Influence of Different Irrigation Regimes on Carpogenic Germination of Sclerotia of Sclevotinia sclerotiorum

The effects of irri ga lion level. irriga lion interval, length of irrigation break and of soil type on apothecial production. a pothecia l survival and sclerotial survival of Sclel"olill ia sclero/forum were studied in field experiments in 1991 a nd 1992. The experimenta l arca was sown wi th spring rapeseed and na tu rally produced sclerotia were placed I cm deep in the soil. Apothecia production started after 25- 30 days of continuous soil moisture and was strongly influenced by the irrigation rcgime. Apothecia development was delayed if an irrigation break occurred before the sta rt of apOlhecia producti on. The delay was approx imately of thc same length as thc irriga tion brea k. A high irriga tion level caused more abundant apothecia product ion in the sand than in the loam. while at a low irrigation level. more apothecia were produced in the loam than in the sand. The maximum lifespan of apothecia was 33 days which was measured in the sand irriga ted at 5 mm/day. The length of the moist peri od needed fo r carpogenic germination and the inflllence of dry periods are shown in thi s study and can be used wben predicting the start of " pot hecia development. It is a lso shown that both soil type. amou nt ofirrigatiol1 or rainfall ~lI1d its dist ribution must be considered when estimating the nllmber of apothecia and llpothecia longevity.