Lecture 8 – Rusts (Urediniales in Text, Pucciniomycotina in Tree of Life
http://tolweb.org/Pucciniomycotina/20528) – Teliomycetes II
Reading: Text, Chapter 5, http://tolweb.org/Pucciniomycotina/20528
http://www.cals.ncsu.edu/course/pp315/gene/
Objectives: Understand the function in pathogenesis and evolution of the
pathogen of each of the five spore-producing stages in a full-cycle rust.
Study Questions:
1. What are the 5 spore phases of the life cycle of Puccinia graminis?
Which are monokaryotic, which are dikaryotic? Which phase overwinters?
2. Which is more likely to be macrocyclic – an autoecious rust or a
heteroecious rust? Which is more likely to be demicyclic or microcyclic?
3. A forma specialis is a grouping within a species that is a specialized
pathogen of a specific host species (e.g. Triticum aestivum, wheat). A
physiological race is a grouping within a forma specialis that can only
infect certain host genotype(s). What is the gene-for-gene theory and
understand that it applies to the rank of race. How is this concept applied
to the breeding of resistant plants?
4. Some rusts are macrocyclic (like wheat stem rust), others are
demicyclic and lack a uredinial stage, others are microcyclic and have
teliospores as the only dikaryotic spore. Sketch out life cycles for wheat
stem rust, a microcyclic rust, and a demicyclic rust, figuring out how they
are going to infect the plant, reproduce and overwinter in a cold climate.
Keywords: Teliospore, promycelium,, haustoria, spermagonia, spermatia,
aeciospores, aecia, primary host, urediniospores, uredinia, telia, sori
(sorus is singular), heteroecious, autoecious, forma specialis, gene-forgene theory, host specificity, host range, race, cultivar, macrocyclic.