3.4.65
PRELIMINARY RESULTS ON THE CULTIVAR RESISTANCE OF FALSE FLAX (CAMELINA SATIVA) AGAINST DOWNY MILDEW, PERONOSPORA PARASITICA (SYN. P. CAMELINA)

I FOLLER, M HENNEKEN and VH PAUL

Universitat-Gesarnthochschule Paderborn, Fachbereich Agrarwirtschaft, Ubecker Ring 2, D-59494 Soest, Germany

Background and obiectives
The objectives of the study presented here were to evaluate the disease susceptibility of false flax under field conditions, to identify and isolate the main pathogens and, to supply infection methods for breeders to use in disease resistance breeding. According to literature downy mildew is one of the most important and frequent diseases in false flax [1]. Therefore 10 cultivars/breeding lines were assessed for disease resistance against downy mildew under laboratory conditions. Furthermore studies on the seedborne nature and production of persistent stages (oospores) of downy mildew in false flax are in progress.

Materials and methods
For laboratory studies, plants of the 10 cultivars and breeding lines were grown in multi-pot plates in the greenhouse until they reached the cotyledon, two leaf and, four leaf stage. At these growth stages plants were spray inoculated with a conidial suspension of two different downy mildew isolates (10,000 conidia/ml) and transferred to a climatic chamber. The plants were then covered with plastic lids to keep a high relative humidity (>95%) and placed under neon light with 3.500 lux, a temperature of 17/10C (day/night) and, 14/10 h (light/dark) photoperiod. The assessment for disease incidence was carried out after 7 (cotyledon stage) and 10 days (two leaf and four leaf stage) after inoculation, respectively. The assessments were done according to Klodt-Bussmann [2].

Results and conclusions
The inoculation with downy mildew showed that all false flax cuftivar breeding lines were very susceptible in the cotyledon stage and that the susceptibility decreased with increasing plant age. At the cotyledon stage nine of the 10 cultivars/breeding lines showed an average assessment rate of about 5 (5=75-100% of the leaf area infected) and one an average assessment rate of about 4 (4=50-<75% of the leaf area infected). At the two and four leaf stage the reaction of tlne cultivars/breeding lines varied widely.

So far no correlation between laboratory inoculation and natural field infection could be found. This might be due to the reason that downy mildew had a low incidence in the field so far.

Refefences
1.Gustavsson A, 1958. Botaniska Notiser, Vol. 111, Fasc. 1, Lund.
2. Ktodt-Bussmann F, 1995. Dissertation. Friedrich-Wilhelms-Universitat Bonn.