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marker-assisted selection in wheat - ictsd

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Chapter 3 – Molecular <strong>marker</strong>s for use <strong>in</strong> plant molecular breed<strong>in</strong>g and germplasm evaluation 39Table 3Examples of SSR <strong>marker</strong>s available across different plant speciesCommon name Species Number ofSSRsReferenceRice Oryza sativa 2240 McCouch et al., 2002Maize Zea mays 1669 MapPairs (mp.<strong>in</strong>vitrogen.com)Soybean Glyc<strong>in</strong>e max 597 MapPairs (mp.<strong>in</strong>vitrogen.com)Cassava Manihot esculenta 318 MapPairs (mp.<strong>in</strong>vitrogen.com)Arabidopsis Arabidopsis thaliana 290 MapPairs (mp.<strong>in</strong>vitrogen.com)Cotton Gossypium spp. 217 MapPairs (mp.<strong>in</strong>vitrogen.com)Sugar cane Saccharum spp. 200 www.<strong>in</strong>tl-pag.org/pag/9/abstracts/W30_04.htmlWheat Triticum aestivum 193 MapPairs (mp.<strong>in</strong>vitrogen.com)Grape Vitis v<strong>in</strong>ifera 152 noGroundnut Arachis hypogaea 110 Ferguson et al., 2004Cucumber Cucumis sativus 110 Fazio, Staub and Chung, 2002Peach Prunus persica 109 Aranzana et al., 2004Kiwifruit Act<strong>in</strong>idia spp. 105 Testol<strong>in</strong> et al., 2001Barley Hordeum vulgare 44 MapPairs (mp.<strong>in</strong>vitrogen.com)Potato Solanum tuberosum 31 Ghisla<strong>in</strong> et al., 2004P<strong>in</strong>e trees P<strong>in</strong>us spp. 28 MapPairs (mp.<strong>in</strong>vitrogen.com)Banana Musa spp. 28 MapPairs (mp.<strong>in</strong>vitrogen.com)Sweet potato Ipomoea batatas 26 MapPairs (mp.<strong>in</strong>vitrogen.com)Sugar beet Beta vulgaris 25 www.<strong>in</strong>tl-pag.org/pag/10/abstracts/PAGX_W306.htmlEggplant Solanum melongena 23 www.<strong>in</strong>tl-pag.org/pag/11/abstracts/P3b_P181_XI.htmlFrom: Thomson, Sept<strong>in</strong><strong>in</strong>gsih and Sutrisno, 2003 (repr<strong>in</strong>ted with permission of author)number of ways. For example, theyprovide:• the ability to screen <strong>in</strong> the juvenile stagefor traits that are expressed late <strong>in</strong> the lifeof the organism (i.e. gra<strong>in</strong> or fruit quality,male sterility, photoperiod sensitivity);• the ability to screen for traits that areextremely difficult, expensive or timeconsum<strong>in</strong>g to score phenotypically (i.e.quantitatively <strong>in</strong>herited or environmentallysensitive traits such as rootmorphology, resistance to quarant<strong>in</strong>edpests or to specific races or biotypes ofdiseases or <strong>in</strong>sects, tolerance to certa<strong>in</strong>abiotic stresses such as drought, salt andm<strong>in</strong>eral deficiencies or toxicities);• the ability to dist<strong>in</strong>guish the homozygousfrom the heterozygous conditionof many loci <strong>in</strong> a s<strong>in</strong>gle generationwithout the need for progeny test<strong>in</strong>g (asmolecular <strong>marker</strong>s are co-dom<strong>in</strong>ant);• the ability to perform simultaneousMAS for several characters at one time(or to comb<strong>in</strong>e MAS with phenotypic orbiochemical evaluation).This section provides examples ofhow molecular <strong>marker</strong>s are be<strong>in</strong>g used <strong>in</strong>breed<strong>in</strong>g and germplasm evaluation. Whilethese examples are drawn mostly from rice,they illustrate applications of MAS techniquesthat are used <strong>in</strong> other species.Before molecular <strong>marker</strong>s can be usedfor <strong>selection</strong> purposes, their associationwith genes or traits of <strong>in</strong>terest must befirmly established. While the number ofeconomically important genetic loci thathave been cloned or tagged via l<strong>in</strong>kage tomolecular <strong>marker</strong>s is still limited <strong>in</strong> mostspecies, work towards this end is accelerat<strong>in</strong>grapidly. This is particularly true <strong>in</strong>rice, due to the availability of completegenome sequence <strong>in</strong>formation.Nonetheless, a great deal of time andeffort is required to identify the geneticloci and specific allelic variants that areresponsible for the tremendous array of

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