Incompatibility and cytoplasmic male sterility: Incompatibility and cytoplasmic male sterility Chapter 7. 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 shed
Self-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 fertilisation
Self-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 pollen
Gametophytic 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 unknown
Sporophytic 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 germination
Pollen 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. 125:2095
Self-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 offspring
Cytoplasmic 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 umbel
Restorer 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 fertile
Flower 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.html
Simple 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, Rfrf
Breeding 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 pollen
Apomixis: 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