Effects of calcium nitrate and chlortetracycline on papilla formation, ml-o resistance and susceptibility of barley to powdery mildew

Tissue-Specific Expression of Germin-Like Oxalate Oxidase during Development and Fungal Infection of Barley Seedlings

“…On the other hand, H 2 O 2 produced by the degradation of oxalic acid by oxalate oxidase can be used as a substrate by peroxidases that are induced during the development of powdery mildew in wheat and barley (Schweizer et al, 1989;Thordal-Christensen et al, 1992;Boyd et al, 1994). In this case, the induction of oxalate oxidase activity can contribute to the ability of the infected tissue to lignify and to the formation of cell wall appositions (papillae) (Gold et al, 1986).…”

The Barley mlo-gene: an important powdery mildew resistance source

“…Skou et al [51] showed a significant difference in initiation of appositions (haloes and papillae) between a resistant and a near isogenic susceptible barley line, and concluded that the early formation of papilla was responsible for mlo resistance. Alterations in papilla deposition have also been shown in mlo resistant barley coleoptiles where papillae were initiated 60 minutes before attempted penetration by the fungus, in contrast to susceptible coleoptiles where they were initiated 40 minutes after attempted penetration [21]. The importance of timing of papilla deposition in relation to attempted penetration has also been supported by inhibitor studies, in which a delay in papillae formation in treated coleoptiles of an mlo resistant barley line was observed coincidentally with an increase in fungal infection [10,21].…”

“…Rapid papilla formation in mlo resistant barley has been suggested as one mechanism involved in resistance [10,21,51]. Skou et al [51] showed a significant difference in initiation of appositions (haloes and papillae) between a resistant and a near isogenic susceptible barley line, and concluded that the early formation of papilla was responsible for mlo resistance.…”

“…Increased papilla size and frequency at attempted penetration sites also correlates with mlo resistance [21,49,51,53,58]. The diameters of papillae have been measured as almost two times larger in resistant lines compared to susceptible lines at the time of fungal penetration e.g.…”

“…The deposition rate of callose and the final amount of callose in papillae have also been regarded as important to the effectiveness of papillae in mlo resistant barley [2,10,21,35,49,54]. Callose is synthesised by the plasma membrane bound 1,3-β-glucan synthase [32,39].…”