ARS | Publication request: Comparative Analysis of Early Defense in Compatible and Incompatible Wheat-Powdery Mildew Interactions

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 6, 2004
Publication Date: April 1, 2005
Citation: Li, A., Wang, M.L., Zhou, R., Kong, X., Huo, N., Wang, W., Jia, J. 2005. Comparative analysis of early defense in compatible and incompatible wheat-powdery mildew interactions. Plant Pathology. 54:308-316

Interpretive Summary: Wheat powdery mildew is one of the important diseases which cause significant yield loss in wheat production. Most published papers reported plants late response to the fungi attack. This paper reports the early response to fungi attack. Different genetic lines derived from hybridize crossing were used and early responses have been observed. The purpose of this study is to associate different defense responses (phenotype) to genetic controls (genotype). This association will help us to understand the plant defense mechanism.

Technical Abstract: Comparative analysis was carried out for hydrogen peroxide (H202) accumulation in response to powdery mildew (Bulmeria graminis f.sp. tritici BgtE09) primary germ tube (PGT) and appressorial germ tube (AGT) formation, and in papilla (cell wall appositions) and hypersensitive responses (HR) in wheat (Triticum aestivum L.) This study was focused on the early defense responses between 10 to 48 hours after inoculation using primary leaves of three compatible (susceptible) (Bainong3217, Beijing 837 and Jingshaung16) and five incompatible (resistant) (Mardler [Pm2+Pm6], Ulka/8*Cc [Pm2], Mardler/7* Bainong3217F5) wheat lines. More significant numbers of effective papillae formation were observed in resistant lines, including Mardler, Ulka/8*Cc, Mardler/7* Bainong3217F5) Pm16 and Pm16/7* Beijing837F5 . Paralleled (H202) accumulation was found in effective papillae and in cytosolic vesicles near the papillae in both susceptible and resistant wheat lines, suggesting the important role of effective papilla formation in general plant defense to powdery mildew. Among resistant wheat lines, hypersensitive cell death in Mardler and Ulka/8*Cc was detected earlier than that in Pm16 and Pm16/7* Beijing837F5 , and was associated with (H202) accumulation throughout attacked epidermal cells. Interestingly, resistance but not HR was mediated by the Pm2 gene in the Mardler/7* Bainong3217F5 line, suggesting an HR-independent defense pathway. Since effective papillae and HR did not occur in the same cells, the papilla deposition may be independent of the HR response. However, both defense mechanisms were associated with high (H202) accumulation. In wheat-powdery mildew incompatible interactions, the failure of the papilla response may be a prerequisite for the expression of HR.