What are the races of the “remnant” population of the pathogen?

Our field tests indicate the presence of new races of the pathogen in WSU, WA and UC Davis, CA

How diverse are the pathogen isolates?We are currently examining the extent of genetic

diversity of the field isolates of the pathogen by the use of amplified fragment length polymorphism (AFLP)

We are also studying the differences among the isolates from different locations by the use of molecular markers

Emerging and re-emerging plant diseases

In the past two decades, emerging and re-emerging plant diseases have posed new threats to food production. Emerging diseases are those which have always been present in an area but have grown in importance over the years. Re-emerging diseases are those that have been previously controlled but are once more a major problem. Diseases emerge or re-emerge due to changes in farming practices, development of new strains of the pathogen, climate change, introduction of the pathogen to new geographical locations, or introduction of more efficient pathogen vectors.

Tilletia caries, causal agent of common bunt of wheat

Bunted and healthy kernels

Fig. 2. Percent bunt infection of selected winter wheat cultivars.

Selected races of the bunt pathogen

Perc

ent

bunt

infe

ctio

n

Disease Status Crop host

Scab (Fusarium Head Blight) Re-emerging Wheat and barley

Karnal bunt & common bunt Emerging Wheat and other cereals

Tomato spotted wilt (tospovirus) & Tomato yellow leaf curl (geminivirus)

Re-emerging / Emerging

Tomato

Silver scurf, pink rot & dry rot Re-emerging Potato

Raspberry bushy dwarf (idaeovirus)

Re-emerging Raspberries

Anthracnose Emerging Strawberry

Blueberry shock (ilarvirus) New Blueberry

Black leg Re-emerging Cabbage, cauliflower, broccoli

High plains virus disease New Corn and other cereals

Sorghum ergot Emerging Sorghum

Potato late blight (new strains) Re-emerging Potato & tomato

What are the bunt resistance genes in modern wheat cultivars?

Table 1. New, emerging and re-emerging diseases of selected crops in the United States.

Janet B. Matanguihan and Stephen S. JonesDepartment of Crop and Soil Sciences, Washington State University

Mount Vernon Northwestern Washington Research and Extension Center

We will identify the bunt resistance genes present in 12 selected modern wheat cultivars

We will use molecular markers and nulli-tetrasomic lines of wheat to identify the location of the resistance genes in specific wheat chromosomes

Fig. 1. Major pathogens causing emerging infectious plant diseases (Anderson et.al. 2004)

Impact of emerging plant diseases:

Threat to human welfare~ 42% of the attainable crop production is lostBarrier to international commerceNegative effects on health and well-being

Threat to biodiversity and ecosystemsDecline of host populationsExtinction of host species or other organisms dependent on

the host for habitat

What should be done?

Damsteegt, 1999; Fry and Goodwin, 1997; du Toit, L. (pers.comm); Inglis, D. (pers.comm); Manners, 2004; McMullen et.al. 1997; Randyopadhyay & Frederiksen, 2004; www.ces.ncsu.edu/depts/ent/clinic

HOST RESISTANCEPre-emptive breedingDurable/broad resistance

MANAGEMENT PRACTICESExamine impactHost diversity

MONITORING (local & global)Identification/diagnosticsPathogen virulence & genetics

QUARANTINE (local, national & global)

Scientific principles of plant protection

Risk assessmentPolicy adoptionEducation

Adapted from Fry and Goodwin, 1997; Manners, 2004

Fusarium head blight (Photo by M. McMullen)

Karnal bunt on grains, www.apsnet.org

Late blight of potato, www.ctahr.hawaii.edu

Tomato spotted wilt, www.colostate.edu

http://ipm.ncsu.edu

Blueberry shock, http://whatcom.wsu.edu

Ergot of sorghum (photos by G. Obvody)