Pathotype variation of barley powdery mildew in Western Australia

Barley powdery mildew caused by the fungus Blumeria graminis f. sp. hordei (Bgh) has emerged as the most damaging disease of barley in Western Australia (WA). Many of the available cultivars display high levels of disease in the field when climatic conditions are conducive. As a result, fungicides have become the main method of disease control in the last 10 years. Different types and sources of genetic disease resistance are available but to optimise their deployment it is necessary to evaluate the spectrum of pathotypes present in the pathogen population. Sixty isolates of Bgh were collected in the 2009 season from 9 locations, single spored and characterised by infection on reference barley lines and cultivars. Eighteen unique pathotypes were resolved. Virulence against many of the R-genes in the reference lines was present in at least one pathotype. Isolates were virulent against 16 out of a total of 23 resistance gene combinations. Undefeated resistance genes included the major R-genes Mla-6, Mla-9, Ml-ra and the combinations of Mla-1 plus Mla-A12 and Mla-6 plus Mla-14 and Mla-13 plus Ml-Ru3 together with the recessive resistance gene mlo-5. There was significant pathotype spatial differentiation suggesting limited gene flow between different regions with WA or localised selection pressures and proliferation. On the basis of the results we recommend a number of strategies to manage powdery mildew disease levels within WA

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

Novel genes from wild barley hordeum spontaneum for barley improvement

Narrowing genetic basis is the bottleneck for modern plant improvement. Genetic variation in wild barley Hordeum spontaneum is much greater than that of either cultivated or landrace H. vulgare gene pool. It represents a valuable but underutilised gene pool for barley improvement as no biological isolation barriers exist between H. spontaneum and cultivated barley. Novel sources of new genes were identified from H. spontaneum for yield, quality, disease resistance and abiotic tolerance. Quantitative trait loci (QTLs) were mapped to all barley chromosomes. A QTL on chromosome 4H from the wild barley consistently increased yield by 7.7% across six test environments. Wild barley H. spontaneum was demonstrated as key genetic resource for drought and salinity tolerance. Two QTLs on chromosomes 2H and 5H increased grain yield by 12–22% under drought conditions. Several QTL clusters were present on chromosomes 1H, 2H, 4H, 6H and 7H from H. spontaneum for drought and salinity tolerance. Numerous candidate genes were identified to associate with tolerance to drought or salinity, and some of the candidate genes co-located with the QTLs for drought tolerance. QTLs/genes for resistance to powdery mildew, leaf rust and scald were mapped to all chromosomes. Scald resistance was found in at least five chromosome locations (1HS, 3H, 6HS, 7HL and 7HS) from H. spontaneum, and simple molecular markers were developed to accelerate transferring of these genes into cultivated barley. Novel beta-amylase allele from H. spontaneum was used to improve barley malting quality. Advanced backcross QTL provides an efficiency approach to transfer novel genes from H. spontaneum to cultivated barley