Howevexn,-“progeny tests were
dowd {eon Loud 06 27R - 5 GT wes wich

conducted only with one of the plants in these two cultured, | that in

  

-

Ups Ww : ;
which Spm was elk alia wx beawinge chromosome 9, ; cent
recombinetitn—with iF (Plant 6671F-2, table 47). Six plants were grown

from the ¥ and Wx class of variegated kernels on the testcross ear of this
plant under culture number 6873A and six other plants were grown from
the y and Wx class of variegated kernels under culture number 6873B.
With respect to Spm and the alleles of Wx, all plants were derived from
the Spm carrying recombinant class of kernels on this eur. All 12
plants were variegated.

Kighteen test cross ears were obtained from 9 of the 12 plants
in culture 687}3xandxakixukxthemxwerexvariegximaxx One Spm was present
in all tested parts of 7 of these plants and in noré of them was it linked
with Wx (table 47). “n one plant, 2 Spm elements were present in the
two tested parts of this plant. Neither of them was linked with Wx

plant 6873A-—3
(table 47). In the remaining piant, at ieast 3 Spm elements were
155

present in each of the Fee tested parts of this plant (plant 6873B-1,
table 47). It may be mentioned also that in none of the four tested
plants that were Y/y in consitution was evidence given of linkage of
the Spm in them with Y.

Spm carrying
In the/p2zrent plant of those in culture 6873, Spm was closely

lif

eit, F Cofyy y Vlety |

linked with wx (Plant 6671F-2, table 47). Of the 169 variegated kernels”
on its testcross ear, only 29 were in the Wx class. As the described

tests conducted with plants derived from 9 of these 29 kernels indicate,
(VAals wy wld) heer Munn bo Ap prlarce
xm none of these 9 kernels amese as the conse.uence of crossing over

Rote aad Ty aha

between: : Spm, aad WX. Transposition of Spm was responsible for their

appearance in this recombinant class of kernels. It is suspected,

aetach on typ Wee

therefore, that Spm in the parent plant, 6671F-2, was located very close }

tpl ome ©

to wx and that the majority, if not all, of the recombinant classes, SEOré

&
as the conse juence of premeiotic trans posi tiong of Spm.

YF We “nterslle2

Before tests of the Spm constitution in the progeny of plant 6629B-5%

"pug

(table 30) are considered, those conducted with the second generation yy
presented Ube, hol Seuterdiog Pode, aillus Lat
progeny of plant 6629A-~2 will be CORBEESESE. This second generatdbion

progeny was derived from thosf plants in the immediate progeny of plant

-2oe a vont
“Vibe -
156

6629A~2 in which a transposed Spm was present. They represented the

few cases in which a transposed Spm ele.ient was found to preepresent in

. \ wa eguatk alias

the progeny of plant 6629A-2., This plant was Y Spm/y+ as were most of
wy - ul

its * bearing progeny that carried Spm. However, the single Spm in
A

plants 6665G-12 and 6665G-21 was not linked with Y (table 24). % Plant

Y

Weegee TON Wier
6665E-10 (table 26) hed 2 Spm elements,neither of whieh was linked with

what Yai’ “T \tfie
Y in the two tested-parts of this plant. The ear of the main stalk of

ryt

plant 6666C-2 had a ratio of kernel types thats suggested that the Spm in
it was not as closely linked with Y as it was in the tiller of this

plant (table 26). Tests of Spm number and location were made fbth

ee)
eo,
4

a 2
the progeny of each of these plants, and those conducted with thas of
plant 6666C-2 will be considered first.

Progeny test 20, figure 2
Nine plants were grown from the variegated Y class of kernels on

Cave Table 26 fon Rrowul pe enter Cor)
the ear produced by the main stalk of plant 6666C~2. All of them
were variegated. A testcross ear was obtained from each. One Spm
was present in 8 of these 9 plants. It was linked with Y in 6 of the
8 plants having one Spm, (table 48), and possibly with Y in another
(plant 6869-8, table 48), but it was not linked with Y in one plant
(plant 6869-2, table 48). In the one remaining plant, 6869-4, two

appeared to be
Spm elements were present, neither of whichxwae linked with Y (table 48).
Lo

afl

The ratio of kernel types on ears produced by the six plants having 1 Spm
way RAW + - iin s

linked with Y was not i fex—ait— ot trem, suggestawe that the

location of Spm in chromosome 6 might not be the same in each of them,

w60b conducted -y Mover
However, no presemy testg that would establish this/with any one of them.
a

Prygtery, Wot a, tae

Eleven plants were grown, from the variegated, Y class of kernels on
the testcross ear produced by plant 6665G-16 (table 24) "under culture
number 6866. Testcross ears were obtained from 9 of these 11 plants.
One Spm was present in the tested parts of 7 of these 9 plants and it
was not linked with Y in any one of them. The cmmbined ratios of kernel

types on the 8 testcross ears obtained from them are given in table 49,
- wy

The tested purt of one plant (6866-2, table 49) had two Spm elements,

“a

neither of which was linked with Y. In the remaining plant cf=tiric
pregens, (plant 6866-5, table 49) 3 Spm elements were present. The s0

eviderce—obteined-fmem tests of the progeny of plant 6665G-16 estattsred
puaed ne tovelisem Breer ofttpun dueuk in ¢ uted wid Spun ca 7
eb —t ttanspesed—Spm—tha-t was not carried in chromosome
Yona Tl ve
6*close enough to show linkage with #.
a ° Progen TH D2, heceer ze.
the progeny of ro Reg bf
Prmgexy fests of/plant 6665G-21 were conducted with 8 plants grown

a from the Y class of colorless, sh, kernels on the self—pollinated ear

of one of its tillers under culture number 6863, and 2xemm with 17 of

the 20 plants in culture 6867 that were derived from the variggated
2 OT nape Trprw iby so a-% |
Y¥ class of kernels on the ear entered in table 24. In culture 6863,
Wet ero Can podualy
the kernel types-on—+the—test=cress—ean—produced—by one plant that was

tt
Y/Y gave no evidence of the presence of Spm in the—tested—part—of_this
158

five other plants in this culture had one Spm element. Four of them
were Y/y, but in none of eheee plants was evidence given of linkage of
Spm with either of these alleles (table 50). The ratio of kernel types
on the test cross ear produced by two other plants, voth of which were
Y/yy suggested that in each of them an Spm element was carried at the
same location in each member of an homologous patr.(plants 6863-3 and
6863-9, table 50).

Of the 17 plants derived from kernels on the testcross ear of this
same plant, 6665G-21, 16 had one “pm. Clearly, it was not linked with

ib pao

Y in 15 of thém (table $0) nor with Pr or Wx,which could be determined
at the same time on te testcross earf, of-these—plants. In one of these
16 plants, howevey, the single Spm in it Ydelbe, was carried in the Y
bearing chromosome 6, as the ratio of kernel types on its testcross ear
suggests (plant 6867-9, table 50) AY Thus, the tests of the progeny of
plant 6665G-21 conform with tht which could be expected if the Spm

wpa

element in it was not carried in chromosome 6 at a position that would
rita by sryrernumey

give evi G-uce == linkage with Y. In the one plant in which Spm appegard

to be linked with Y, a successive transposition o®= 5 could have returned

it to a location in chromosome 6 that Would express lirkage with Y.

'Two Spm elements were present in the remaining plant (plant6867-18,

tahle 50) neither of which was linked with Y nor with Pr or wrx.
159

Progeny test 23, figure 2

 

The kernel types on each of the two testcross ears of plant

of 2 Spm elements
6665E-19 indicated tha® presence/in both tested parts of/this plant.

Neither Spm was linked with Y (see table 26 for kernel types on tajfch
of these two ears). “ifteen plants were grown from the + cAlss of
vareigated kernels on the ear produced by the main stalk of this plant.

One testcross esr was obtained from each of these 15 plants. In one

bodk We obtlerewe The Want dude
plant, the kernels on +e® testcross ear gave no evidence of the presence
A

Of Spm | itiedslace-paeees . In 11 plants, one Spm was present and it was not
linked with Y (plants in culture 6864, table 51), nor with Pr or Wx.
Two plants had 2 Spm elements. +n one of them, no evidence was given

of linkage of am Spm with Y (plant6864-7, table 51). 4n other other,
Wg VAIO 4 Pned Tym avccorty
however, link:ge of one Spm with Y was—prebebte (plant 6864-3).
table 51
In one plant (6864-12) 2 or mere-probabty 3 Spm elements were present

adn the ratio of kernel types on this ear suggests th:t one of them

aut

may have been carried in the y bearing chromosome 6. vai 4 derived
from the Y, variegated class of kernels on the testcross ear of the

tiller of plant 6665E-10 carried Spm. One Spm was garrxea# present in
12 of them and it was not linked with Y (plants in 6865, table 51) nor

with Pr or Wx. Two plant (6865-1 and 6865-12, table 51) had two

Spm elements, neith r of which was linked with Y nor with Pr or Wx;
160
Two exceptionsl plants appeared among the 28 in the progeny of
plant 6665E-10 that were examined. In each of them, at least 2 Spm
elements were present in the tested part of theplant. In one plant,
one of these appeared to be located in its Y bearing chromosome 6.
In the other, one Spm appeared to be carried in the y bearing chromosome 6.
No progeny tests were conducted to establish the location of Spm in
either plant. Since only one testcross ear was obtained from each
plant, the constitution of Spm in other parts of these two plants is not
known. However, an early occurring transposition of Spm may have been
responsible for insertion of an Spm element into the y bearing chromosome
6 in plant 6864-12. This chromosome, contributed by the tester stock
plone ridin o Caer ys oatly

Op
did not have Spm in it. is  ianenidanip-neyorer, Foom the test@igr Zor»

an active
entered in table 51, that plant 6665E-10 did not carry/Spm in its Y

bearing chromosome 6.

Progeny test 24, figure 2

 

PAO
The ratio of kernel types on) thé three testcross e:.rs produced by

plant 6629B-5 is entered in table 8. This plant was y/y, Pr/pr, Wx/wx
in constitution. From the ratio of pale to variegated kernels on these
ears, it could be suspected th.t this plant had two Spm elements, both

of which resided in one chromosome of the complement. The pollen parent
161

th:t had been used in making the cross with the first ear on the main
stalk and with the tiller ear had been homozygous for as» sho, y, Wx, and
Pr. That used in making the cross with the second ear on the main

stalk had the same constitution except that it was homozygous for pr.

mo hau yng arise val rusaowe S aordr pry,

gud s

&

Although this ear had only a few kernels on it, the ratio of, tyes among 3

them suggested that Spm ‘in plant 6629B-5 was inked ri thf . Kernels >
A

Y

were selected from each of the three ears of this plant and sown in the Ss
bbb St bOFS Os >
summer of 1954 under culture numbers,indicated in table 18, From the a

Kory Lpurure, ALyLre? Aipfoseel ps0 yh > &

second ear on the main stalk, $ plants were grown from *

Jur ielins thal wl thane Calley 2
Chass of kernels and 3 were Speen EDO peel variegated, Sho, Pry CtLess—oft

WE, Bolin, " ‘Leow bua ned" vot ented To Pa Ottab 2 Pan

 
 

A GW
was carried in chromosome 5 in the parent plant, anherge-nubes=of test

crosses were conducted with the plants in cultures 668% to 6685.
AcsutUA & tu enced
The kernel types on the | {ears produscd ty these testeseases cotolisned
ho Qaaunggt urn oy < ¥6-4B-5,

the presence of two Spm elements in the parent Plent, each of which was
its with pr
located in/chromosome 5/and at positions that allowed linkege to be
ts markn. di fh:2gue val
expressed with the-gikekewxefxgrxe—pr. By reason of the constitution J
Qin nnrbor ty Ged aN) % tone oy plant 6627 b-5

ef ef the male plantsused in the cross, all plants derived from kennels

la i
on the first ear of the main stalk (BaP Re 6683), and from the ear of the
162

tiller (plants in culture 6685) carried Pr in one chromosome 5. For
the same reason, those derived from the second ear of the main stalk had
pr in one chromosome 5. As stated above, plant 6629B~5 was Pr/pr.
Therefore, the plants in culture 6683 and 6685 could be either Pr/Pr or
Pr/pr, and those in culture 6684 could be either Pr/pr or pr/pr.

Seventeen plants,wexe grown from the variegated, Sh, class of kernels,
od p that
uit Gn cultures 6683 and 6685.  Sixtern of them were variegated but one/was

Pr/Pr was totally pale pigmented and no evidence of Spm was given by the

kernels on the testcross ear it produced. Among the 16 plants that

were variegated, 4 were Pr/Pr and 12 were Pr/pr. One plant (6683A-2),

derived from a nniformly palecolored kernel, was variegated and it was

Pr/pr. guy
On the testcross ears ed 15 plants among the 35 in cultures 6683 and
6685 that were derived from colorless, sh, kernels, no evidence was
given of the presence of Spm in any kernel. Twelve of these 13 plants
were Pr/Pr and 1 was Pr/pr. Homexex, Ain active Spm was present in 20
of these 35 plants. Four of them were Pr/Pr and 16 were Rr/pr.
In the 2 remaining plants, each of which was Pr/pr, Spm was present but
it was in its inactive state in most of the Spm carrying kernels on the
testcross ear Seach
The three plants in culture 6684 that were derived from variegated,
Sho, Pr kernels on the second ear of the main stalk of plant 6629B-5,

were, as excected, Pr/pr. Among the 14 examined plants derived from

the colorless, sh, kernels on this ear, no evidence of ‘pm was given by
163

any kernel on the testcross ear produced by 3 of them, each of which was
Pr/pr. The other 11 plants had Spm. Two of these plants were Pr/pr and
9 were pr/pr.

From the distribution of Spm and @ the alleles of Pr te the progeny
of plant 6629B-5, it is evident that Spm was carried in the chromosome

the “pm carrying

with pr in all three tested parts of this plant. Because/kkm progeny
of plant 6629B-5 could be distributed to 11 distinct classes with (ecoreling

: y CORT Whew wth apg at To
Fespect to the, alleles of Pr & to Spm, charts were constructed to
indicate the class into which each plant, or part of a plant, could be
placed. For theplants in culture 6683 and 6685, this is given in figure 3
and for the plants in culture 6684 this is given in figure 4. In
tableg 52 is entered the kernel types appearing on the testcross ears of
the Pr/Pr plants in the first Wo asses given in figure 3. In table 53
is given the kernel types on the test cross ears of the If ciasses of
plants¥ that were Pr/pr in figure 3. Because of the simil.rities in ratios
of kernel types on each of the ears produced by plants in the first 4
classes given in figure 3, tha data from all ears are entered in summary
form in tables 52 and 53, The ratio of kernel types on all ears produced
by plants in ciass 6 of figure 3 were not alike. therefore, the phenotypes

of kernels on ears produced by each plant are entered sepurately in table

53. On most of these ears, the percent of recombinants among the

QUOi.g beuk 25,
variegated class of kernels was similar, 1 i foiennedi,

|, Meviation from this was expressed by the ratio of kernel types appearing on

the ear produced by the tiller of plant 6683D-2. In this plant, changes
164
pour doehgne'®
in Spm were occurring as evidenced by the appearance of a sector on this

ear in which all of the kernels were pale pigmented and by the fact that

the Spm constitution of the tiller differed from that of the main stalk,

Bho Latton.

‘,

a

whieh was Pr + +/pr Spm Spm. The Spm in the tiller probably had been
transposed to a location close to pr, as will be shown shortly. A marked

~ wae por eeate Mowbueut
difterencéjrad a1s¢) expressed on the ear of plant 6683D-3 but on this ear,

there—-wes—e—nerked<deficieneyenien the number of kernels wien the pr
phenotypewy wud Loven, Wen LA pudid ‘

The kernel types appearing on the testcross ears produced by the Spm

teem dwusto
carrying plants in culture 6684 are entered in table ot under the

Combtuling ood a1 chown

headings—eiven in figure 4. A number of testsrosses were conducted

with one plant,6684D~1, which was Pr Spm/pr +. The percent of recombinants
. . OU

among the variegated class of kernels on the ear of this plant, and fem

those produced by use of the pollen of its tiller is approximately 34.

The pollen derived from the main stalk of this plant had many grains in

which Spm was absent, as the ratio of the pale to the variegated class of

kernels on testcross ears produced by use of it indicate. Tests of the

progeny of plant 6684D-1, derived both from the selfpollinated ear of the

tiller and of the pollen of this tiller indicate that the Spm in its Pr

chromesome Cowlel huawe
/probebly

resulted from crossing over rather than transposition. The
percent recombinants appearing on the testcross ears of its Pr Spm/pr+
progeny amounted to approximately 25, as will be shown shortly.

From the above described tests of the progeny of plant 6629B-5,
165

its constitution would appear to be Pr + +/pr “pm Spm. Relatively

little transposition of the Spm elements in it occurred during development
of this plant and during development of its “pm carrying progeny when this
is compared with that which occurred in some of the plants previously
discussed. On the ear of the tiller of this plant, a few kernels appeared
that exhibited only one to several small dotw of the Ay type pigment

in a colorless background instead of the expected pattern of many such.

m-l

spots usually produced by either state 5719A-1 or state 5718 of ay

when Spm is present. A few kernels of this type likewise appeared on
ears of some of the plants in its progeny that were derived from fully

variegated kernels. Tests conducted with plants derived ffom smeh
woth Gfkorsd norrecaduon paffe wo

Kernels showed that the Spm in them was behaving in a different manner.
Also, one of the Spm elements in plant 6629B—5 entered the inactive
phise in some cells. For this reason, some plants that were derived
from the pale class of kernels on the ears of plant 6629B-5 had an

Spm element in them. Return to the active phase in some cells of these

WallowlA be tated, Lpwow., Cert wownily, pLeuity Wired pn pats Rarrncl ap uch lane Span ve Witen

Slants occurred, bul only very late in development.’ These two types of

Aust nmiadh oot ATlouLinr 0

change in Spm action will be considered subsequently. They—are-
1A

dawn Vorbeuw of change in action of Spm

mentioned hcre because initial investigations/were conductéd with plants

in the progeny of plant 6629B—5.
166

Progeny Test 25, figure 2

The ratio of k-rnel types on the ear produced by the tiller of
plant 6683D-~2 suggested that the Spm in itjoccuppied a position closer
to pr than in related plants that were Pr +/pr Spm, table 53. In
order to verify this, seven kernels were selected from the variegated, Pr
class on the ear of the tiller and sown under culture number 6878 in
the summer of 1955. The selected kernels were derived from the
recombi::ant class on the ear. As emphasized earlier, if Spm is located
close to a gene marker, the Spm-carrying recombinant class is likely
to be composed mainly of individuals having a newly transposed $pm
element in them. This proved to be true in this case. In 6 of the
7 tested individuals in this class, the Spm in them certainly had been
transposed from a position close to pr to another location in the chromo-
some complement, as the kernel types on the testcross ears obtained from
each indic:ite, table 55. In one plant, 6878A-1, Spm was carried in its
chromosome 5 with Pr. The location of Spm with respect to Fr could not
be estimated from the ratio of kernel types on the testcross ears it
produced because of the preponderance of the pale class of kernels on
each. This indicated, nevertheless, that the Spm in this plant had

undergone change in a number of cells late in plant development.
167

In the 6 plants having Spm at a new location, no linkage of it
with Wx was expressed on the testcross ears produced by any one of these
plants. Neither was it linked with’¥ in plant$ 6878A-3 or 6878A-4 in
which this could have been detected. The Spm in plant 68%8B-3
underwent early occurring transposition, as indicated by the difference in
Spm constitution in the main stalk and in the tiller of this plant.
Because at least 6 of the 7 individuals that were dérived from the
recombinant class in the progeny of the tiller of plant 6683D~2 had a
newly transposed Spm element in it, it is concluded that the Spm in theo

tiller of-plant—eee3i-2 was located very close to pr.
168

Progeny Test 26, figure 2
A similar type of test to that just described was conducted with
recombinant»
plants derived ffom thd wariegated\ class ef/kernels on an ear produced by
plant 6685F-3. This plant was Pr +/pr Spm jas the kernel typew appearing
on three of its testcross ears indicate, t:ble 53. The location of Spm
the tiller of
in this plant did not appear to be as close to pr as it was in/plant
6683D-2, just described. It could be anticipated, then, that a larger
propprtion of individuals in the recombinant class would represent cases
in which crossing over between the site of insertion of Spm in chromosome 5
and the locus of pr was responsible for their appearance in this class
rather than cases of transposition of it to a new location in the
chromosome complement. This appears to be confirmed from tests conducted
with variegated plants derived from the recombinant class on the ear of
a tiller of plant 6685F-3. The kernel types thut appe red on this ear
Voveetid
are shown in line 1 of table 56. Ten kernels were selected from the 21
A

that were veriegeted-amd Pr in phenotype, and sown under culture number
6882 in the summer of 1955. Spm was present in 9 of theg¢ 10 plants
derived from these kernels but no evidence of its presence was given by

OVC Spun wor pnd TY;
one plant. An 8 of the 9 plants having “pm, *—Spe—was—pmesens and it

A $ eu

was linked with fr in four of theme, as shown in lines 2 to 5 of table 56.
169

In the other four plants, Spm was not linked with Pr (lines 6 to 10,
table 56) nor with Wx which also could have been expressed on these ears.
In one plant, 6882A-2, at least 4 Spm elements were present (lines 10 and
ll, table 56).

The percent of recombinants among the variegated class of kernels is
given in round numbers in the last column of table 56. Although
difference in this on the different ears is to be expected because of
transposition of Spm that certainly occurred in some cells of these
plants, deviation from that expressed on the ears of the parent plant
is not great enough in any one case to indicate with certainty that the
location of Spm in chromosome 5 in any one of them differs from that in
the parent plant. Only progeny tests of each would allow this to be
determined and these were not conducted. However, the Spm element in
at least 5 of the 9 plants derived from the recombinant class on the parent
ear had been transposed from a location in chromosome 6 that gives linkage
with pr to a new location in the chromosome complement.

Progeny Test 27, figure 2

Among the examined progeny of the tiller of plant 6629B-5 there were
3 Pr/Pr plants in which 1 Spm was present (figure 3 and table 52).

Among them was plant 6685G-2, With respect to chromosome 3 constitution,

= - . thi lant
this plant was a” 1 (state 5719A-1) Sh,/ a, sh, An ear of this plan
169a

had been used in a cross with a plant that was homozygous for state
571L9A~1 amt and for Sho,» pr, y, and wx and in which no Spm was present.
The kernel types that appeared on this ear are entered in the first

line of table 57. Variegated
170

kernels were selected from this ear and sown under culture number 6875
vy
Gaping the summer of 1955. The 20 plants derived from them were
examined for the Spm constitution in each. The pollen used in making
the testcross with each was obtained from piants th t were homozygous
m-1 and
for state 5718 ay ,/for Sos pr, Y, and wx, and in which no Spm was
present. The test had been devised for reasons other than to determine
if Spm was located in chromosome 5 and for the desired purposeg¢, use of
Neyer Whan,

pollen from the described tester stock was most suitable. from thes2
AN

tests it was learned,hewever, that the Spm in plant 6685G-—2 was located

in chromosome 5. With regard to am constitutions the plants in
culture 6875 were of two types: homozygous for state 5719A-1 amt and
dag WN ontlend ae
heterozygous for this state, with ay being carried in eee ocous
A
chromosomes 3. The Pr and pr phenotypes among the pale class of kernels

ror cout
on ears of plants that were homozygous for state 5719A-1 be

distinguished readily. However, on the ears produced by the heterozygous

m-1

plants, only half of the kernels would have state 5719A-1 ay

in them.

The other half would receive a, from the female parent and state 5718
m-1 K . m-1l

ay from the male parent. ernels having state 5718 ay and no

Spm are only very faintly pigmented. Distinction between those that are

purple (Pr) and those that are red (pr) is made only with considerable
171

effort and this was not attempted in classifying the kernel types on
ears produced by plants in culture 6875 that were an /a, in constitution.
For this reason, all kernels in the pale classes on the testcross ears
of plants of this constitution are entered in tavle 57 under the heading
"Pale", no distinctions being made between those that were Pr and those
that were pr.
20

Spm in its active state was present in 17 of the/tested pl nts in
culture 6875. In three plants, however, although Spm was present, it
was totally inactive in most parts of each plant and in most of the

kernels having it on the ear each plant produced. One “pm was present

in all tested parts of 15 of the 17 plants having an active “pm and it

“

4

was carried in the chromosome, with Pr in 14 of them, as the kernel types
on the ears each produced indicate, table 57. The single Spm in one
plant was not linked with Pr (*lant B-8, table 57). In two plants,

2 Spm elements were present, one of which was linked with Fr Plant B-9,
and ear on main stalk of plant B-~7$. However, the tiller of plant

6875B-7 had only 1 Spm and it was linked with Pr. gowns
Prorat Wap Oko she
In this progeny test, no selection was made for’ aaa location or
w We plano
constitution of “pm. from the fact that the large proportion of prezeny
A

plants carried Spm in chrmmosome 5 and at a location that gave otew
A
172

clexr evidence of linkage of it with Pr, it may be concluded that the

pow

Spm in whee plant did not undergo frequent transposition during develop-
ment.
Progeny Test 28, figure 2
Tests of the three plants in culture 6684 that were derived from

the recombinant class of variegated kernels on the second er of the

of plant 6629B-5
main stalk showed that plant 6684D-1 was Pr Spm/pr + in constitution
(figure 4 and table 544. A number of testcrosses were conducted with
this plant, including use of its pollen for this purpose. Pollen from its
tiller had been placed on the silks of plants that were homozygous for
state 5719A-1 amt and for pr and in which no “pm was present, and also

silks of
on the/ears of some plants that were homozygous for ay and for pr and in
which no “pm was present. Variegated kernels in the Pr class were
selected from an ear produced by the former type of cross and grown
under culture number 6880, and selection of kernels of a similar type
from an ear produced by the latter cross werexgxrmwn were sown under
culture number 6881. Among the 11 plants in culture 6880, 10 were
variegated but one plant was uniformly pale pigmented and no evidence of

the presence of “pm in it was given by kernels on its testcross ear.

All 10 plants in culture 6881 were vuriegated. An ear of each plant
173

m-1

was used in a cross with a plant homozygous for state 5719A-1 ay

and for Shy, pr, y and wx and in which no “pm was present. xxx The
in culture 6880

phenotype in each kermel on the ears of tkesz plants/was readily
classifyable. However, difficulty was encountered in separating some of
the kernels that were pr from those that were Pr in the pale class on the
ears of some of the plants in culture 6881. This was because of a
previously undetected mutant locus that was segregating in the a,/a,
plantg used in making the cross with plant 6684D-1. When present, this
mutant alters the pigment produced in the pale class of kernels that are
homozygous for pr from a light pink to a lavendar shade that is sometimes
quite intense. This mutant does not alter the phenotypic expression of
Aj. The Ay dots in the variegated kernels that are homozygous for pr
are deep red when this mutant is present. Therefore, in considering the
phenotypes of kernels on the testcross ears of plant in culture 6881, given
in table 58, all of those in the pale class are combined under the heading
"Pale",

Of the 20 plants in cultures 6880 and 6881 that had Spm, one Spm
elements was present in 19 of them and its was carried in the chromosome 5

having Pr in 17 of these 19 plants, as shown in table 58. In one plant

3 “pm elements were present (plant6ss1-5, table 58). In the last
L74
column of table 58 is given the percent of kernels among those that were

ov Barn
variegated that were in the recombinant ass the 17 plants in wh ch

Spm was linked with Pr. Although considerable varidation in this was

expressed on different ears, the aver.ge percent sexes greater

than that expressed in the progeny of plant 6685G-2 (table 57), suggesting
that the location of “pm in chromosome 5 in plant 6684D-1 was not the

same as that in plant 6685G-2,

In the progeny derived from use of the pollen of the tiller of plant
6684D-1 there were 3 plants in which transposition of Spm had occurred,
In two of them, 1 Spm was present and it was not linked with Pr in either
plant. in the third plant, at least 3 Spm elements were present. The
appearance of plant with more than 2 Spm elements in them in the progeny
of plants h ving only 1 Spm has been met with on a number of occasiona,
and examples of this were noted in the progeny tests entered in tables
42, 45, 47, 49 and 56.

Tests of the progeny of plant 6684D-1 wasdalso conducted with phants
derived from the variegated tr class of kernels thet appecre on the
earg of the tiller .xkkxtxwas This ear was produced by self-pollination.

The phenotypes of the kernels that appeared on this ear are entered in

the first line of table 59. Of the 16 plants in the progeny derived
175

derived from this ear, 15 carried Spm in them but in one plant, no

evidence was given of the presence in it of Spm. Eleven of the 15
plants having Spm were Pr/pr. In 9 of these 11 plants, one Spm was
in
present and it was carried in the chromosome with Pr/5 of them
(plants under heading Pr Spm/pr + in table 59). It was present in the
chromosome with pr in +m other two; plants (plants under heading Pr+/pr Spm
table 59), but in the remaining tww plants, no evidence was given of its
being carried in chromosome 5. The two other plants that were Pr/pr
(plants 6879-11 and 6879-19) may have had an Spm element in each
chromosome 5. Of the four plants that were Pr/Pr, two had 1 Spm element
the

(plants 6879-6 and 6879-12, table 59) and/two others may have had an Spm
element in each chromosome 5 (plants 6879-1 and 6879-14, table 59) although
the ratio of kernel types appearing on the ear of plant 6879-14 suggests
that it had two Spm elements that were not at allelic positions in an
homologous pair of chromosomes.

The percent of recombinants among the variegated class of kernels
on ears of plants in which Spm was carried in chromosome 5 is given in
round numbers in the last column of table 59. The average of this

is similar to that given by plant 6684D-1 (table 54) and is higher than

that expressed by the progeny of this plant entered in table 58.