Currently, no information is available comparing the agronomic performance of A1 and A3 cytoplasms in sorghum x sudangrass [Sorghumbi color (L.) Moench] hybrids. The objectives of this study were to compare the effects of A1 and A3 cytoplasm on the maturity, fertility, height, forage yield, and forage quality of sorghum × sudangrass hybrids. In 1989, pollen from a bulk of eight sudangrass populations was used to pollinate four sorghum lines that had been male-sterilized in both A1 and A3 cytoplasm. Hybrids were grown at the Univ. of Nebraska Field Laboratory Ithaca, NE, in 1990 and 1991, in a split-plot design with inbreds (females) treated as whole plots and cytoplasms treated as subplots. The soil was a Sharpsburg silty clay loam (fine montmorillonitic, mesic Typic Agriudoll). Cytoplasm had no effect on days to 50% anthesis, height, forage yield, in vitro dry matter disappearance (IVDMD) or, crude protein. Seed set under selfing bags( fertility restoration) in A3 hybrids was observed, with interaction among A3 cytoplasm sources and lines

Pedersen, Jeffrey F.

Toy, J. J.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Agronomy & Horticulture -- Faculty Publications Agronomy and Horticulture Department 1997 Notes: Forage Yield, Quality, And Fertility Of Sorghum X Sudan Grass Hybrids In A1 And A3 Cytoplasm Jeffrey F. Pedersen University of Nebraska-Lincoln, jpedersen1@unl.edu J. J. Toy University of Nebraska-Lincoln, John.Toy@ars.usda.gov Follow this and additional works at: https://digitalcommons.unl.edu/agronomyfacpub  Part of the Agricultural Science Commons, Agriculture Commons, Agronomy and Crop Sciences Commons, Botany Commons, Horticulture Commons, Other Plant Sciences Commons, and the Plant Biology Commons Pedersen, Jeffrey F. and Toy, J. J., "Notes: Forage Yield, Quality, And Fertility Of Sorghum X Sudan Grass Hybrids In A1 And A3 Cytoplasm" (1997). Agronomy & Horticulture -- Faculty Publications. 957. https://digitalcommons.unl.edu/agronomyfacpub/957 This Article is brought to you for free and open access by the Agronomy and Horticulture Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Agronomy & Horticulture -- Faculty Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. NOTESFORAGE YIELD, QUALITY,AND FERTILITY OF SORGHUM xSUDAN GRASS HYBRIDS IN A1AND A3 CYTOPLASMJ. F. PEDERSEN* AND J. J. TOYAbstractCurrently, no information is available comparing the agronomicperformance of A1 and A3 cytoplasms in sorghum x sudangrass[Sorghum bicolor (L.) Moench] hybrids. The objectives of this studywere to compare the effects of A1 and A3 cytoplasm on the maturity,fertility, height, forage yield, and forage quality of sorghum × su-dangrass hybrids. In 1989, pollen from a bulk of eight sudangrasspopulations was used to pollinate four sorghum lines that had beenmale-sterilized in both A1 and A3 cytoplasm. Hybrids were grownat the Univ. of Nebraska Field Laboratory, Ithaca, NE, in 1990 and1991, in a split-plot design with inbreds (females) treated as wholeplots and cytoplasms treated as subplots. The soil was a Sharpsburgsilty clay loam (fine montmorillonitic, mesic Typic Agriudoll). Cyto-plasm had no effect on days to 50% anthesis, height, forage yield, invitro dry matter disappearance (IVDMD), or crude protein. Seed setunder selfing bags (fertility restoration) in A3 hybrids was observed,with interaction among A3 cytoplasm sources and lines.SORGHUM X SUDANGRASS hybrids provide valuable for-age for livestock consumption and ground coverover a broad geographic region. Important attributes ofthese hybrids include rapid growth, heat and droughttolerance, and high yield. With the discovery of A1cytoplasmic male-sterility (Stephens and Holland,1954), a method became available to produce largequantities of hybrid seed on grain sorghum females witha minimal amount of effort. Commercial productionof sorghum × sudangrass hybrid seed is estimated at45 400 000 kg annually (Kalton, 1989).Several sorghum lines male-sterilized in an alternatecytoplasm, A3, have been available since the early 1990s(Atkins, 1990; Schertz et al., 1990). Grain sorghum hy-brids produced by topcrossing 18 different lines ontoone of these A3 lines were all male-sterile (Lee et al.,1992). Currently, no information is available comparingthe agronomic performance and quality of A1 and A3sorghum × sudangrass hybrids. A3 sorghum × su-dangrass hybrids should be expected to be male-sterile.If grown in isolation, such male-sterile hybrids wouldnot set seed, possibly resulting in high forage qualityJ.F. Pedersen and J.J. Toy, USDA, ARS, NPA Wheat Sorghum andForage Research, Dep. of Agronomy, Univ. of Nebraska-Lincoln,Lincoln, NE 68583-0937. Joint contribution of the USDA-ARS andthe Nebraska Agric. Exp. Stn. Published as Paper no. 11756, JournalSer., Nebraska Agric. Exp. Stn. Received 16 Dec. 1996. *Correspond-ing author (Email: agro137@unl.edu).Published in Crop Sci. 37:1973-1975 (1997).by eliminating seed production. Additionally, A3 male-sterilization of sorghum lines used as pollinators (fertil-ity restorers) in A1 hybrid production systems wouldprovide an entirely new heterotic gene pool for sor-hum × sudangrass hybrid production. Recently, we re-leased 18 combine height grain sorghum lines sterilizedin A3 (Pedersen et al., 1997) and 29 forage sorghumcultivars male-sterilized in A3 cytoplasm (Pedersen andToy, 1997). These new genetic resources could providesome practical benefits for grain sorghum seedsmen aswell as forage producers.The objective of this study was to compare the effectsof A1 and A3 cytoplasms on the maturity, fertility, stat-ure, forage yield, and forage quality of sorghum × su-dangrass hybrids.Materials and MethodsIn 1989, pollen from a bulk of eight sudangrass populations(NP22, NP23, NP25, NP28, NP29, NP30, NP31, and NP35)was used to pollinate four combine-height sorghum lines thathad been male-sterilized in both A1 and A3 cytoplasm:A1Martin and A3Tx398 (A3Martin), AiRedbine 58 andA3IA78 (A3Redbine 58), AlWheatland and A3IA79(A3Wheatland), and A1KS24 and A3IAS0 (A3KS24) (Atkins,1990; Schertz, 1984).Hybrids were planted on 21 May 1990 and 21 May 1991,at the Univ. of Nebraska Field Laboratory, Ithaca, NE, ina split-plot design replicated three times with seed parents(females) treated as whole plots, and cytoplasms treated subplots. Individual plots were two rows 6.5 m long and 0.76m apart. The entire experiment was planted twice to allowcollection of forage yield, quality, maturity, and seed set data.Ammonium nitrate fertilizer was applied prior to plantingat 78 kg N ha-1. Propachlor {2-chloro-N (1-methylethyl)-N-phenylaetamide/Atrazine [6-chloro-Nethyl-N-(1-methyl-ethyl)-l,3,5,-triazine-2.4.-diamine]} was applied at 9.4 L ha-~immediately after planting for weed control. Days to 50%anthesis was recorded every 2 d during the blooming period.Several panicles per row were bagged prior to anthesis andvisually evaluated for percent seed set at maturity. Foragewas harvested after all hybrids had reached the boot stage on19 July 1990 and 26 Sept. 1990, and 16 July 199l and 19 Aug.1991, with an automated plot harvester (Pedersen and Moore,1995) to a stubble height of 10 cm, and weighed. Subsampleswere used to determine dry matter, and for subsequent qual-ity analyses.Subsamples were dried in a forced-air oven at 60°C andground in a Wiley mill (Arthur H. Thomas, Philadelphia, PA),followed by grinding in a Udy cyclone mill (Udy Corp., FortCollins, CO) to pass a l-ram screen. Dry matter yield for eachcutting was calculated as fresh yield × percent dry matter,and total dry matter yield for each year was calculated as thesum of the two individual cuttings each year. In vitro drymatter disappearance was determined as per Marten andBarnes (1980) and crude protein was determined as per AACC(1983). Data were analyzed with the appropriate test termsfor the split-plot design using the general linear models proce-dure of SAS (SAS, 1989). Where significant differences wereAbbreviations: IVDMD, in vitro dry matter disappearance.1973Published November, 19971974 CROP SCIENCE, VOL. 37, NOVEMBER-DECEMBER 1997Table 1. Treatment means for days to 50% anthesis, height, dry matter yield, in vitro dry matter disappearance (IVDMD), and crudeprotein at first and second harvest dates (cuts) of sorghum × sign sudangrass hybrids.Height Dry matter yield Crude proteinDays to 50%Variable Level anthesis Cut 1 Cut 2 Cut 1 Cut 2 Total Cut 1 Cut 2 Cut 1 Cut 2IVDMDLineCytoplasm% -- cm -- -- kg ha -l -- g kg-tMartin 70 174 217 3742 6168 11 582 635 618 126 100Wheatland 76 167 212 3002 5579 9 892 641 603 125 90KS24 72 186 213 3577 5700 10 405 635 606 118 90Redbine 58 69 186 217 3734 6187 11 293 632 592 120 97LSD (P = 0.05) 3 18 nst ns ns 1 671 ns ns ns nsA1 72 177 216 3516 5848 10 760 637 602 122 94A3 72 179 213 3512 5969 10 826 635 607 123 95Contrast (P = 0.05) ns ns ns ns ns ns ns ns ns ns~ ns = not significantly different at P = 0.05.indicated by the F-test, least significant differences (LSD)were calculated. Single degree of freedom comparisons weremade for the two cytoplasms. Single degree of freedom com-parisons were made within lines for cytoplasm effects wheresignificant line × cytoplasm interaction terms were present.Results and DiscussionAlthough year effects were significant for several vari-ables, no year interactions were significant. Therefore,all results were pooled across years.MaturityDifferences among hybrids for days to 50% anthesiswere expected due to known maturity differences in thelines used as seed parents, and were detected (Table 1).Cytoplasm had no effect on days to 50% anthesis, withhybrids in A1 or A3 cytoplasm both averaging 72 d to50% anthesis. Line × cytoplasm interactions were notsignificant for days to 50% anthesis.FertilityDifferences in percent seed set (under selfing bags)among seed parent lines indicate that variability forfertility restoration exists among these hybrids (Table2). Percent seed set (or fertility restoration) by dangrass was greater on average in A1 cytoplasm thanin A3, but no fully male-sterile hybrids resulted fromA3 sorghum × sudangrass crosses with this group ofinbreds. The line × cytoplasm interaction was significantfor percent seed set. Comparisons of line × cytoplasmcombinations showed significant differences due to cy-toplasm for A1Martin vs. A3Martin (73 vs. 14% seedset) and AlWheatland vs. A3Wheatland (81 vs. 39%Table 2. Treatment means for percent seed set of sorghum ×sign sudangrass hybrids in alternative cytoplasm.Line Cytoplasm Seed set~"%Martin A1 73A3 14Wheatland A1 81A3 39KS24 A1 87A3 75Redbine 58 A1 94A3 82LSD (P = 0.05) 19Seed set under a selfing bag.seed set). No differences due to cytoplasm were shownfor A1KS24 vs. A3KS24 (87 vs. 75% seed set) and Redbine 58 vs. A3Redbine 58 (94 vs. 82% seed set).The significant fertility restoration observed in A3hybrids was unexpected, since few sources of fertilityrestoration of A3 male-sterility have been known toexist (Bosques-Vega et al., 1989; Torres-Cardona, 1990).One possible explanation for the level of A3 fertilityrestoration in this experiment is that the sudangrasspopulations used as the bulk pollinator contain a rela-tively high level of A3 fertility restorers. A second possi-ble explanation involves two immediate sources of A3cytoplasm and their interaction with the female linesused in this study. A3KS24 (A3IA78), A3Wheatland(A3IA79), and A3Redbine 58 (A3IA80) were devel-oped using A3Tx3197 (ISl112C) cytoplasm, and exhibitsmall, shrunken, pale yellow or white anthers, as com-pared with the plump, dark yellow anther characteristicsof A3Tx398 (A3Martin) (R. E. Atkins, 1990). In experiment, fertility restoration in A3Tx398 was 14%.Fertility restoration in A3IA78, A3IA79, and A3IA80was 75, 39, and 82% respectively. In other experiments,hybrids made from the same pollen source on A3Tx7000and A3Tx430 and grown under the same conditions in1990 and 1991 exhibited fertility restoration of 9 and1%, and 5 and 1%, respectively.Plant Height and YieldDifferences among hybrids for height were expectedbecause of known height differences in the lines usedas seed parents, and were detected at the first harvest(Table 1). Height differences were not detectable regrowth at the second harvest. Cytoplasm had no inde-pendent or interaction effects on the height of hybridsat either harvest.Martin hybrids had higher total dry matter yield thanWheatland (Table 1). No differences in dry matter yielddue to seed parent line were detected at either the firstor second harvest, however. Cytoplasm had no indepen-dent or interaction effects on total yield, or yield ateither first or second harvest.Forage QualityThe range of mean values for these traits was smallamong hybrids with the four lines as seed parents. Nosignificant differences due to lines used as seed parentsNOTES 1975or cytoplasm, or their interactions, were detected forIVDMD or crude protein (Table 1). The potential im-pact of removal of seed as a photosynthetic sink (in A3cytoplasm hybrids) was negated by harvesting the forageprior to seed set in this experiment, but could also benegated by the unexpected high amount of fertility res-toration (seed set under selfing bags) observed in someof these hybrids.ConclusionWithin the limits of the environments, techniques, andgenetic resources used in this experiment, A3 cytoplasmappears to have no effect when compared with Al cyto-plasm for maturity, height, yield, or forage quality ofsorghum X sudangrass hybrids. For some hybrids, fertil-ity restoration using bulk pollen from several sudangrasspopulations was equivalent in Al and A3 cytoplasm.For other hybrids, fertility restoration was much lowerin A3 cytoplasm, but was still higher than would havebeen expected based on the literature. These A3 fertilityrestoration results suggest that the sudangrass popula-tions used in this study may contribute much neededA3 restorers to the sorghum industry. These results,however, clearly indicate the need to further explorefertility restoration interactions among A3 cytoplasmsources and various lines crossed into these cytoplasmsources.

Notes: Forage Yield, Quality,
And Fertility Of Sorghum X
Sudan Grass Hybrids In A1
And A3 Cytoplasm

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University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Agronomy & Horticulture -- Faculty Publications Agronomy and Horticulture Department 
1997 
Notes: Forage Yield, Quality, And Fertility Of Sorghum X Sudan 
Grass Hybrids In A1 And A3 Cytoplasm 
Jeffrey F. Pedersen 
University of Nebraska-Lincoln, jpedersen1@unl.edu 
J. J. Toy 
University of Nebraska-Lincoln, John.Toy@ars.usda.gov 
Follow this and additional works at: https://digitalcommons.unl.edu/agronomyfacpub 
 Part of the Agricultural Science Commons, Agriculture Commons, Agronomy and Crop Sciences 
Commons, Botany Commons, Horticulture Commons, Other Plant Sciences Commons, and the Plant 
Biology Commons 
Pedersen, Jeffrey F. and Toy, J. J., "Notes: Forage Yield, Quality, And Fertility Of Sorghum X Sudan Grass 
Hybrids In A1 And A3 Cytoplasm" (1997). Agronomy & Horticulture -- Faculty Publications. 957. 
https://digitalcommons.unl.edu/agronomyfacpub/957 
This Article is brought to you for free and open access by the Agronomy and Horticulture Department at 
DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Agronomy & Horticulture -- 
Faculty Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
NOTES
FORAGE YIELD, QUALITY,
AND FERTILITY OF SORGHUM x
SUDAN GRASS HYBRIDS IN A1
AND A3 CYTOPLASM
J. F. PEDERSEN* AND J. J. TOY
Abstract
Currently, no information is available comparing the agronomic
performance of A1 and A3 cytoplasms in sorghum x sudangrass
[Sorghum bicolor (L.) Moench] hybrids. The objectives of this study
were to compare the effects of A1 and A3 cytoplasm on the maturity,
fertility, height, forage yield, and forage quality of sorghum × su-
dangrass hybrids. In 1989, pollen from a bulk of eight sudangrass
populations was used to pollinate four sorghum lines that had been
male-sterilized in both A1 and A3 cytoplasm. Hybrids were grown
at the Univ. of Nebraska Field Laboratory, Ithaca, NE, in 1990 and
1991, in a split-plot design with inbreds (females) treated as whole
plots and cytoplasms treated as subplots. The soil was a Sharpsburg
silty clay loam (fine montmorillonitic, mesic Typic Agriudoll). Cyto-
plasm had no effect on days to 50% anthesis, height, forage yield, in
vitro dry matter disappearance (IVDMD), or crude protein. Seed set
under selfing bags (fertility restoration) in A3 hybrids was observed,
with interaction among A3 cytoplasm sources and lines.
SORGHUM X SUDANGRASS hybrids provide valuable for-
age for livestock consumption and ground cover
over a broad geographic region. Important attributes of
these hybrids include rapid growth, heat and drought
tolerance, and high yield. With the discovery of A1
cytoplasmic male-sterility (Stephens and Holland,
1954), a method became available to produce large
quantities of hybrid seed on grain sorghum females with
a minimal amount of effort. Commercial production
of sorghum × sudangrass hybrid seed is estimated at
45 400 000 kg annually (Kalton, 1989).
Several sorghum lines male-sterilized in an alternate
cytoplasm, A3, have been available since the early 1990s
(Atkins, 1990; Schertz et al., 1990). Grain sorghum hy-
brids produced by topcrossing 18 different lines onto
one of these A3 lines were all male-sterile (Lee et al.,
1992). Currently, no information is available comparing
the agronomic performance and quality of A1 and A3
sorghum × sudangrass hybrids. A3 sorghum × su-
dangrass hybrids should be expected to be male-sterile.
If grown in isolation, such male-sterile hybrids would
not set seed, possibly resulting in high forage quality
J.F. Pedersen and J.J. Toy, USDA, ARS, NPA Wheat Sorghum and
Forage Research, Dep. of Agronomy, Univ. of Nebraska-Lincoln,
Lincoln, NE 68583-0937. Joint contribution of the USDA-ARS and
the Nebraska Agric. Exp. Stn. Published as Paper no. 11756, Journal
Ser., Nebraska Agric. Exp. Stn. Received 16 Dec. 1996. *Correspond-
ing author (Email: agro137@unl.edu).
Published in Crop Sci. 37:1973-1975 (1997).
by eliminating seed production. Additionally, A3 male-
sterilization of sorghum lines used as pollinators (fertil-
ity restorers) in A1 hybrid production systems would
provide an entirely new heterotic gene pool for sor-
hum × sudangrass hybrid production. Recently, we re-
leased 18 combine height grain sorghum lines sterilized
in A3 (Pedersen et al., 1997) and 29 forage sorghum
cultivars male-sterilized in A3 cytoplasm (Pedersen and
Toy, 1997). These new genetic resources could provide
some practical benefits for grain sorghum seedsmen as
well as forage producers.
The objective of this study was to compare the effects
of A1 and A3 cytoplasms on the maturity, fertility, stat-
ure, forage yield, and forage quality of sorghum × su-
dangrass hybrids.
Materials and Methods
In 1989, pollen from a bulk of eight sudangrass populations
(NP22, NP23, NP25, NP28, NP29, NP30, NP31, and NP35)
was used to pollinate four combine-height sorghum lines that
had been male-sterilized in both A1 and A3 cytoplasm:
A1Martin and A3Tx398 (A3Martin), AiRedbine 58 and
A3IA78 (A3Redbine 58), AlWheatland and A3IA79
(A3Wheatland), and A1KS24 and A3IAS0 (A3KS24) (Atkins,
1990; Schertz, 1984).
Hybrids were planted on 21 May 1990 and 21 May 1991,
at the Univ. of Nebraska Field Laboratory, Ithaca, NE, in
a split-plot design replicated three times with seed parents
(females) treated as whole plots, and cytoplasms treated 
subplots. Individual plots were two rows 6.5 m long and 0.76
m apart. The entire experiment was planted twice to allow
collection of forage yield, quality, maturity, and seed set data.
Ammonium nitrate fertilizer was applied prior to planting
at 78 kg N ha-1. Propachlor {2-chloro-N (1-methylethyl)-
N-phenylaetamide/Atrazine [6-chloro-Nethyl-N-(1-methyl-
ethyl)-l,3,5,-triazine-2.4.-diamine]} was applied at 9.4 L ha-~
immediately after planting for weed control. Days to 50%
anthesis was recorded every 2 d during the blooming period.
Several panicles per row were bagged prior to anthesis and
visually evaluated for percent seed set at maturity. Forage
was harvested after all hybrids had reached the boot stage on
19 July 1990 and 26 Sept. 1990, and 16 July 199l and 19 Aug.
1991, with an automated plot harvester (Pedersen and Moore,
1995) to a stubble height of 10 cm, and weighed. Subsamples
were used to determine dry matter, and for subsequent qual-
ity analyses.
Subsamples were dried in a forced-air oven at 60°C and
ground in a Wiley mill (Arthur H. Thomas, Philadelphia, PA),
followed by grinding in a Udy cyclone mill (Udy Corp., Fort
Collins, CO) to pass a l-ram screen. Dry matter yield for each
cutting was calculated as fresh yield × percent dry matter,
and total dry matter yield for each year was calculated as the
sum of the two individual cuttings each year. In vitro dry
matter disappearance was determined as per Marten and
Barnes (1980) and crude protein was determined as per AACC
(1983). Data were analyzed with the appropriate test terms
for the split-plot design using the general linear models proce-
dure of SAS (SAS, 1989). Where significant differences were
Abbreviations: IVDMD, in vitro dry matter disappearance.
1973
Published November, 1997
1974 CROP SCIENCE, VOL. 37, NOVEMBER-DECEMBER 1997
Table 1. Treatment means for days to 50% anthesis, height, dry matter yield, in vitro dry matter disappearance (IVDMD), and crude
protein at first and second harvest dates (cuts) of sorghum × sign sudangrass hybrids.
Height Dry matter yield Crude proteinDays to 50%
Variable Level anthesis Cut 1 Cut 2 Cut 1 Cut 2 Total Cut 1 Cut 2 Cut 1 Cut 2
IVDMD
Line
Cytoplasm
% -- cm -- -- kg ha -l -- g kg-t
Martin 70 174 217 3742 6168 11 582 635 618 126 100
Wheatland 76 167 212 3002 5579 9 892 641 603 125 90
KS24 72 186 213 3577 5700 10 405 635 606 118 90
Redbine 58 69 186 217 3734 6187 11 293 632 592 120 97
LSD (P = 0.05) 3 18 nst ns ns 1 671 ns ns ns ns
A1 72 177 216 3516 5848 10 760 637 602 122 94
A3 72 179 213 3512 5969 10 826 635 607 123 95
Contrast (P = 0.05) ns ns ns ns ns ns ns ns ns ns
~ ns = not significantly different at P = 0.05.
indicated by the F-test, least significant differences (LSD)
were calculated. Single degree of freedom comparisons were
made for the two cytoplasms. Single degree of freedom com-
parisons were made within lines for cytoplasm effects where
significant line × cytoplasm interaction terms were present.
Results and Discussion
Although year effects were significant for several vari-
ables, no year interactions were significant. Therefore,
all results were pooled across years.
Maturity
Differences among hybrids for days to 50% anthesis
were expected due to known maturity differences in the
lines used as seed parents, and were detected (Table 1).
Cytoplasm had no effect on days to 50% anthesis, with
hybrids in A1 or A3 cytoplasm both averaging 72 d to
50% anthesis. Line × cytoplasm interactions were not
significant for days to 50% anthesis.
Fertility
Differences in percent seed set (under selfing bags)
among seed parent lines indicate that variability for
fertility restoration exists among these hybrids (Table
2). Percent seed set (or fertility restoration) by 
dangrass was greater on average in A1 cytoplasm than
in A3, but no fully male-sterile hybrids resulted from
A3 sorghum × sudangrass crosses with this group of
inbreds. The line × cytoplasm interaction was significant
for percent seed set. Comparisons of line × cytoplasm
combinations showed significant differences due to cy-
toplasm for A1Martin vs. A3Martin (73 vs. 14% seed
set) and AlWheatland vs. A3Wheatland (81 vs. 39%
Table 2. Treatment means for percent seed set of sorghum ×
sign sudangrass hybrids in alternative cytoplasm.
Line Cytoplasm Seed set~"
%
Martin A1 73
A3 14
Wheatland A1 81
A3 39
KS24 A1 87
A3 75
Redbine 58 A1 94
A3 82
LSD (P = 0.05) 19
Seed set under a selfing bag.
seed set). No differences due to cytoplasm were shown
for A1KS24 vs. A3KS24 (87 vs. 75% seed set) and 
Redbine 58 vs. A3Redbine 58 (94 vs. 82% seed set).
The significant fertility restoration observed in A3
hybrids was unexpected, since few sources of fertility
restoration of A3 male-sterility have been known to
exist (Bosques-Vega et al., 1989; Torres-Cardona, 1990).
One possible explanation for the level of A3 fertility
restoration in this experiment is that the sudangrass
populations used as the bulk pollinator contain a rela-
tively high level of A3 fertility restorers. A second possi-
ble explanation involves two immediate sources of A3
cytoplasm and their interaction with the female lines
used in this study. A3KS24 (A3IA78), A3Wheatland
(A3IA79), and A3Redbine 58 (A3IA80) were devel-
oped using A3Tx3197 (ISl112C) cytoplasm, and exhibit
small, shrunken, pale yellow or white anthers, as com-
pared with the plump, dark yellow anther characteristics
of A3Tx398 (A3Martin) (R. E. Atkins, 1990). In 
experiment, fertility restoration in A3Tx398 was 14%.
Fertility restoration in A3IA78, A3IA79, and A3IA80
was 75, 39, and 82% respectively. In other experiments,
hybrids made from the same pollen source on A3Tx7000
and A3Tx430 and grown under the same conditions in
1990 and 1991 exhibited fertility restoration of 9 and
1%, and 5 and 1%, respectively.
Plant Height and Yield
Differences among hybrids for height were expected
because of known height differences in the lines used
as seed parents, and were detected at the first harvest
(Table 1). Height differences were not detectable 
regrowth at the second harvest. Cytoplasm had no inde-
pendent or interaction effects on the height of hybrids
at either harvest.
Martin hybrids had higher total dry matter yield than
Wheatland (Table 1). No differences in dry matter yield
due to seed parent line were detected at either the first
or second harvest, however. Cytoplasm had no indepen-
dent or interaction effects on total yield, or yield at
either first or second harvest.
Forage Quality
The range of mean values for these traits was small
among hybrids with the four lines as seed parents. No
significant differences due to lines used as seed parents
NOTES 1975
or cytoplasm, or their interactions, were detected for
IVDMD or crude protein (Table 1). The potential im-
pact of removal of seed as a photosynthetic sink (in A3
cytoplasm hybrids) was negated by harvesting the forage
prior to seed set in this experiment, but could also be
negated by the unexpected high amount of fertility res-
toration (seed set under selfing bags) observed in some
of these hybrids.
Conclusion
Within the limits of the environments, techniques, and
genetic resources used in this experiment, A3 cytoplasm
appears to have no effect when compared with Al cyto-
plasm for maturity, height, yield, or forage quality of
sorghum X sudangrass hybrids. For some hybrids, fertil-
ity restoration using bulk pollen from several sudangrass
populations was equivalent in Al and A3 cytoplasm.
For other hybrids, fertility restoration was much lower
in A3 cytoplasm, but was still higher than would have
been expected based on the literature. These A3 fertility
restoration results suggest that the sudangrass popula-
tions used in this study may contribute much needed
A3 restorers to the sorghum industry. These results,
however, clearly indicate the need to further explore
fertility restoration interactions among A3 cytoplasm
sources and various lines crossed into these cytoplasm
sources.


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Notes: Forage Yield, Quality, And Fertility Of Sorghum X Sudan Grass Hybrids In A1 And A3 Cytoplasm

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