ARS | Publication request: Detection, seed transmission, and control of Hyaloperonospora camelinae on Camelina sativa (L.) in Washington State

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2012
Publication Date: July 1, 2012
Citation: Babiker, E.M., Hulbert, S.H., Paulitz, T.C. 2012. Detection, seed transmission, and control of Hyaloperonospora camelinae on Camelina sativa (L.) in Washington State. Phytopathology. 102:S4.8.

Technical Abstract: Camelina (Camelina sativa [L.] Crantz) plants with symptoms of downy mildew were obtained from three different locations in Washington State. Based on PCR and sequencing of the ITS1-5.8S-ITS2 region, the causal pathogen was identified as Hyaloperonospora camelinae. The PCR primers consistently amplified 699 bp bands from the infected plants, but not from the healthy plants. A comparison of the sequences with those in GenBank revealed 100% sequence similarity to H. camelinae. Growth and development of the H. camelinae was observed in different tissues using light and scanning electron microscopy (SEM). Light microscopic observation revealed the presence of oospores in the infected leaves and SEM revealed the presence of conidia and conidiophores on the seed surface. To determine whether downy mildew is a seed-transmitted disease, seeds collected from infected plants were planted in potting mixes maintained in a growth chamber. Disease symptoms were observed in 96% of the seedlings compared to 3% of the seedlings grown from seed from healthy plants, which indicates that downy mildew of camelina is a seed-transmitted pathogen. Seeds treated with mefenoxam, a fungicide specific for Oomycetes, significantly reduced the incidence of the disease.