Erysiphe graminis, powdery mildew

Expression of peroxidases that catalyze crosslinking reactions can he induced by wounding or infection. Well-documented examples include the production of acidic peroxidase isoenzymes in woimded tissue of tobacco (132), potato (133), and tomato (134), and also in wheat plants infected with the powdery mildew fungus, Erysiphe graminis (135). It is known that peroxidase activity can be induced on wounding of horseradish leaves (56), but other mechanisms of defense in horseradish remain to be demonstrated. 

Wippich, C. and Wink, M. 1985. Biological properties of alkaloids. Influence of quinolizidine alkaloids and gramine on the germination and development of powdery mildew, Erysiphe graminis f. sp. hordei. Experientia 41,1477-1478... 

The active substance FDN (10), N,N-dimethyl-N -(3-chlorophenyl)-guanidine, is a protective and eradicant fungicide of almost the same activity as dinocap against the powdery mildew of cucumber. It is a soil fungicide, the active substance being absorbed by the roots of the plant. It also has a satisfactory effect against Erysiphe graminis (Melnikov et al., 1974). Its acute oral lDj is 420 mg/kg for rats. 

The main application of BTH is to control powdery mildew in wheat and barley. BTH is an important defense response inducer, but it did not affect the pathogen metabolism like fungicides. In order to determine whether BTH played a role in SAR, a susceptible wheat cultivar was infected with Erysiphe graminis f. sp. triticL, then sprayed with BTH ten days after inoculation. A hypersensitive response was successfully initiated. This was a clear... 

Powdery mildew infection of wheat leaves was accompanied by increased production of cuticular waxes but did not result in consistent changes in the proportions of the component fractions. The amount of wax present per unit area of leaf surface of healthy plants was greater in resistant than in susceptible cultivars, while the partially resistant cultivar investigated was intermediate in this respect. Although exudates from Erysiphe graminis f sp. hordei have been shown to have esterase and cutinase activity which is likely to be of importance in the initiation of infection (Kunoh et a/., 1990 Nicholson et al, 1993), the present results support other evidence for the importance of the thickness of the cuticular wax layer in resistance to powdery mildew. 

Walters DR, Wilson PWF, Shuttleton MA (1985) Relative changes in levels of polyamines and activities of biosynthetic enzymes in barley infected with powdery mildew fungus, Erysiphe graminis DC. Ex Merat f. sp. Hordei Marchal. New Phytol 101 695-705... 

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