Encasement of Erysiphe graminis haustoria after treatment with bromuconazole
1996
Mangin-Peyrard, M. | Pépin, R.
Preventive application of bromuconazole caused reduction in size and increased encasement rate of haustoria of Erysiphe graminis DC. For example, seven days after inoculation. 60 and 70% of haustoria had been encased in leaves treated with 8 mg litre-1 and 16 mg litre-1 respectively; the average length of the digitations was 8-10 micrometers in treated cells compared to 24 micrometers in untreated cells. The encasement process extended from the neck region to the whole haustorium. Haustorial bodies from treated plants had electron-dense cytoplasm and their organelles were more difficult to identify than in control plants. Extra-haustorial matrix was reduced to an unusually thin, osmiophilic pellicle, surrounded by abundant heterogeneous encasement material. Curative treatment induced similar changes, especially in the margin of the colonies. In the centre of the colony, haustoria were less affected by the fungicide; deposition of collar-like material, modification of extrahaustorial matrix and membrane and accumulation of plant cytoplasm around the digitations resulted in an intermediate, 'swollen' state of digitate haustoria. The possible pathway of encasement events is discussed.
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