Assessment of Relationship between Downy Mildew Disease Resistance and Biochemical Markers in Pearl Millet (Pennisetum glaucum L.) Entries

The present investigation was carried out for screening of pearl millet entries with respect to downy mildew disease. Study of isozymes (peroxidase, esterase and polyphenol oxidase) and stress proteins was carried out at 30 and 50 days growth stages. Amongst the two stages, 50 days stage was found more appropriate for screening of entries of pearl millet against downy mildew. Quantitative difference in banding of peroxidase was observed at this stage amongst the resistant and susceptible entries. There was presence of unique isoforms with Rm values 0.29, 0.58 and 0.15 with dark, medium and varying intensity, respectively in most of the resistant entries. Esterase banding pattern revealed both quantitative as well as qualitative differences amongst the entries. Moderate to high intensity isoforms were found in resistant entries whereas susceptible entries showed more number of isoforms. Two unique isoforms were present in most of the resistant entries, one (Rm 0.39) with dark intensity at 50 days growth stage and other (Rm 0.75) having varying intensity at 30 days growth stage. Polyphenol oxidase failed to distinguish amongst the resistant and susceptible entries. Leaf protein banding pattern at both stages can be useful provided low intensity bands are considered. The specific differentiation in peroxidase and esterase isozyme pattern can be useful for screening of genotypes against downy mildew resistance.