Serodiagnosis of pearl millet resistance to downy mildew by quantitating cell wall P/HRGP using polyclonal antiserum Pab-P/HRGP

Proline/hydroxyproline-rich glycoprotein (P/HRGP) level in pearl millet genotypes resistant to downy mildew increase after inoculation with the oomycete pathogen Sclerospora graminicola. Using purified P/HRGPs from pearl millet cell walls, polyclonal antibodies (Pab-P/HRGP) were raised in rabbit. Based on this antiserum, an enzyme immunoassay was developed that displays a linearity detection range from 0.01 to 10 μg P/HRGP. Western blot analysis, confirming the induction of three marker P/HRGPs in the infected resistant genotype, and immunocytochemical studies on P/HRGP localization either in epidermal peelings or in suspension-cultured cells demonstrated the specificity of the antiserum. Besides its characterization, Pab-P/HRGP was employed to screen various genotypes of pearl millet for fast, sensitive and specific detection of induced P/HRGPs upon infections. The results presented are discussed with presumed importance to downy mildew disease and the use of this new antiserum in pearl millet screening for disease resistance.