LOL The tester plants in part II of table 19 were also used to det-rmine if the uniformly pigmented plants derived from unifor ly pigmented kernels appe ring on ears m=] . / vroduced by crosses of »nlants ccrrying the $720 state of a, (see table ae y 18 for seloections) carried a stable mutant of state S$ee that would not respond to Spmygin any manner. These olancs had A i + state di unenbug va 57204 and Sh, in one chrovosome 3 and ay shy in the homologue. A 7. duel If Spm were also present in them, to which the mutant wes not res-onding, then its presence would be ckeswely revealed by the anpcarance of variegoted al ( state S719A-1),; kernels within the/sho carrving kexmeksxam class on ears produced by 0 neu. crosses with the tester vlanis in part Il of table 19. This tyve of test, A as well as some others that will be described later, indic&ted the stability Aurela OW MAU erty Ay Pat ~_ of the musants derived from state 9720 for some of the plants carrying them A Cas VER also ked Spm, “ The tester nlants in Part III of table 19 weve particularly useful for introducing the Spm element(s) in them into k rnels on ecrs produced ew - by plants thet were derived from pale, Sho keemeis.in table 18, “nis was especially important when the state of a” in them was not 5719Aa-1,. Alun Creat Yaw the wendy ¢ homey ov de Msg Low Dat In all crosses of this type, the state of aw’ carried in the plant being 102 tested would respond to the Spm delivered to the endospe»m by the t-ster plent. Ie the plant being tested was aut (any state but 57T19A-1) Sh>/ a; sh, in constitution, the diffcrence in variegation y VON ual oh slut et He ay pattcrn is the sh, class of kernels when comrred with that in the sh A 2 class was always evident and this was strikinbly so when the plant being B ry aad . shah arto - ore % ‘ Cee _pe rt Ke 5 ve hed pale: *p fatal, if pee ils fay tested had either state 5700A or state 5996-h., This was anothsr test “A thes confirmed the uniaue resvonse of each state of ay to any one Spm. element. It was also important for demonstrating the relation of Mew response of the a5 state in the plant being tested to the particular mM ove plant, Spm constitution in the tester plant.“\ #® ébe Spm wer: linked with a know CANTY 4 gene marker (Y Spm / y + in olant 66668, table 19), the kernels on ears a A OW produced when its pollen was used to make tee cross paeved linkage of wor uuctby pate Coders Urs und ye Wire 2 yiivred the variegated class of Kerne’ Ss” with—tete-meniker dn all ears there the dro aly, constitution “With resseet_te_tadecmsnker the plant being tested weut Aric s bee op ese d asea, “the ratio of va srlegated to pele kernels OT BWA. ‘hes Tes tue ey / fon, a the Shp kKesmeds ani the ay carrying sh, kernets reflected the NA “ number of Som elements that were present in the tester plant (1 Spm cally 4 in plants 66662, 6671, 6673F and 6690 and at lesst 3 in plant 5680D), : A Plants derived from the uniformly pale colored kernels in table 18 ela 103 developed anthocyanin pigment teet wes woaker in intensity than that A rv tig wand produced when AS is present. Among the, plants derived from ths variegated kernels, two distinctly different tyves of pigmented areas Aipa appesred in a non-pigmented background. Cne tape f anthocyanin pigment resembling that which is produced when Ay is present, and the size of these areas in which this »igment was rresent was nearly “if the state of ay™l in the plant was 5718, 5719A-1, 5719A-2 or 5999, but they could be large if the state were 5700A, 5996-l. or the original one, always small, being no more than a short streak, Y The other tre Wes Fad commnsed=ef pigment whose tyne and intensity was that wiich the state of Vth Dolfir wie a produced in the absence of Spm, Teco roas covld be of any size 1 A A , from one that included a large part of a plant to small ones that apr cared as fine streaks, The number and the average size of these areas ina plant was correlated with the number of Spm elements that wore present in it: the higher the numbcor, the fewer were these areas, and the smaller . . ». ,. meal. . produced only by mutation occurring to the ay * in—them, wiereas if one . yay o VON aly Spm were present, the Vernlegeted pattern was a composite of the two A types of pigmented areas, the pale areas and the areas vroduced by mutation Meu - of ay - ty wes learmed later that the pale pirmented ares ap aring — Yeung onc o luo (RW in plants eee Bey Spm numbers = BLOT -heeerse—ef loss of the Spm Lob. from some nuclei during development as a consequence of transposition or fe effectiveness _ ef loss o° its amkiwkkxy as a conseavence of its inactivation, if only AE OPAL cee AL one We one Som were present, either of these events Cgcurine tothe -Sem-etement in rt A & nucleus would result in the ampearance of pale pigment in its vrogeny cells, If two or more Som elements were present in a nucleus, then an event must occur to each of them at one time, or a succession of such “vents must occur, first tc one Spm element and then to the other, in order thet a nucleus arise in wnich there is no Spm activity. patterng of varieg:tion exhibised both by kernel (see vage 00 ) end by nad Ocala wey cit plant may be strikingly different depending upon the Spm numer, in their arent meme cman mame em . ae ne tee nee oa) 7 — oom, te nuclei, However, this relationship #8 not an absolute cne, fer Qt also - “ \ : depends both upon the time during develovment when these events occur and i the frevuency of their occurrence at any one time, and this is a property of the isolate of “pm present in a kernel or a plant. Spm elerents urnder- go change in stcte thet alter these properties and discussion of this etary nya Will be given in sections devoted to trensposition of Spm and to its aX inactivation, For this reascn, not all kcrnels and plants havins one eee ee Spm element in them may exnibit a high e=8rF pale Vee yore arecs, The Spm element in then may not be subsaak tee frequently ocourring | a“ modification of the tyres deseribed, ee petting et nes 105 DO taxa qe nition oe Discussion of tee tests of Som conducted during the summ ry of 195k. } 4 >}. will commence with progeny of plavts in culture 6529A (table 5) whose - od constitutions were ay 1 (state 5719A-1) Sh, / ay sh, and considered to A th. ee be Y Spm / y +. The silvs of the ears of plants in 6629A had received “Ny pollen from plants of the standard test»r stocks, homozygous for a_, sh wort edied from (roduad < and y. Seleeted Kor nels, @a two of the ens of plants 6629A=1 and plans * hee Tey pte of Aowuls eoloepael Gu of 662GA-7 and kaPone esr of plants 6629A-lL, 6529A-6, and 6529A-9, wewe . an dar nbc WA of DA sou table 183. The vhenotyvpe of some kernels on the ear of the tiller of plant 6629A-7 were aberrant. Plants derived from selected kernels on this esr were grown under culture number 6675, and tasts of them will be considered separately fetlownedisessston—ef Those conducted with \ Ae * hue progeny derived from the five other esrs grown under culture numbers “A 6665, 6666, 6670, 6673 and 667k. In tadle 20 is given the number of ~lants in each of the above five cultures that were derived from ke nels with yellow (¥) or white (y) endosperms among thqpale Sho, the verlegated Shy, and the colorless, sh classes of kernels on the -arcnt ears. In addition, one plant was grown from a variegated, sh5, Y kernel in culture 6666, Four other plants were grown from kernels whose phe©otzpes differed from otuers on the 106 Tarte & olthornuse parent ears, as described in the footnote of table 20. TYhe nature of alongs with Mune the modification r sponsible for them will be cons’dered later KMEN tests tweak wid of other nlants derived from similar t:pes of kornels, mrexdixuruxeedsx Tube 20 , All 61 vlants deriv eg from thgpe ale, Shp class of kernels, were Wan he awe un ll Wut toa cacti than Wat Of joa uate wtzea Ry ” bi a uniformly pigmented and “the type of pi gnen’ Was hie —peocuced mien Spr isabsent. Among the 66 »lants derived from the variegated kernels, all were variegated except one, This exceptional plent was unifornly pigmented anc the type and distribution of :igment was the same as that in plants derived from the pale class of ke nels, Tests conducted with this plant gave no evidence of the presence of Som in it. Tt was learned subsecuently that loss of Spm from a nucleus, either during development of the female gametophyte or during verv early embryo development, will give = een rise to a ke-nel whose endosperm and embryo differ in constitution, and A ases of this will be considered in) the section: devoted to transpositions. , . - y ees lie ag han, Ay got feta oS poe RG oy OLéieLe med ONO LEB Sh tees Tee ete Cte he party _ Ou ale Ae hom an Ht Sued theft De Ce Te MEF C "hea, Qo Audie | ‘at Ayglieat ae wtb ey : oti, fesse conducted with kke plants entered in table 20 were both me VUE TTN 4 roa numerous and varied in type, Crosses were made with plants having the following constitutions: the standerd tester atocks, homozygous for ay andé the Cale eduer AW AA els sho, / three different tees of dele olants whose constitutions are ay given in table 19, and with other plants he ving states of a not oe a lab Lp 107 4 Shee fra . , ak Jaye ye RL entered in table 19, The tesis. conducted with each plant will not be hove a bee ! listed but in order to illustrate the scope of sueh tests, those ecnducted “ ty ist Fahy dio died Se that | Sup ebacsrs we to with each ef+tse plantg in cultures 6665 and 6666 are given in tables el and fe aes A feed aaeny oy ny Poe: ily bert A A hgemes ° 226 As indicated previously, these-piants-were-derived from-setect-d 4 kernels.on the main esr and on the tiller ear o? vlant 5629A-1 (see table BE 5 for kernel types on each of- these ears). Ineluding the many ears obtaine from crosses conducted with plant 6666@, whose constitution is given in table 19, over 1%0 ears were produced from test crosses conducted with the Ghel mul 6666 plants in these twe cultures, Because transposition of Yom may occur in A scme cells during development of a plant, and result in loss of Spm or in change in its number in some somatic nuclei, the ko-nel types on each ged os ear am the ratio of types had to be considsred with this possibility in mind. severtheless, on many ears produced by one type of test-cross, both the phenotyves of kernels and the ratios of these were often much “AN we Ualy.n0 uk alike, Thevefore, data obtained from such ears many be summed, On gome ears, however, the ratio of phenotypes did not agree with that given by the majority of ears and the cases where this was nected will be Wore ow. £4 yt ning indicated ss deviation often proved to be of considerable significance Lunthinprg Om Wan ib My Youn dling #. “Lp of Ceres tis a There were two objectives for making the test-crosses entered in A 108 parts I and II of table m1, One was to establish whether or not Spm were present ina plant and the second was to detcrmine if the a in the plants not having Sym would-be capable of responding to it. If Spm were absent, no vericgated kernels should apoear on any of the eight ears produced by the test-ceross wits the standard stogck that wes g& I ° the first line of homozygous for a, and sho, and as shown in sokwmax?xaf table 23, none anpe red. Also, if these plants are crossed by plants of tester type I or II, table 19, no vi riegated kernels shoulg anpesr on any of the resultine ears, and as lines 2 and h of table 23 Indi CEEe:s none asveared, towever, if tester plants of tyre III, table 19, are used in cross - necessary to examine its location in individual plants in the progeny x ra _. f Pa YG Po mer RAL raf ALOHA of those in which its number and location was known. This had been .? determined fer-—Spm in some of the plants of culture 6629 (table 5 and ane 4 8). Therefore, e tests of the progeny of some—of the plants in Wiiag wmlervolhin. for hus pier. pore - this-cutture was conducted during the summer of Lg suf Those conducted } with the progeny of four of the Y Spm / y + plants in culture 6629 were discussed in the preceeding section. “ At was shown there that in the AY majority of, , Spm carruong Brogeny, phents, onély 1 Spm was present,and op f ‘i sank Ue 4 that ad the Y / y plants, it was carried in chromosome 6 with Y and at A the same location, or certainly close to this, as in the parent plants. 123 prog In a Tew plants, however, Spm was not linked with the Y marker, and in Owe ¢ wads (Uy Leicltie wit wane pool, A wetey Lied werk wn otlaar plercite several of them, two Spm elements were present instead of One y 4 Some of vw wrtrabid dud Vy purge ol MoeTlow Wee the cases PO een was found were Le coun dod “Guay, of Mess of the examined plants, whose -oone+i-tutions—were-comsidered in—the—Lastsection were derived from kernels on the testcross ears of wu cube 66297, a plants. entered in table 5. In addition, an ear of the tiller of one of them, plant 6629A~4 that was Y Spm/y + in constitution, had been self-pollinated. Plants derived from selected kernels on this war were chow tat caucel boct examined for the Spm constitution in each. In‘ tae Y and Spm carrying WUD Adopt Tote allidtsd 4 aed To Spun ptanis, the following constitutions @ould be expected to appear: (1) ¥ Spm/Y Spm, (2) Y Spm/y Spm, (3) Y Spm/ Y +, (4) Y¥ Spm/y +, and (5) ¥ +/ y Spm. Among the 18 examined progeny plants having both Y and Spm, 3 had constitution (1), 1 had constitution (2), 3 had constitution (3), 7 had constitution (4), and 1 had constitution (5). In the remaining 3 plants, other constitutions were found. All were Y/y. One plant had two Spm elements, neither of which was linked with an allele of Y. Another had two Spm elements, one of which was linked with Y. The third plant had one Spm but it was not linked with either Yor y. If no changes in location or in action of Spm occur in plants having two Spm elene(\ts at allelic positions in an homologous pair of chromosomes, 124 then all gametes each plant produces should carry Spm. On the testcross ears of these plants, all kernels would exhibit variegation. However, changes do occur and the extent of this may be judged by the proportion of pale colored kernels that are randomly distributed over the ears they produce. In the Spm/Spm plants, mentioned above, between 10 and 15 percent of the kernels on the testcross ears they produced were uniformly pale colored instead of being variegated. These kernels represent casew in which Spm had been altered, either in location or in action in cells ~ of the parent plant. qank Po \U4 oO w & Examination of the progeny of individual plants of culture 6629 (Aor Lodr , reread owthe ager confirmed the Spm constitutions that had been presumed | aS kernel precy types appearing on the testcross ears each produced. However, more wes an hounds wee offauud Learned—aboutthis from tests conducted with their progeny, and this is summarized in table 30. Spm apparently occupied the same position in chromosome 6 in each of the 4 Y Spm/y + plants ( A-l, A-4, A-6, and A~7) dyes whose ¥rogeny were examined. At this location Spm undergoes geome change “A both in location and in type of action, and cases_of—+thie—weremontioned Aut . 4) PB © inthe last section of this report, — However, the frequency of cecurmence vn Ue purges opptors who Spur of this is much less than that which occune—te-Spm_when—it occuppies other A loc&tions in the chromosome complement, and Evidence of this will be QUAtanr discussed shortly. Le4a The types of testcross conducted with plants grown in the summer of 1954, whose origins are given in table 18, were described in the previous section. “ome of them were made to investigat®@ the behavior of different states of a," whereas others were made to determine pm constitutions in the progeny of plants whose “pm constitution had been det=rmined. During the summer of 1955, many testcrosses were conductdd for the purpose of intestigating transposition of pm. This reosuired determining the presence or absence of Spm in each kernel on an ear produced by a plant whose 5pm constitution xk was gesixedxto be determined. ae that give For this purpose, it was neceasary to use states of a very feu cle rly defined patterns of mutant spots in the presence of Spm. Therefore, the tester stocks that were used in the summer of 1955 were homozygous for either state 5718 or for state 5719A-1. With each, small spots of the Ay type pigment appear in a colorless background when Spm is present. In the absence of “pm, state 5718 gives only very faintly pigmented kernels. For tests requiring distinctions between (wo Sew) the Pr and pr phenotypes in the pale class of kernels Bester stocks carrying state 5719A-1 usually were used. This was done because kernels in the absence of Spm, the intensity of pigment in tkmxpakexeikass is deep enough to allow distinctions to be made between the Pr and pr 124b phenotypes. With state 5718, such distinctions are difficult because of the faintness of pigment in them. The state of a7 in the plants tested was either 5719A-1 or 5718 unless otherwise stated. The use of these states was important because the frequency of occurrence of gemminal mutation is very low for each. However, occasionally a sector will appear on an ear of a plant hayjng state 5719A-1 in which all of the kernels within it eshibit the same mutant phenotype, indicating that a mutation to or toward A, had occurred in a cell during development and that its progeny cells were included in a sector on the ear. Such sectors on ears appear only very rarely. In the tables given in this part of the report, kernels having germinal mutations were not included. This was done to allow the data to be presented in a simple form whereby the ratio of the pale class of kernels (no 5pm) to the variegated class (Spm present) may be read rapidly. fo be meaningful, inclusion of germinal mutations m—-l in these tables would also require reference to the state of ay that was present in each plant, to whether or not it was homozygous for this state or heterozygous with a, or whether state 57194-§ was present in 1) few kernels with a one chromosome 3 and state 5718 in the homologue. Since/ germinal eiond tx ie tow -£ = Late, l24e mutation appeared on the testcross ears, it was considered needless to complication the presentation, both in the text and in the tables) by detailed reference to the constitution of each plant with regard to the state of amt it carried. In the discussion that follows, the term "testcross" will be used frequently. Unless otherwise state, it will refer to a cross made with a plant whose Spm constitution is to be determined by one that is homozygous for state 5718 or state 5719A-1 of am, for Sho, and for pr, y, and wx, and in which no Spm is present. The number of progeny tests that were made for the purpose of examining Spm constitution in COAT saree. +n describing each of these tests it will be necessary to refer to culture numbers under which ashe different progenies were gpown, and to plant numbers within a culture. To lessen confusion that could arise from use of such numbers in the text, a chart was prepared, figure 2, that gives the culture number of the plant whose progeny was tested, the constitution of this plant, and the culture number of its progeny along with the table number that illustrates the Spm constitution in the plants of its progeny. Culture numbers of plant grown in the summer of 1954 are entered in table 18. They run from 6638 to 6706. The culture numbers for the summer of 1955 run from 124d 6861 to 6900. Those for the summer of 1956, given in this section, are few, being 7260, 7261, and 7285. Those for the summer of 1957 given in this section likewise are few. They run from 7330 to 7334. Another point should be made clear at this time. In casidering Spm number in a plant, it must be stated that it is not possible to distinguish the presence of two or more ~pm elements when these are located very close to one another in a chromosome. “nerease in dose of Spm does not effect change in mutation pattern given by the states of an that have been isolated. The same patt-rn of this appears when either one or more Spm elements are present. One state of a m—1 allows 2 the different doses of Spm to be distinguished from each other but a m-1 1 e state of this type was not isolated early in the study of a Therefore, in this section, when a plant is stated to have one Spm, this does not exclude the possibility that two or more “pm elements were present in one of its chromosomes but located so close to each other tg that detection of this could not be made. The inheritance pattern among the kernels on a testcross ear wo.ld be that of one Spm at one particular &pcation in the chromosome comolement. 1246 At times, mention will be made of sectors appearing on some ears in which no Spm activity is given by any of the kernels within the sector. “ometimes the boundaries of the sectors were cle-rly defined and it was poss®ble to kmawxgmx isolate all kernels within it. With others, the kernel types on the pear would not allow the exact boundart#s to be determined. However, experience with the forms of sectors appear- ing on ears allows one to project the boundaries of those sectors that are not accurately defined by kernel phenotype. When such appeared, the se boundar¥es wase drawn an ear Bar by projectiong and the kernels within nonaead the sector removed from the ear and) souneed separately. Undoubtedly, QR some errurs were made in projecting the boundaries but the degree of _ in this could not have been great. +nelusion/or exclusion/ot a few kernels seriously | dad war Prout from the sector Would not/alter the ratio of kernel types on the rest of the ear. 125 As indicated in table 30, the two Spm elements in plant A-8, and two of the four “pm elements in plaht A-2, occupied positions in the Y bearing 6 chromosome/in each, Evidence of this, derived from tests conductd with the progeny of plant A-8, will be summarized. Progeny Test 2, figure 2 Bhe testcross ear of plant 6629A-8 had the kernel types entered in table 5. The Spm constitution of 19 plants derived from the variegated Y class of kernels on this ear was determined in the manner described in the previous section. Eleven of these plants were YX Spm/y + in constitution. The other 8 plants had at least 2 Spm elements, each carried in the Y bearing chro:iosome 6. The constitution of these plants will be symbolized as Y Spm Spm/y + +, Eleven plants derived from the Y class of colorless, sh, kernels also were examined. Spm was absent from one of them but present in the other 10 plants. In 5 of thee@ket+er 10 plants, one Spm was present and it was carried in the YL bearing chromosome 6 in each (Y Spm/y +). In the other 5 plants, more than one Spm was present and in all plants, each of them was located in the 1 bearing chromosome 6 (Y Spm Spm/y + +). In addition, thtrteen plants derived from ‘the y class of colorless, sh, kernels were examined. In 9 of them, no Spm was present. One Spm was present in 3 of the 4 plants having it (line 7, table 31) and two Spm elements were present in the fourth plant (line 8,