Effect of varying humidities in vitro upon the production and germination of mildew conidia from Erysiphe graminis f. sp. tritici
1993
Friedrich, S. (Technische Univ. Braunschweig, (Germany). Inst. fuer Mikrobiologie) | Boyle, C.
The influence of relative humidity upon the conidiogenesis, germination rate, germ tube growth and appressoria formation of mildew on wheat (Erysiphe graminis f. sp. tritici) was investigated under various incubation humidities in climate chambers. Conidiogenesis at high relative humidity resulted in 7 % more conidial water content than at dryer conditions. The largest aliquote of turgid conidia was detected after an incubation on slides at 97 % relative humidity. Higher humidity during incubation increased the number of burst conidia; at reduced humidity levels the amount of shrunken conidia increased. The humidity level during conidiogenesis had no influence on the germination rate, however, it effected germ tube growth. Conidia formed under dryer conditions generated considerably longer germ tubes at 97 % incubation humidity than those raised under moist conditions. Incubation at 92 % relative humidity and below already after 2 h restricted further germ tube growth and appressoria development. The optimum incubation humidity for germ tube growth and appressoria development for conidia produced under dryer conditions (97 %) was somewhat lower than for the wetter variant. Differences in germination and water capacity of conidia formed under various growth conditions are discussed with respect to infectivity under field conditions, epidemiological consequences and their relevance for the stimulation of field infections
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