Jank, Liana

Resende, Rosangela M. S.

Simioni, C.

Valle, Cacilda B.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings XXI International Grassland Congress / VIII International Rangeland Congress Polyploidization of Sexual Diploid Brachiaria decumbens for Intraspecific Hybridization Cacilda B. Valle EMBRAPA, Brazil C. Simioni CNPq/Fundect, Brazil Liana Jank EMBRAPA, Brazil Rosangela M. S. Resende EMBRAPA, Brazil Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/12-2/14 The XXI International Grassland Congress / VIII International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅱ 　 瞯 ]395　 瞯Grasslands/Rangelands Production Systems——— Developing Improved PlantsPolyploidization of sexual diploid Brachiaria decumbens for intraspecific hybridizationC .B . V alle1 倡 ,C . S imioni2 , L . Jank 1 倡 ,R . M . S . Resende11 Embrapa Bee f Cattle , Caixa Postal 154 , 79002‐970 Campo Grande , MS , Braz il , cacilda＠ cnp gc .embrapa .br , 倡 CNPqScholar ; 2 Pos‐Doc , CNPq Scholarship at Embrap a Bee f Cattle Caixa Postal154 , 79002‐970 Campo Grande ,MS , Braz ilKey words : apomixis ,chromosome duplication ,forage breeding ,polyploidization ,signalgrassIntroduction Brachiaria decumbens (D) , also known as signalgrass , is the most widely adapted forage grass in the tropics . Itwas first introduced to Brazil in the early １９５０′s and its best known cultivar , cv . Basilisk , quickly spread to the acid savannasof Latin America , covering millions of hectares . It is a natural tetraploid (４x ) and apomictic genotype of good dry matter andseed production , even though it is susceptible to spittlebugs , the most widespread insect pest in tropical pastures . Breeding ofthis species was restricted to using ４x apomictic accessions as pollen donors in interspecific crosses , since sexual genotypes arediploid (２x ) . Earlier attempts of interploydic crosses were unsuccessful ( Ferguson and Crowder , １９７４ ; Hacker , １９９４) . Thispaper is the first report of the use of in vitro culture and colchicine treatments in tetraploidizing sexual genotypes of signalgrass .Material and methods Plant meristems of several genotypes were isolated , inoculated in LS culture medium , and shoots obtainedwere transferred to MS medium for rooting . Basal segments were then separated and placed for ４８ hours , on LS mediumcontaining ０ .０１％ colchicine . Surviving plants were later transferred to the greenhouse then to the field for evaluation .Chromosome countings were done both on root tips ( mitosis) and in microspores ( meiosis) . Mode of reproduction was assessedusing the Young et al . , (１９７９) clearing technique and interference contrast microscopy .Results From １６２８ meristems extracted , ３７３ were treated with colchicine and ８７ plants were recovered . The main problem wasavoiding contamination in tissue culture since meristems were extracted from plants in pots . Until now , ２１ were examined forploidy level and cD２４‐２ , cD２４‐２７ and cD２４‐４５ were confirmed as tetraploid either in mitosis or both meiosis and mitosis .Despite treating several accessions , duplication was achieved only in accession D２４ , more responsive than others to tissueculture and colchicine treatment . Duplicated plants maintained sexual behavior as determined by microscopic analysis of embryosacs . Chromosome behavior on tetraploidized plants and pollen viability were assessed ( Tables １ and ２ ) . Most chromosomesassociated as bivalents but multivalents were also observed ( Table ２ ) . Several meiotic abnormalities were observed in varyingfrequencies , such as early migration to the poles , laggard chromosomes , and loss of DNA in micronuclei and microcytes .Table 1 Pollen v iability in induced tetrap loid p lants o fBrachiaria and on apomictic genotype used f or crosses .Plant ％ tetradsin meiosis Viable( ％ ) Unviable( ％ )TotalgrainsanalyzedcD２４‐２ (９１ q.５％ ６４ ?.８６ ３５ 貂.１４ ６２９ "cD２４‐２７ ?９７ q.６％ ６１ .３６ ３８ 貂.６４ １０３０ 9cD２４‐４５ ?９４ q.６％ ６３ .２５ ３６ 貂.７５ ９２８ "B .decumbenscv Basilisk ‐ ７３ ?.８２ ２６ 貂.１２ １１０４ 9Table 2 Chromosome association in meiosis o f inducedtetrap loid genoty pes o f Brachiaria .Plants Numberof cellsanalyzedAverage chromosome associationⅠ Ⅱ Ⅲ Ⅳ ,Ⅴ ,ⅥcD２４‐２ 妹５２ 趑０ 1.１１(０‐２) １６ 哪.９２(１２‐１８) ０ ).１１(０‐２) ０ 挝.４２(０‐３)cD２４‐２７ 谮３０ 趑０ 1.７７(０‐１０) １５ 哪.２６(８‐１８) ０ @.５(０‐３) ０ 挝.２６(０‐３)cD２４‐４５ 谮７０ 趑０ 1.１９(０‐２) １６ 圹.２(８‐１８) ０ ).１３(０‐２) ０ 挝.７６(０‐４)Conclusions Through many attempts , it was possible to obtain artificially tetraploidized sexual genotypes of signalgrass usingtissue culture and colchicine . There were clear differences between genotypes in response to polyploidization . These are thefirst sexual compatible signalgrass genotypes , a novelty that will allow intraspecific hibridization with natural superior apomicticaccessions in this important pasture species for the tropics .ReferencesHacker , J .B . １９８８ . Sexuality and hybridization in signalgrass , Brachiaria decumbens . T rop ical G rasslands , ２２ :１３９‐１４４ .Ferguson , J .E . ; L .V . Crowder . １９７４ . Cytology and breeding behavior of Brachiaria ruz iz iensis Germain et Evrard . CropScience , １４ : ８９３‐８９５ .

Polyploidization of Sexual Diploid \u3ci\u3eBrachiaria decumbens\u3c/i\u3e for Intraspecific Hybridization

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Polyploidization of Sexual Diploid \u3ci\u3eBrachiaria decumbens\u3c/i\u3e for Intraspecific Hybridization

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