Evaluating Adult Plant Resistance to Leaf Rust and Stem Rust of Wheat in a Newly Developed Recombinant Inbred Line Population

Leaf rust caused by Puccinia triticina and stem rust by P. graminis are the most destructive diseases of wheat (Triticum aestivum L.) resulting in substantial yield losses globally. New and aggressively virulent pathotypes are emerging to overcome effective resistance in existing wheat cultivars, particularly when resistance is conferred by race-specific genes. A continuous search for new sources of effective rust resistance genes is necessary to develop improved wheat varieties with stable and durable resistance. The aim of this study was to investigate the inheritance of adult-plant resistance in a recombinant inbred line (RIL) population of a cross between ‘Popo’ and ‘Kariega’, and to identify wheat breeding lines possessing both leaf and stem rust resistance. A panel of 179 RILs, two parental varieties and three checks ‘Gariep’, ‘SST88’ and ‘Morocco’ were evaluated in the field, across four diverse environments, for resistance to leaf rust and stem rust diseases. Disease response ranged from highly resistant to highly susceptible reactions with severity scores reaching 100%. Analysis of variance indicated highly significant (P < 0.001) differences among the tested RILs for both pathogens across the testing environments. The broad sense heritability estimates were 0.53 and 0.77 for leaf rust and stem rust, respectively. Twenty-six RILs had average severity scores that were better than the parental varieties, and showed higher levels of resistance to both pathogens. Due to the moderate to high heritability estimates for leaf rust and stem rust resistance, the use of the newly developed RILs in the genetic background of Popo/Kariega enhances pre-breeding for rust resistance against the two diseases. Genes controlling such resistance should be explored to elucidate and exploit quantitative trait loci (QTLs) for breeding.