Two sides of a leaf blade: Blumeria graminis needs chemical cues in cuticular waxes of Lolium perenne for germination and differentiation
- 381 Downloads
Plant surface characteristics were repeatedly shown to play a pivotal role in plant–pathogen interactions. The abaxial leaf surface of perennial ryegrass (Lolium perenne) is extremely glossy and wettable compared to the glaucous and more hydrophobic adaxial surface. Earlier investigations have demonstrated that the abaxial leaf surface was rarely infected by powdery mildew (Blumeria graminis), even when the adaxial surface was densely colonized. This led to the assumption that components of the abaxial epicuticular leaf wax might contribute to the observed impairment of growth and development of B. graminis conidia on abaxial surfaces of L. perenne. To re-assess this hypothesis, we analyzed abundance and chemical composition of L. perenne ab- and adaxial epicuticular wax fractions. While the adaxial epicuticular waxes were dominated by primary alcohols and esters, the abaxial fraction was mainly composed of n-alkanes and aldehydes. However, the major germination and differentiation inducing compound, the C26-aldehyde n-hexacosanal, was not present in the abaxial epicuticular waxes. Spiking of isolated abaxial epicuticular Lolium waxes with synthetically produced n-hexacosanal allowed reconstituting germination and differentiation rates of B. graminis in an in vitro germination assay using wax-coated glass slides. Hence, the absence of the C26-aldehyde from the abaxial surface in combination with a distinctly reduced surface hydrophobicity appears to be primarily responsible for the failure of normal germling development of B. graminis on the abaxial leaf surfaces of L. perenne.
KeywordsBlumeria Lolium Epicuticular wax n-Hexacosanal Pre-penetration (fungal development)
Appressorial germ tube
Secondary germ tube
The authors thank Olga Frank and Nadine Geudner for excellent technical assistance, Vanessa Zabka, Tanja Gulder and Gerhard Bringmann for the synthesis of n-hexacosanal. This project was financially supported by the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 567).
- Carver TLW, Thomas BJ (1990) Normal germling development by Erysiphe graminis on cereal leaves freed of epicuticular wax. Plant Pathol 39:375–376Google Scholar
- Carver TLW, Ingerson SM, Thomas BJ (1996) Influences of host surface features on development of Erysiphe graminis and Erysiphe pisi. In: Kerstiens G (ed) Plant cuticles. BIOS Scientific Publishers, Oxford, pp 255–266Google Scholar
- Ellingboe AH (1972) Genetics and physiology of primary infection by Erysiphe graminis. Phytopathology 62:401–406Google Scholar
- Hall DM, Burke W (1974) Wettability of leaves of a selection of New Zealand plants. N Z J Bot 12:283–298Google Scholar
- Holloway PJ (1970) Surface factors affecting the wetting of leaves. Pest Manag Sci 1:156–163Google Scholar
- Knoll D, Schreiber L (2000) Plant–microbe interactions: wetting of ivy (Hedera helix L.) leaf surfaces in relation to colonization by epiphytic microorganisms. Microb Ecol 41:33–42Google Scholar
- Sant FI (1969) A comparison of the morphology and anatomy of seedling leaves of Lolium multiflorum Lam. and Lolium perenne L. Ann Bot 33:303–313Google Scholar
- Stosch AK, Solga A, Steiner U, Oerke EC, Barthlott W, Cerman Z (2007) Efficiency of self-cleaning properties in wheat (Triticum aestivum L.). J Appl Bot Food Qual 81:49–55Google Scholar
- Vogg G, Fischer S, Leide J, Emmanuel E, Jetter R, Levy AA, Riederer M (2004) Tomato fruit cuticular waxes and their effects on transpiration barrier properties: functional characterization of a mutant deficient in a very-long-chain fatty acid β-ketoacyl-CoA synthase. J Exp Bot 55:1401–1410PubMedCrossRefGoogle Scholar