fourthlecture

Definitions: 

Definitions Alternatively fixed alleles Dominant vs. co-dominant markers Genotype

Alternatively fixed alleles:: 

Alternatively fixed alleles: Two flower species (species 1 and species 2) can have one of two features: Long (L) or short (s) leaves Red ( R) or white (w) flowers Ten individuals from species 1 have the following traits: LR; LR ;LR ;LR; LR; LR ;LR; sR; sR; sR Ten individuals from species 2 have the following traits: sw; sw ;sw ;sw; sw; sw ;sw; Lw; Lw; Lw

Which one is the alternatively fixed allele?: 

Which one is the alternatively fixed allele? Both alleles will differentiate the groups (frequencies are significantly different) Only one will be diagnostic because alternatively fixed It is the color of the flower: all flowers in species 1 are R, all flowers in species 2 are w (“all” implies your sampling size is adequate!!)

Dominant vs. co-dominant markers: 

Dominant vs. co-dominant markers Flowers are red or white or yellow, DNA sequence is agg, agt, agc; DNA fragment is 10, 12 0r 14 bp long (CO-DOMINANT, we know what alternative alleles are) Flowers are red or non-red, DNA is agg or not, size is 10bp or not. We only see the dominant allele and we express it in binary code 1(present), 0(absent)

Limitations of co-dominant markers: 

Limitations of co-dominant markers Not all non-red flowers are the same, but we assume they are (non red flowers can be orange or yellow) If at one locus we have a dominant A allele and a recessive a allele, using a codominant marker we would say AA=Aa but not aa. We know in reality AA and Aa are quite different.

Genotype: 

Genotype A unique individual as defined by an array of genetic markers. (the more markers you have the less mistaken identity you will have. blonde

Slide7: 

Blonde Blue-eyed

Slide8: 

Blonde Blue-eyed Hairy

Slide9: 

Blonde Blue-eyed Hairy 6 feet tall

Slide10: 

Blonde Blue-eyed Hairy 6 feet tall Missing two molars

In the case of microbes it will probably be something like: 

In the case of microbes it will probably be something like Genotype A= 01010101 Genotype B= 00110101 Genotype C= 00010101

Summary of third lesson: 

Summary of third lesson DNA polymorphisms can be diagnostic Mutations/Sex/Barriers to mating Plant Diseases can be biotic (interaction between host and causal agent ), or abiotic Many organisms can cause plant diseases, but fungi are the No.1 cause Diversity of fungi, but all have ideal structure for plant infection: hypha/cord/rhizomorph/infection peg/appressorium Sexual vs. asexual reproduction: can do both

Fungi… again!: 

Fungi… again! ASCOMYCETES BASIDIOMYCETES OOMYCETES (fungus-like, water molds)

ASCOMYCETES: 

ASCOMYCETES Yeasts (fermentation, human mycoses) Truffles, morels Penicillia (penicillin), Fusaria (potent toxins, damping off of seedlings), molds

Ascus is the sack in which the spores are contained: 

Ascus is the sack in which the spores are contained

Asci can be placed on a disk (apothecium), many apothecia can be together in a fruitbody: 

Asci can be placed on a disk (apothecium), many apothecia can be together in a fruitbody Morel fruitbody

Asci can be carried inside a flask (perithecium): 

Asci can be carried inside a flask (perithecium) Nectria

Slide21: 

Ploidy is mostly n

BASIDIOMYCETES: 

BASIDIOMYCETES Mushrooms. mycorrhizal Wood decay organisms Rusts, Smuts Yeasts and damping off

Toadstools and huitacochle are both basidiomycetes: 

Toadstools and huitacochle are both basidiomycetes

Basidium means “club”, it carries the basidiospores (dispersion propagules) naked: 

Basidium means “club”, it carries the basidiospores (dispersion propagules) naked

Slide27: 

Most of their life, they are n+n (dikaryons), some rare ones are diploid

Oomycetes: 

Oomycetes Belong to the kingdom Stramenopila, used to be called Chromista Phytophthora, Pythium, Saprolegnia H20

Slide29: 

Hyphae, sporangia, and zoospores of P. ramorum

Slide30: 

Most of their lifecycle they are 2n Have cellulose in cell wall Not fungi!!, but look like them because of convergent evolution

Fungi do not photosynthesize: 

Fungi do not photosynthesize Biotrophic: mycorrhyzae, rusts Endophites: clavicipetaceae, Necrotrophic; most pathogens Saprobes: primary (involved in litter decomposition)

DISEASE!!: 

DISEASE!! Symptoms vs. signs; e.g. chlorosis vs. fruit-body The disease triangle

host-pathogen-environment: 

host-pathogen-environment Susceptibility of individuals or of portions of individuals Genetic variability Basic compatibility (susceptibility) between host and pathogen Ability to withstand physiological alterations

Slide34: 

Genetic resistance in host

Slide35: 

Cankers by P. ramorum at 3 months from time of inoculation on two coast live oaks

host-pathogen-environment: 

host-pathogen-environment Basic compatibility with host (virulence) Ability to maintain diversity: sex vs. no sex Size of genetic pool Agressiveness (pathogenicity) towards hosts Ability to survive without host

Slide37: 

Chlamydospores of P. ramorum

host-pathogen-environment: 

host-pathogen-environment Temperatures Shading Relative humidity Free standing water pH and any potentially predisposing factors Nutrient status

Slide40: 

Colony diameter (mm) at 13 days

Presence of free water: 

Presence of free water Between 6 and 12 hours required for infection of bay leaves

Some pathogen roles in natural plant communities: 

Some pathogen roles in natural plant communities Selection of individuals best suited for the site Maintenance of genetic diversity and stability in host plant populations Establishment or maintenance of host geographic ranges Natural succession Regulation of stand density, structure, and composition

Human activities affecting disease incidence in forests: 

Human activities affecting disease incidence in forests Introduction of exotic pathogens Planting trees in inappropriate sites Changing stand density, age structure, composition, fire frequency Wound creation Pollution, etc.

Effects of fire exclusion: 

Effects of fire exclusion