Submitted to: Wheat Genetics International Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 9, 2003
Publication Date: September 1, 2003
Citation: Anderson, J.M., Williams, C.E., Goodwin, S.B., Scofield, S.R., Ohm, H.W. 2003. Quantitative analysis of wheat defense-gene expression in response to insect, fungal, and viral pests. In: Proceedings of the Tenth International Wheat Genetics Symposium, September 1-6, 2003. Paestum, Italy. 1:323-326. Interpretive Summary: The United States produced 2.34 billion bushels of wheat in 2003 on 52.8 million acres. Diseases cause 2 to 10% yield loss annually resulting in economic losses of $1.5 to $10 billion dollars. The primary pathogens/pests of wheat that cause these yield losses are fungi, viruses and insects. Breeding for the genetic traits leading to resistance is a central part of reducing yield losses. However, to effectively use specific and non-specific resistance through a breeding program it is critical to understand how wheat responds to these pathogens/pests. Consequently, we have examined the expression patterns of genes previously shown to be turned on in plants to an array of pathogens and pests. Following inoculation or infestation with barley and cereal yellow dwarf viruses, Hessian fly, septoria tritici leaf blotch, and Fusarium head blight, this study showed that recognition of these pests by wheat occurs within hours or days after exposure to the pest leading to a rapid activation of stress and defense-related gene activity. However, there are significant differences between the response of wheat to these pathogens/pest. These results are beginning to illustrate the cellular processes leading disease resistance and will be used by scientists as a base of information to continue defining processes leading to resistance.
Technical Abstract: A significant component of resistance in wheat is the generalized host response to an array of pathogens and pests. Defense-response (DR) gene expression was quantified following infestation/inoculation with Hessian fly (Mayetiola destructor), fungi (Fusarium graminearum and Mycosphaerella graminicola) or barley and cereal yellow dwarf viruses. The expression of 20 DR genes was monitored in Hessian fly-resistant (H13) wheat tissue. Several genes were severely down-regulated two hours after attack by virulent larvae (receptor-like kinase, GST, catalase, aconitase, PAL, LOX, Hsp70, rubisco), but were unchanged with avirulent larvae. However, 24-48 hours after attack by avirulent larvae, several DR genes were up-regulated (LOX, Beta-1,3-glucanase, PR1). With Fusarium Head Blight, three cytochrome P450 genes, one chitinase gene and one unknown gene (putative retroelement) were up-regulated after inoculation of the resistant line Ning7840. Mycosphaerella graminicola resistant and susceptible lines displayed an early and strong response to the pathogen, with maximum expression of three genes encoding pathogenesis-related proteins, PR-1, PR-2 and PR-5, occurring within 12 hours of inoculation, followed by a sharp decline. Induction was highest in the resistant lines. PR-1.2, GST, PR-5 and WCI-1 showed increased expression in both BYDV/CYDV resistant and susceptible lines with some genes showing greater induction in the susceptible line.