South African Journal of Plant and Soil

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Inheritance of resistance to Ug99 stem rust pathogen in selected barley lines

Mercy N Wamalwa, Ruth Wanyera, Peter N Njau, Michael A Okiror, James O Owuoche


Stem rust (Puccinia graminis tritici) race Ug99 is a devastating disease of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). Barley is the world’s fourth most important cereal crop after wheat, maize (Zea mays L.) and rice (Oryza sativa L.). The seedlings of F2 populations were inoculated 7–10 d after planting and when the first leaf was fully emerged (Feekes stage 1). The observed resistant (R):susceptible (S) ratio  f the F2 populations HKBL-1385-13 × 08-UT-86 (χ2 0.05 = 0.480, P ≥ 0.488), HKBL-1385-13 × 09-N2-19 (χ2 0.05 = 0.641, P ≥ 0.424), ND2649 × 09-AB-78 (χ2 0.05 = 1.05, P ≥ 0.309) and ND25882 × 09-AB-78 (χ2 0.05 = 3.599, P ≥ 0.058) exhibited Mendelian segregation of 3R:1S suggesting that the resistance is conferred by major genes. In addition, F2 populations derived from the crosses Karne × 09-N2-19 (χ2 0.05 = 1.343, P ≥ 0.246), Nguzo × 09-AB-78 (χ2 0.05 = 0.429, P ≥ 0.512), ND26249 × 09-N2-52 (χ2 0.05 = 2.576, P ≥ 0.111) and ND25882 × 09-AB-78 (χ2 0.05 = 0.980, P ≥ 0.322) conformed to a phenotypic ratio of 9:7 indicating that there are genes modifying the resistance to Ug99. The results of this study suggest that there are valuable major genes for stem rust resistance that could be used to improve susceptible barley and wheat germplasm.

Keywords: barley, Mendelian, stem rust, Ug99

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