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Will my cultivar set seeds? Who will be the father?Controlling fertilization: Controlling fertilization Incompatibility Male sterility Genetic (nuclear) male sterility (MS) Cytoplasmic male sterility (CMS) Apomixis Interspecific hybridization Time of pollen shedSelf-Incompatibility (SI): Self-Incompatibility (SI) Compatible pollination pollen grains adhere to stigma, hydrate and germinate pollen tube penetrates stigma and grows down the style, fertilization of the ovule Self-incompatibility Related pollen does not fertilize eggcell: lack of germination, reduced pollen tube growth, blocked fertilisationSelf-incompatibility systems: Self-incompatibility systems Gametophytic SI the pollen phenotype is determined by its own haploid genotype Solanaceae, Papaveraceae, Rosaceae, Poaceae, Triticae Sporophytic SI the pollen phenotype is determined by the genotype of the pollen parent Brassicaceae, Asteraceae Gametophytic SI in the Solanaceae : Gametophytic SI in the Solanaceae Tobacco (Nicotiana), Petunia, tomato (Lycopersicon) Inheritance as a single locus (S) with multiple alleles (S1, S2, S3,…) Molecular studies: At least two tigthly linked loci Stylar S gene product has ribonuclease activity (S-RNase) Pollen S gene product is unknown Degradation of RNA in pollenGametophytic SI in the grass family (Poaceae): Gametophytic SI in the grass family (Poaceae) Inherited as two unlinked loci (S and Z) Both are multi-allelic (S1, S2, S3,… and Z1, Z2, Z3 …) Both S and Z in the pollen must match S and Z in the pistil to get incompatibility Hypothesis: at least two tigthly linked genes in each locus Gene products and mechanism unknownSporophytic SI in the Brassicaceae: Sporophytic SI in the Brassicaceae Inherited as a single locus (S) with multiple alleles (S1, S2, S3…) S locus consisting of 3 genes S locus glycoprotein (SLG) in stigma S locus receptor kinase (SRK) in stigma S locus cysteine-rich gene (SCR) in anthers Block in pollen hydration and germinationPollen tube growth in Brassica: Pollen tube growth in Brassica a) S8S8 stigma, S52S60 pollen b) S9S9 stigma, S52S60 pollen c) S8S8 stigma, S8 pollen d) S9S9 stigma, S52S60/transgene S8 pollen e) S8S8 stigma, S9 pollen f) S9S9 stigma, S9 pollen Shiba et al. (2001) Plant Physiol. 125:2095Self-incompatibility in Plant Breeding: Self-incompatibility in Plant Breeding Avoid inbreeding depression in varieties of cross-pollinating species Avoid self-fertilization in hybrid seed production When no efficient CMS system is available Pseudo self-fertility Seed set not comletely blocked Self-fertility alleles Weak SI alleles Male sterility, nuclear genes: Male sterility, nuclear genes MsMs and Msms plants are male fertile msms plants are male sterile A pure msms population can not be produced Why? Because msms plants can not be self-pollinated Pollinate with Msms plants and remove male fertile plants from the offspringCytoplasmic male sterility (CMS): Cytoplasmic male sterility (CMS) Controlled by mitochondrial genes Maternally inherited Used for hybrid production in many crops Onion, carrot, cabbage Corn, sorghum, pearl millet, sunflower, sugar beets Mutations or foreign cytoplasms Ogura cytoplasm in Brassica from radish CMS in onion: CMS in onion Allium galanthum CMS male sterile umbelRestorer genes: Restorer genes Nuclear genes (Rf) can restore male fertility (One locus restorer system) CMS, rfrf is male sterile CMS, Rfrf is male fertile CMS, RfRf is male fertile N, rfrf is male fertile N, Rfrf is male fertile N, RfRf is male fertileFlower phenotypes in carrot: Flower phenotypes in carrot a) Normal (N-cytoplasm, restored CMS plants) b) Brown anther CMS (Sa) c) Petaloid CMS (Sp)Fertility restoration in maize: Fertility restoration in maize From Roger Wise’ research lab. http://www1.iastate.edu/~imagefpc/Subpages/research.htmlSimple hybrid with cms and restoration: Simple hybrid with cms and restoration Maintainer line (B-line) N, rfrf Large amounts of CMS line x CMS line (A-line) CMS, rfrf Male line (C-line) N and RfRf Fertile F1 hybrid CMS, RfrfBreeding hybrid carrots: Breeding hybrid carrots Controlling fertilization: Controlling fertilization Self-incompatibility (SI) Homomorphic incompatibility Gametophytic Sporophytic Heteromorphic incompatibility (Primula) Male sterility Genetic (nuclear) male sterility (MS) Cytoplasmic male sterility (CMS) Gm male-sterility Gametocides Chemicals to kill pollenApomixis: Apomixis Seeds without fertilisation Pollination may or may not be needed to from viable seed (fertilisation of central nucleous) Obligate and facultitative apomicts Detrmined by genes in the plants Several mechanisms of function Clone cultivars by seeds but It is hard to make new crosses Kentucky bluegrass, Citrus You do not have the permission to view this presentation. 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