Identification of barley powdery mildew resistances in gene bank accessions and the use of gene diversity for verifying seed purity and authenticity

Abstract

Human activities including those in crop gene banks are subject to errors, especially during seed multiplication and maintenance of seed germination. Therefore, the most serious problem of gene banks is authenticity of the accessions and their genotypic purity. There are many methods for determining the identity of varieties, but comparisons between current data and past records are not easy since the latter are often missing. Breeding barley resistant to powdery mildew caused by Blumeria graminis f. sp. hordei (Bgh) was traditionally based on incorporating major genes into new varieties and the results have been published. Our goal was to identify resistance genes to powdery mildew in accessions of the Czech spring barley core collection and compare these data with earlier information to establish the authenticity of the accessions. Two hundred and twenty-three accessions of the collection including 665 single plant progenies were tested. Sixty-four selected reference isolates of Bgh representing the world diversity of the pathogen were used for resistance tests. Twenty-two known resistance genes were postulated either separately or in combinations. In the collection, 151 homogeneous accessions were found, but the resistances of nine of them were inconsistent with published data and in 12 accessions their authenticity is doubtful. The remaining 72 accessions were heterogeneous and comprised 176 resistance genotypes, 54 of which were probably mechanical admixtures of other varieties. There are several pathogens of cereals, e.g. rusts and mildews, against which many resistance genes in host crops have also been exploited. Knowledge of these resistances can assist in maintaining pure and genuine stocks in gene banks. Seed purity and the authenticity of accessions can subsequently be checked with more advanced methods.

Specific Resistance of Barley to Powdery Mildew, Its Use and Beyond: A Concise Critical Review

“…Many other sets of barley landraces collected in Tunisia [ 52 ], Morocco [ 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ], Australia [ 62 ], China [ 51 ], Greece [ 63 ], Jordan [ 64 ], Latvia [ 65 ], Libya [ 66 ], Spain [ 28 , 67 , 68 ], Turkey [ 69 , 70 ] or from more than one area [ 71 , 72 , 73 , 74 , 75 , 76 , 77 ] have been studied, and numerous known and unknown specific resistances were characterized including accessions resistant to a wide range of pathogen isolates.…”

“…Therefore, when looking for partial resistance [ 110 , 111 , 112 ], the response of specific genes that mask minor resistance genes must be well-characterized and challenged with corresponding virulent isolates prior to investigating the minor genes. Furthermore, knowledge of specific resistances is a valuable tool to establish authenticity and purity of cultivars and to confirm their pedigrees [ 77 ]. Results of testing landraces and wild barley can also be invaluable for mapping and determining the global distribution of native resistances.…”

A novel way to identify specific powdery mildew resistance genes in hybrid barley cultivars

“…Second, some parental cultivars may consist of more than one line. Third, heterogeneity may be caused by out-pollination with different cultivars grown nearby, and fourth, there may be mechanical seed admixtures with other genotypes 30 . These factors could seriously affect the ratios of phenotypes, which may differ from the expected ratios.…”

“…Almost all current barley cultivars contain one or more specific genes 25 , 26 and when looking for partial resistance 27 – 29 specific genes that mask minor resistance genes must be overcome with corresponding virulent isolates of the pathogen. Furthermore, details of the specific resistances in cultivars is a valuable tool to establish their pedigrees, purity and authenticity 30 .…”

A novel resistance against powdery mildew found in winter barley cultivars

“…An example of this problem of characterization can be Abyssinian 1,102, which possesses the powdery mildew resistance gene mlo (Jørgensen, 1992). Since none of the three genotypes found with the same accession name in the Czech spring barley core collection containing mlo (Dreiseitl & Zavřelová, 2018), Abyssinian 1,102 in the core collection is neither genotypically pure nor authentic.…”