Characterization of Blast Resistance in a Diverse Rice Panel from Sub-Saharan Africa

Area of Science:

• Plant Pathology
• Genetics
• Agricultural Science

Background:

• Sub-Saharan Africa faces increasing rice demand, yet blast disease significantly impacts production.
• Understanding blast resistance in African rice cultivars is crucial for growers and breeders.
• Characterizing genetic resistance is key to developing resilient rice varieties.

Purpose of the Study:

• To characterize blast resistance in African rice genotypes using molecular markers.
• To evaluate the effectiveness of known rice blast resistance (Pi) genes against African isolates of Magnaporthe oryzae.
• To identify specific Pi genes associated with resistance or susceptibility in African rice.

Main Methods:

• Genotyping of 240 African rice cultivars using 21 molecular markers for known Pi genes.
• Greenhouse assays challenging 56 representative genotypes with 8 virulent African M. oryzae isolates.
• Statistical analysis (stepwise regression) to correlate Pi genes with blast severity.

Main Results:

• Rice genotypes were grouped into five blast resistance clusters (BRC) based on molecular markers.
• Pi50 and Pi65 genes were significantly associated with reduced foliar blast severity.
• Pik-p, Piz-t, and Pik genes were linked to increased susceptibility; IRAT109 (Piz-t) showed varied resistance, while Basmati cultivars were highly susceptible.

Conclusions:

• Most tested Pi genes were ineffective against African blast pathogen collections.
• Pyramiding Pi2/9 and Pi65 genes may confer broad-spectrum resistance.
• Further gene mapping with local pathogen isolates is recommended for deeper insights into genomic regions for blast resistance.