Development of male sterile forage sorghum genetic stock in A3 cytoplasm

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تطوير أول أمهات سودانية عقيمة الذكر من الذرة الرفيعة توضح هذه الدراسة تطوير أول أمهات سودانية من الذرة الرفيعة تحمل العقم الذكري السيتوبلازمي من النوع الثالث. و تنبع أهمية هذا العمل فى انه يفتح الطريق للمرة الأولى لتطوير أول هجين علف ذرة رفيعة سودانى 100% علما بأن الهجن المزروعة حاليا بالسودان كلها مستوردة و غير متأقلمة بما فيه الكفاية على البيئة السودانية. تم تطوير 12 أم عقيمة الذكر من سلالات منتخبة من عشيرة علف الذرة أبو سبعين فى الفترة 2001-2004 . و سيتم استعمال عدد من هذه السلالات فى تطوير أول هجين محلى لعلف الذرة رخيص التكلفة و أكثر تأقلماً مقارنة مع الهجن المستوردة This study demonstrates for the first time developing of Sudanese sorghum male sterile lines in A3 cytoplasm. Twelve Abu Sab’in females, closely resembling their fertile counterparts and completely male sterile were developed. They are expected to transmit their growth vigor, adaptability, earliness and other desirable traits to their progenies. Such traits, which are largely lacking in exotic x exotic hybrids, are highly recommended under the local production system and hoped to enhance production of cheep and better adapted forage sorghum hybrids.
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    In the Sudan, no locallydeveloped forage hybrid has beenreleased up to date. However, the firstSudan-grain hybrid sorghum wasreleased in 1983 (Ejeta, 1983).According to ElAhmadi et al. (2003),until the early eighties, the open pollinated cultivar ‘Abu Sab’in’ was theonly sorghum type grown for forage inthe country. Pioneer 988, the firstintroduced forage sorghum hybrid in theSudan, was released in 1989 (Ishag,1989). A number of introduced hybridswere also released during the 1990s.Although exotic x exotic hybrids provedto be good yielders, the farmer’s preference was, however, in favor of thetraditional cultivar Abu Sab’in. Most of the introduced hybrids were designed tosuit the grazing or silage-making systems prevailing in countries other than Sudan.The low adoption of the exotic hybridsmay also be attributed to unavailabilityand high cost seeds. Work on the possibility of breeding for local x exoticforage sorghum hybrids in the Sudanusing exotic females in A3 cytoplasmresulted in hybrids that excelled the parental lines and the commercial hybrid.However, the exotic females were foundresponsible for transmitting undesirabletraits (Mohammed, M.I. unpublishedreport). The choice for developing local xlocal hybrids was therefore, thoughtcrucial in resolving problems pertainingto the poor adoption of forage sorghumhybrid in Sudan. This in turn necessitatesthe need for male-sterilizing the localstocks. The A3 CMS sterility sourceseems to be the most appropriate as itmaintains male sterility in most genetic- backgrounds. Moreover, it allows production of male sterile hybrids(Pedersen and Toy 1997), a situation thatoffers a theoretical possibility for qualityimprovement by eliminating seed as astrong carbohydrate sink. A verycommon practice adopted by Abu Sab’ingrowers is to delay cutting until grainformation. As stated by Bacon (1948) thegrains being produced were invariablyeaten by sparrows and the farmer usuallyend up with a straw of a lowered feedingvalue. Thus, sterile hybrids suit nicelythe locally adopted green choppingsystem in which seed formation is notimportant as in silage-making system.The objective of this investigation was todevelop local forage sorghums females by male-sterilizing the local stocks in A3cytoplasm.Twenty nine forage sorghumgenetic stocks in A3 cytoplasm werereceived from J.F. Pedersen, USDA-ARS; University of Nebraska. Of these,eight genetic stocks were used in thecrossing program, namely, A3N161,A3N171, A3N155, A3N149, A3N153,A3N163, A3N173 and A3N151. Alleight lines have A3 cytoplasmsrcinating from IS1112C (SC193)obtained from A3T x 398 (Pedersen andToy, 1997).Thirteen genotypes from thematerial developed by the ForageImprovement Program at ShambatResearch Station were identified andused as recurrent parents. Tewelve of these genotypes were Abu Sab'inselections. The other genotype (B-4) wasreceived from A.B. ElAhmadi, Head of the Research Unit - Sudanese ArabCompany for Seed Production,Khartoum. The Abu Sab'in lines wereindividual plant selections chosen from asource population comprising the twomajor types of the local forage cultivar  NotesA note on development of male strile forage sorghum genetic stock in A3 cytoplasm Maarouf I. Mohammed 1   1 Forage breeder, Shambat ResearchStation.P.O. box 30, Khartoum North, Sudan E-mail:ibrahimarof@yahoo.com    Sudan . aric. res. 2004 4 89-92 A R T C Sudan E.mail: arcdsudanmail.net    Abu Sab’in, known as, Aliab andRubatab. The recurrent parents werevariable in days to flower, plant heightand mid-rib color.The backcross breeding procedure was followed to transfer thechromosomes of the local stocks in theA3 cytoplasm. The recurrent parentswere crossed to the A3 followed by four  backcross generations using twogenerations per year. In all generations,each A3 line was grown along with itsrespective recurrent parent. Thirty toforty heads in each A3 line were coveredwith pollinating bags prior to anthesis. Atthe appropriate time, about half of thecovered heads were hand pollinated andimmediately covered again. The heads of the other half were left without pollination to check for sterilityreactions. A new selection with a greenmid-rib was included during BC 1 byselection from S. 77 (White mid-rib).The progenies of the F 1 Waconia-L xS.72 and BC 1 (N 109 x B-4) x B-4showed partial fertility and werediscarded. The remaining progenies(totaling 12) that maintained malesterility up to the BC 4 were growntogether with their fertile counterparts(maintainers) for comparison andchecking for sterility reactions.Table 1 shows the twelve A3 CMS localgenetic stocks in BC 4 , their fertilecounterparts, cytoplasm source, backcross generations, and some of their  phenotypic characteristics. These geneticstocks (Abu Sab’in females) closelyresemble their fertile counterparts andwere completely male sterile at ShambatExperimental Farm as determined byisolation in the field under pollinating bags through all backcross generations.Sterility reactions under other environments have not been investigated.The newly developed A3 genetic stockshave immediate application as femalelines for producing F 1 hybrids under identical environments with reasonablegenetic variability for plant height daysto flower and mid-rib color. They areexpected to transmit their vigorousgrowth, adaptability, earliness and other desirable traits to their progenies. Suchtraits, which are largely lacking in exoticx exotic hybrids, are highlyrecommended under the local productionsystem. It may also be expected that, thenutritive value of their sterile hybrids bereserved within the vegetative portiondue to elimination of seed as a strongcarbohydrate sink. The use of the newlydeveloped females, if succeeded in producing local x local hybrids, arehoped to enhance production of cheepand better adapted forage hybrids. A breeding program along these lines will be initiated Acknowledgements Special thanks are due to J.F.Pedersen, Research Geneticist-Universityof Nebraska for providing and deliveringthe seed of the 29 forage sorghumgenetic stocks in A3 cytoplasm. Thanksare also due to the USDA-ARS, and theAgricultural Research Division, Instituteof Agriculture and Natural Resources,University of Nebraska, where thematerials were jointly developed. References Bacon, G. H. (1948). Crops of theSudan. In J.D. Tothill Ed.,“  Agriculture in the Sudan ”.Oxford University Press. London.Pp. 304-316Ejeta, G. (1983). Current status of sorghum improvement researchand development in the Sudan.In : G. Ejeta Ed., “  Hybrid Sorghum Seed in the Sudan ”.Proceedings. Purdue University.Pp. 11 - 18. Maarouf I. Mohammed 90    ElAhmadi, A.B.; Khair, M.A.Mand Maarouf I. Mohammed(2003). Comparative performanceof “Safed Moti”, a grain sorghumx Sudan grass hybrid from India.A paper submitted to the VarietyRelease Committee. ARC. W.Medani. Sudan.Ishag, H. M. (1989). Pioneer 988-a forage sorghum for irrigatedGezira. A report submitted to theVariety Release Committee.ARC. W. Medani. Sudan.Pedersen, J.F., and Toy, J.J. (1997).Registration of 29 foragesorghum genetic stocks in A3cytoplasm. Crop Sci. 37: 1408-1409. A note on development of male strile forage sorghum..   91    # : All in BC 4  (A), (R) = Abu Sab’in Aliab, and Abu Sab’in Rubatab, respectively.   Genetic Stock designation #CytoplasmsourceRecurrentParentDays to anthesis Plant height (cm) Mid-rib color Pericarp colorA3 geneticstock RecurrentparentA3 geneticstock RecurrentparentA3 geneticstock RecurrentparentA3geneticstock Recurrentparent A3SH1   A3Tx 398   S.3 (A) 57 58 261 266 G   G   White   White   A3SH2   A3Tx 398   S.66 (R)51 49 170 165 G   G   White   White   A3SH3 A3Tx 398   S.77-1 (A)60 59 270 275 W W White   White   A3SH4 A3Tx 398   S.77-2 (A)62 62 260 265 G   G   White   White   A3SH5   A3Tx 398   S.57 (R)55 55 130 130 W W White   White   A3SH6   A3Tx 398   S.79 (R) 51 51 158 160 G   G   White   White   A3SH7   A3Tx 398   S.93 (R)53 54 160 162 G   G   White   White   A3SH8   A3Tx 398   S.158 (R)54 52 180 170 G   G   White   White   A3SH9   A3Tx 398   S.148 (A)58 57 268 260 G   G   White   White   A3SH10   A3Tx 398   S.154 (A)60 59 268 267 G   G   White   White   A3SH11   A3Tx 398   S.138 (A) 64 65 290 290 W W White   White   A3SH12   A3Tx 398   S.134 (A) 61 60  257 259  G   G   White   White   Table 1. The 12 local forage sorghum genetic stocks (Abu Sab'in females) sterilized in A3 cytoplasm (Shambat  , 2004) G, W = green mid-rip (juicy) and white mid-rip color (non- juicy) respectively. Maarouf I. Mohammed 92
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