Resistance to Powdery Mildew in Barley Recombinant Lines Derived from Crosses between Hordeum vulgare and Hordeum bulbosum

Barley recombinant lines obtained from crosses and backcrosses of common barley (Hordeum vulgare L.) cultivars Emir and Golden Promise with bulbosus barley grass (H. bulbosum L.) were tested against differential set of 14 Blumeria graminis D.C. Golovin ex Speer f. sp. hordei – synamorph Erysiphe graminis DC. f. sp. hordei Em Marchall isolates, pathogenic fungus causing powdery mildew. Powdery mildew resistance was found in 22 from 24 lines tested. Presence of unknown genes was postulated in 13 lines. In six of these lines the unknown genes were postulated present besides Mla12 allele originated from H. vulgare parent (cv. Emir). The only line resistant to infection, from all isolates used, was 181P94/1/3/1/1/1-2. Four other lines could be considered highly resistant, because they were susceptible to only one powdery mildew isolate. The possibilities to use the hybrid lines with identified resistance to powdery mildew, especially line 181P94/1/3/1/1/1-2 in barley breeding programs were discussed

Characterization of constricted fruit (ctf) Mutant Uncovers a Role for AtMYB117/LOF1 in Ovule and Fruit Development in Arabidopsis thaliana

Pistil and fruit morphogenesis is the result of a complex gene network that is not yet fully understood. A search for novel genes is needed to make a more comprehensive model of pistil and fruit development. Screening for mutants with alterations in fruit morphology generated by an activation tagging strategy resulted in the isolation of the ctf (constricted fruit) mutant. It is characterized by a) small and wrinkled fruits, with an enlarged replum, an amorphous structure of the septum and an irregular distribution of ovules and seeds; b) ectopic carpelloid structures in sepals bearing ovule-like structures and c) dwarf plants with curled rosette leaves. The overexpressed gene in ctf was AtMYB117, also named LOF1 (LATERAL ORGAN FUSION1). AtMYB117/LOF1 transcripts were localized in boundary regions of the vegetative shoot apical meristem and leaf primordia and in a group of cells in the adaxial base of petioles and bracts. Transcripts were also detected in the boundaries between each of the four floral whorls and during pistil development in the inner of the medial ridges, the placenta, the base of the ovule primordia, the epidermis of the developing septum and the outer cell layers of the ovule funiculi. Analysis of changes of expression of pistil-related genes in the ctf mutant showed an enhancement of SHATTERPROOF1 (SHP1) and SHP2 expression. All these results suggest that AtMYB117/LOF1 is recruited by a variety of developmental programs for the establishment of boundary regions, including the development of floral organs and the initiation of ovule outgrowth

Resistance to powdery mildew in selections from barley landraces collected in Greece

Twenty barley (Hordeum vulgare L.) landraces from Greece were tested for resistance to powdery mildew (Erysiphe graminis f. sp. hordei). Landraces originated from a collection of Polish Gene Bank, IHAR Radzików, Poland. Thirteen landraces (65%) expressed resistance reactions and from those 37 single-plant lines were selected. These lines were tested at the seedling stage with 23 differential isolates of powdery mildew. The isolates were chosen according to their virulence spectra as observed on the 'Pallas' isoline differential set and on 8 additional differential cultivars. Fiveteen lines originating from five landraces (4917, 4919, 4926, 4928 and 4935) expressed resistance to all isolates used. In 31 tested lines it was impossible to determine which specific allele or alleles for resistance are present. However, expression of infection types 0, 1 and 2 for the isolates tested indicated that 26 from these lines may have several alleles for resistance. Three different resistance alleles (Mlat and Mla6+ Mla14) were postulated to be present in the lines either alone or in combination with other unidentified genes. Allele Mlat was postulated to be present in 4 and alleles Mla6 + Mla14 were postulated to be present in 2 of the tested lines. The value of landraces for diversification of powdery mildew resistance genes available to barley breeders was discussed.

Resistance to powdery mildew in selections from barley landraces collected in Greece

Twenty barley (Hordeum vulgare L.) landraces from Greece were tested for resistance to powdery mildew (Erysiphe graminis f. sp. hordei). Landraces originated from a collection of Polish Gene Bank, IHAR Radzików, Poland. Thirteen landraces (65%) expressed resistance reactions and from those 37 single-plant lines were selected. These lines were tested at the seedling stage with 23 differential isolates of powdery mildew. The isolates were chosen according to their virulence spectra as observed on the 'Pallas' isoline differential set and on 8 additional differential cultivars. Fiveteen lines originating from five landraces (4917, 4919, 4926, 4928 and 4935) expressed resistance to all isolates used. In 31 tested lines it was impossible to determine which specific allele or alleles for resistance are present. However, expression of infection types 0, 1 and 2 for the isolates tested indicated that 26 from these lines may have several alleles for resistance. Three different resistance alleles (Mlat and Mla6+ Mla14) were postulated to be present in the lines either alone or in combination with other unidentified genes. Allele Mlat was postulated to be present in 4 and alleles Mla6 + Mla14 were postulated to be present in 2 of the tested lines. The value of landraces for diversification of powdery mildew resistance genes available to barley breeders was discussed.

Association mapping of leaf rust response in durum wheat

Resistance to leaf rust (Puccinia triticina Eriks.) is a main objective for durum wheat (Triticum durum Desf.) breeding. Association mapping on germplasm collections is now being used as an additional approach for the discovery and validation of major genes/QTLs. In this study, a collection of 164 elite durum wheat accessions suitable for association mapping has been tested for leaf rust response at the seedling stage and under field conditions (adult plant stage). Seedling tests were carried out with 25 selected isolates from durum wheat, bread wheat and triticale, while field experiments were carried out in artificially inoculated plots in Italy and in Mexico. The collection has been profiled with 225 simple sequence repeat (SSR) loci of known map position and a PCR assay targeting Ppd-A1. Associations showing highly consistent experiment-wise significances across leaf rust isolates and field trials were mainly detected for the 7BL distal chromosome (chr.) region (harbouring Lr14 from cultivar Llareta INIA and QLr.ubo-7B.2 from cultivar Creso) and for two chr. regions located in chrs. 2A and 2B. Additionally, isolate-specific associations and/or associations with smaller effects in the field trials were identified in most of the chromosomes. The chr. 7BL distal region was investigated in detail through haplotyping with 15 SSR markers, revealing that the Creso and Llareta INIA alleles are identical by descent at 6 adjacent SSR loci in the most distal 7BL region spanning 8 cM. Association mapping allowed us to further refine the map location of the Lr14/QLr.ubo-7B.2 resistance gene to the most distal region of the linkage group, tagged by Xcfa2257.2, Xgwm344.2 and Xwmc10. The resistant haplotype is present in a number of accessions (ca. 15% of the accessions included in the collection) from the Italian, CIMMYT and ICARDA breeding programmes. Therefore, this chr. 7BL region can be considered as the most important source of resistance to leaf rust currently exploited by durum breeders in the Mediterranean areas. Furthermore, the field trials at the adult plant stage allowed us to identify marker associations (e.g. chrs. 2BL and 3BS, proximal regions; chr. 7BS, distal region) which suggest the presence of minor QTLs for slow-rusting resistance