Characterization of Downy Mildew Resistance in Pearl Millet
1997
Thakur, R P | Rao, V P | Singh, S D | Navi, S S
Sixty-one pearl millet (Pennisetum glaucum) genotypes from diverse geographical origins identified as downy mildew (Sclerospora graminicola) resistant in several field tests at IAC and other locations in India and Africa were evaluated against five host-specific pathotypes and a field population of S. graminicola, referred to as pathotype 6. Pot-grown seedlings of all the pearl millet genotypes, were spray-inoculated with a sporangial suspension (1 times 10 super(5) sporangia ml super(-1)) of each pathotype in a replicated experiment in a glasshouse. Observations were recorded for latent period and disease incidence. Host resistance index (HRI) is suggested as a measure of resistance stability, and was calculated as [1 + (ab super(-1))] super(-1), where a = disease incidence (%), and b = latent period (day). There were highly significant (P < 0.001) effects of host genotype, pathotype, and their interaction on HRI. A number of genotypes were disease free to different pathotypes; IP 18292 was disease free from all six pathotypes. An additional 15 genotypes showed < 10% incidence to all six pathotypes. These genotypes with HRI values of 0.69 to 0.94 and are the best available sources of resistance. Eight genotypes (IP 5272-1, IP 18296, IP 18297, P 536-2, P 1564, P 2895-3, P 3281-1, and 700481-21-8) that showed differential reactions to six pathotypes can be utilized for characterizing S. graminicola isolates.
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