In many production areas, barley (Hordeum vulgare L.) is attacked by the leaf rust pathogen (Puccinia hordei Otth), a basidiomycetous fungus that reduces both its yield and quality. Many leaf rust resistance genes, known as reaction to P. hordei (Rph) genes, have been described in barley. To differentiate genetic variants for virulence in pathogen populations, plant pathologists use differentials (i.e., sets of host lines carrying different resistance genes). The sources of Rph1–15 were derived from cultivars, landraces, and wild barley (H. vulgare ssp. spontaneum K. Koch) accessions with diverse geographic origins and agromorphological traits. Ideal differential sets comprise single‐gene lines backcrossed to a single adapted accession that is susceptible to all known races of a pathogen. In this study, sources of Rph1–15 and other Rph gene donors were backcrossed to the susceptible barley cultivar Bowman and then genotyped to characterize the chromosomal positions and sizes of introgressions. Overall, 95 Bowman introgression lines for leaf rust resistance were developed and characterized for their rust phenotypes and genotypes. A single line was selected to represent each of the 15 Rph genes for use as the new barley leaf rust differential set. The existence of possible new resistance genes in the studied germplasm was postulated. The new Bowman Rph1–15 differential lines will facilitate the efficient virulence phenotyping of P. hordei and serve as valuable genetic stocks for Rph gene stacking and cloning in barley.

DiVerent production environments are being adopted by farmers. Therefore, allocation of resources to breeding research that targets diVerent production environments should be continuously assessed. Agronomists should conduct extensive hybrid £ production environment interaction research before recommending breeders to conduct separate breeding programs for each production environment. The lack of interactions between genotypes and production environments (e.g., tillage) would not justify conducting separate breeding programs and duplicating breeding resources. On the other hand, separate breeding programs would be necessary if cultivar rankings diVer. The purpose of this paper is to review the available literature on experiments designed to test genotype £ tillage interactions (GT) in maize (Zea mays L.). No-till system (NT) and conventional till system (CT) were utilized as examples of diVerent production environments. The majority of experiments reviewed showed that there is no need to develop cultivars speciWc to NT because the cultivars that were developed under CT systems performed relatively the same under NT. The magnitude of GT interactions found was very small to expect better cultivars from breeding under NT. Additional research is needed to conWrm these conclusions, especially when applied to other production environments (e.g., development of cultivars under organic conditions). Scientists should evaluate genotype by tillage interactions before investing additional resources in breeding for those speciWc target environments. Top yielding genotypes seem be consistent across years, locations, inputs; and most of the present evidence suggests that breeding for speciWc till systems is not necessary.