Effect of induced resistance on the efficiency of powdery mildew haustoria in wheat and barley

Mechanisms involved in control of Blumeria graminis f.sp. hordei in barley treated with mycelial extracts from cultured fungi

“…An enlarged extrahaustorial matrix is a sign of maturity, and is associated with reduced capacity to take up nutrients from the cell (Hirata, 1967). If the haustorium is inefficient in nutrient uptake, it will also be unable to support further growth, such as new mycelia, secondary haustoria and conidia production (Stenzel et al, 1985). In the present investigation, primary haustoria in mycelial extract-treated leaves showed no sign of enlargement of the extrahaustorial membrane 72 h after inoculation (data not shown).…”

“…In the present investigation, primary haustoria in mycelial extract-treated leaves showed no sign of enlargement of the extrahaustorial membrane 72 h after inoculation (data not shown). However, it may be too early to expect the haustorium to show signs of ageing, as haustoria with enlarged extrahaustorial membranes on B. subtilis-treated leaves were not observed until 96 h after inoculation (Stenzel et al, 1985). Both hyphal lengths and number of hyphal appressoria on mycelial extract-treated leaves were almost halved compared with the control treatment.…”

“…They found that the protection involved increased papilla formation and enhanced activity of phenylalanine ammonia lyase, the key enzyme in phenolic compound synthesis. Stenzel et al (1985) did not find any effects on germination or appressoria formation by wheat powdery mildew after treating wheat test plants with a culture filtrate from B. subtilis, even though they obtained high levels of protection. Early haustorium formation was also unaffected.…”

“…Only a few studies have investigated microbial components as biopesticides in monocotyledonous plants. In all cases, the proposed mode of action has been induced resistance (Schönbeck et al ., 1980;Schönbeck et al ., 1982;Stenzel et al ., 1985;Schönbeck & Dehne, 1986;Reglinski et al ., 1990;Reglinski et al ., 1994a;Reglinski et al ., 1994b).…”

Variation over time and environments in resistance to Erysiphe graminis hordei in samples from a barley germplasm collection

“…In the case of disease resistances slightly different pathogen or environmental pressures can modify reactions to a given pathogen . An example is the recently described phenomenon of `induced resistance', which has been reported for a number of crops (Stenzel et al ., 1985 ;Cho & SmedegaardPetersen, 1986 ;Dolan et al ., 1986) . The balance of micronutrients in soils and their uptake are also known to affect responses to pathogens .…”