ROBERT A. MCINTOSHTHE UNIVERSITY OF SYDNEY PLANT BREEDING INSTITUTE

COBBITTY, NSWAUSTRALIA

Historical Overview of Stripe Rust Research

TAXONOMY OF THE PATHOGEN

Reviewed and revised by Liu & Hambleton (2010)

- Uredo glumarum Schmidt - before 1819

- P. glumarum Eriks. & Henn. 1894 (until the 1950s)

- Puccinia striaeformis Westend. 1954

- P. striiformis

SPECIES SPECIALIZATION

Liu & Hambleton (2010) using its & beta-tubulins

-P. striiformis on the triticeae

-P. gansensus on achnatherum inebrians

P. striformoides on Dactylis glomerata

P. pseudostriiformis on Poa. spp.

f. sp. tritici

f. sp. hordei

f. sp. pseudohordei - PNW21?

Puccinia striiformisformae speciales

Almost worldwideHistorically considered to favour cooler areasRecent outbreaks defy assumptionsAre there unique aspects of environment that determine distribution?Are current races more adapted to high temperaturesWhat factors determine distribution within regions?

Puccinia striiformis tritici

Distribution

Up to 50%, but occasionally higher

Stripe rust losses

DISEASE CYCLEEpidemic Phase – during the cropping

cycleSurvival Phase – during the non-cropping

season

The rust pathogens are obligate parasites and need living plants to survive in the uredinial stages

During non-optimal periods one generation of the fungus may take longer than 1-2 weeks

LIFE CYCLE OF A RUST PATHOGEN

EPIDEMIOLOGY

- Role of the sexual hosts- What species of barberry?- Where?- Are they important in relation to Pst on wheat?

- Role of asexual hosts- What grass species?- Where?- Are they important in rust survival?

VOLUNTEER WHEAT IS PROBABLY THE MAIN SOURCE OF INOCULUM

PATHOGENIC VARIATION IN PST

Differential sets for seedling assaysWhy Have differential sets?Genetics of the differentialsRepeatability of dataNaming races

German, European, North American, Indian, Chinese

Environmental conditions for testing Differentials for field assays???

GENETICS OF RESISTANCE

Seedling resistances We still do not know the genetic bases of

resistance in differentials Problems in international race variation

Adult plant resistancesRecognized from the 1960s - Zadoks, Stubbs, Sharp, Bingham, Law

DURABILITY OF RESISTANCE

Resistances/resistance genes effective at the seedling stage have not proven to be durable. There are many genes of this type

At least some resistances/resistance sources for APR have proven durable. There are many genes of this type

BUT not all gene/gene sources for APR are durable

BREEDING FOR STRIPE RUST RESISTANCE

There is no shortage of resistanceResistance must be in the best varietiesWe must have rust to select for

resistance (even when we have markers!!)

Value of international testingProblems of lack genetic diversity

Megavarieties Copycat breeding

POST-RELEASE VARIETY MANAGEMENT

Avoid/Remove/Prevent/Discourage highly susceptible varieties – the bushfire effect!!Need to monitor pathogen populations over space and time – using differentials or markers

Need to monitor relative disease responses in relation to variety make-up, changing agronomic practices, climate change,

neighbours. Rust is a social issue At the international level need to build up

a co-operative attitude to information sharing, mutual sharing of risk analysis, and trust

WHAT MAKES RUST EXCITING