Pearl millet (Pennisetum glaucum) stands sixth among the most important cereal crops grown in the
semi-arid and arid regions of the world. The downy mildew disease caused by Sclerospora graminicola, an
oomycete pathogen, has been recognized as a major biotic constraint in pearl millet production. On the
other hand, basidiomycetes are known to produce a large number of antimicrobial metabolites, providing
a good source of anti-oomycete agrochemicals. Here, we report the discovery and efficacy of a compound,
named G_app7, purified from Ganoderma applanatum on inhibition of growth and development of
S. graminicola, as well as the effects of seed treatment with G_app7 on protection of pearl millet from
downy mildew. G_app7 consistently demonstrated remarkable effects against S. graminicola by recording
significant inhibition of sporangium formation (41.4%), zoospore release (77.5%) and zoospore motility
(91%). Analyses of G_app7 compound using two-dimensional nuclear magnetic resonance spectroscopy
and liquid chromatography-mass spectrometry revealed its close resemblance to metominostrobin, a
derivative of strobilurin group of fungicides. Furthermore, the G_app7 was shown to stably maintain the
inhibitory effects at different temperatures between 25 and 80 C. In addition, the anti-oomycete activity
of G_app7 was fairly stable for a period of at least 12 months at 4 C and was only completely lost after
being autoclaved. Seed treatment with G_app7 resulted in a significant increase in disease protection
(63%) under greenhouse conditions compared with water control. The identification and isolation of this
novel and functional anti-oomycete compound from G. applanatum provide a considerable agrochemical
importance for plant protection against downy mildew in an environmentally safe and economical
manner.