BREEDING PEARL MILLET (Pennisetum glaucum (L) R. BR.) FOR DOWNY MILDEW RESISTANCE AND IMPROVED YIELD IN BURKINA FASO
ABSTRACT
Downy mildew caused by Sclerospora graminicola (Sacc.) Schroet is the major disease of pearl millet in the Sahel West Africa (SWA). It causes substantial yield loss in open pollinated varieties (OPVs) and constitutes a serious threat to single cross F1 hybrids of pearl millet. Participatory rural appraisal (PRA) was conducted in the Sahel and North-Sudan zones in Burkina Faso to identify farmers’ production constraints and varietal preferences of pearl millet. An on-farm survey was conducted to assess downy mildew incidence on yield. Pathogen variability of S. graminicola was assessed using host differential screening. Two hundred S2 progenies of two cytoplasmic male sterility maintainer lines (B-lines) were screened for downy mildew reaction using three pathotypes of S. graminicola, and genotyped using 30 simple sequence repeat (SSR) markers to determine markers associated with downy mildew resistance. Eighteen diverse landraces were crossed to the two male sterile lines to generate 36 top-cross hybrids by line by tester mating design. Top-cross hybrids, the landraces, four top-cross hybrid checks and two improved OPV checks were evaluated using alpha lattice design, three replications in three locations across the Sahel and North-Sudan zones of Burkina Faso to estimate heterosis and identify high yielding and stable hybrids. The PRA indicated that farmers’ ideal pearl millet variety combines tolerance to drought, resistance to Striga head miner and downy mildew with morphological traits such as compactness of panicle, non-bristle panicle, earliness, medium plant height, and large grain size. The field survey revealed moderate to high downy mildew incidence on landraces in farmers’ fields. Host differential characterization of S. graminicola isolates revealed three virulence groups.
The progeny CIVAREX-S2-145 was resistant to all the three pathotypes, 14 other S2 progenies were resistant to two pathotypes, and 42 S2 progenies showed specific resistance. Six SSR markers were significantly associated with downy mildew resistance. General combining ability (GCA) was significant for all the traits except grain yield. Positive better parent heterosis (2 – 98%), standard OPV heterosis (2 – 21%) and standard hybrids heterosis (1 – 12%) were observed for gain yield. The hybrid MS_SOSAT/PE03012 was the highest yielding with 2291 kg/ha, 12% standard hybrid heterosis, 21% standard OPV heterosis and 98% better parent heterosis. The hybrid MS_CIVAREX/IKMP5 was stable across environments and MS_SOSAT/Indiana05 was the ideal hybrid combining yield performance and stability across environments.
The results from this study provide useful information to pearl millet breeders developing downy mildew resistance breeding, top-cross hybrid and inbred line development, and markers assisted selection.