Mapping spot blotch & common root rot (causal agent: bipolaris sorokiniana) resistance genes in barley

The fungal pathogen Bipolaris sorokiniana (teleomorph Cochliobolus sativus)causes the foliar disease spot blotch (SB) and the root disease common root rot (CRR). Spot blotch and CRR are serious disease constraints to barley production in warmer growing regions of the world, with estimated yield losses ranging from 30-70% from SB and 15-30% for CRR. Although chemical treatments may assist in controlling spot blotch infections, the most effective and environmentally sound means of control for each disease is breeding for varieties with natural resistance. In Australia, no commercially available varieties offer resistance to either SB or CRR. This study has sought to establish molecular markers that will be useful for selecting for resistance to each of these important fungal diseases. Barley cultivars derived from the breeding line NDB112 have provided durable SB resistance in the North Dakota region of the USA for over 40 years. The robustness of this resistance had not been determined under Australian environmental conditions or with those B. sorokiniana pathotypes present within Australia. To elucidate the genetics of resistance, two seedling and two field trials were conducted on an ND11231-12/VB9524 (ND/VB) doubled haploid (DH) population (180 lines). A molecular map of the ND/VB population was curated in order to provide a firm basis for mapping of resistance loci. Composite interval mapping revealed that different gene combinations are effective at different stages of plant development. Seedling resistance was found to be conditioned by a major locus on the short arm of chromosome 7H and this region was validated in the related population ND11231-11/WI2875*17. A minor quantitative locus on chromosome 5HS was detected in one of the two seedling trials. However, this region requires further investigation to confirm its association to SB resistance in this population. Field resistance to SB in adult plants was found to be associated with two major quantitative trait loci (QTL)on chromosomes 7HS and 3HS; and a putative third minor QTL on chromosome 2HS. The 7H region is common between seedling and field resistance and is the most important locus for the expression of resistance at both stages of plant development. These findings largely concur with genetic studies of this trait in tworowed barley germplasm in North American environments. Common root rot is a difficult disease to phenotype for, and breeding programs will benefit from the identification of molecular markers linked to resistance. Data was provided from field trials of subsets of the population over four years. Using a novel approach combining the efficiency of bulked-segregant analysis with highthroughput Diversity Arrays Technology markers (BSA-DArT), CRR resistance was found to be conditioned by three putative QTL in an unmapped Delta/Lindwall population. QTL were identified on chromosomes 2HS, 4HS, and 7HS. To validate the trait-linkage associations between the DArT markers and the CRR QTL,microsatellite (SSR) markers known to map to the regions identified by BSA-DArT were used. The 2H and 4H regions were validated using marker regression of the SSR markers in most seedling trials, whereas the 7H QTL, which is proximal to the location of the SB resistance QTL in the ND/VB population, was detected in only one seedling trial. The QTL identified in this study offer potential to combat the foliar and root diseases causes by this fungal pathogen. The chromosomal location of QTL for SB and CRR resistance have been found to differ in the ND/VB and D/L populations,which suggests that resistance to each disease is independently inherited. Further research is required to confirm the hypothesis that it is possible to combine resistance to both diseases into a single genotype. Such allelic combinations would provide elite germplasm that would benefit barley breeding programs world-wide

Confirmation of the barley vacuolar pyrophosphatase HvHVP10 as a candidate gene for salinity tolerance

Salinity is one of the most significant environmental issues affecting agricultural production in Australia and around the world. One main salinity tolerance mechanism among plants is the exclusion of sodium ions from the aerial parts of the plants. Conventional breeding techniques and genetic engineering approaches have been employed in the effort to develop varieties with lower levels of shoot sodium accumulation under saline conditions. A gene identification approach in the salt laboratory at the Australian Centre for Plant Functional Genomics (ACPFG) identified a major quantitative trait locus (QTL) for sodium exclusion (HvNax3) in the barley mapping population Barque-73 (Hordeum vulgare; a high yielding South Australian cultivar) × CPI-71284-48-48, (a wild barley; Hordeum spontaneum). Syntenic mapping revealed a number of candidate genes underlying the HvNax3 QTL, the most promising of which encodes a vacuolar pyrophosphatase proton pump (V-PPase, HVP10 gene in barley) responsible for establishing an electrochemical gradient across the tonoplast that drives the secondary transport of ions such as sodium into the vacuole. The compartmentalisation of sodium in the vacuole reduces the toxic effect of high sodium concentration in the cytoplasm, whilst at the same time facilitating water uptake into the plant. Orthologues of this gene have been shown to confer salinity and drought tolerance in a variety of plant species. In order to confirm that V-PPase is the gene responsible for the HvNax3 phenotype, analysis of the accumulation of sodium ions and HvHVP10 gene expression in root and shoot tissue was conducted over 10 days of salinity stress. Results of this work suggested that the accumulation of sodium in the roots of lines carrying the CPI-71284-48 HvNax3 allele may be attributed to a peak in HvHVP10 expression at day 3 of salinity stress. This finding is further supported by analysis of pyrophosphatase activity within root tonoplast enriched vesicles, results of which suggest that pyrophosphatase activity was higher in the line with the CPI-71284-48 HvNax3 allele in response to salinity stress. Sequence analysis of the HvHVP10 CDS, gene and promoter region suggests that this difference in expression and enzyme activity may be due to the presence of a DREB transcription binding site just upstream of the HvHVP10 start codon in CPI-71824-48. Future analysis is required to validate this finding and warrants further investigation, possibly by employing the newly emerging CRISPR technology. A significant component of this research project was the development of HvHVP10 overexpression (OEX) lines. The salinity tolerance of these lines was characterised in the T1 and T2 generation using a supported hydroponics system and destructive analysis. Results from this study indicated that is some cases the constitutive OEX of HvHVP10 lead to increased biomass of transgenic plants under both salinity stress and control conditions. Several transgenic lines also displayed altered patterns of sodium accumulation in the root and shoot tissue under 150 mM and 200 mM NaCl. Further analyses of these transgenic lines at later generations is required to confirm this phenotype and warrants future investigation.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food & Wine, 201

Mapping spot blotch resistance genes in four barley populations

Bipolaris sorokiniana (teleomorph: Cochliobolus sativus) is the fungal pathogen responsible for spot blotch in barley (Hordeum vulgare L.) and occurs worldwide in warmer, humid growing conditions. Current Australian barley varieties are largely susceptible to this disease and attempts are being made to introduce sources of resistance from North America. In this study we have compared chromosomal locations of spot blotch resistance reactions in four North American two-rowed barley lines; the North Dakota lines ND11231-12 and ND11231-11 and the Canadian lines TR251 and WPG8412-9-2-1. Diversity Arrays Technology (DArT)-based PCR, expressed sequence tag (EST) and SSR markers have been mapped across four populations derived from crosses between susceptible parental lines and these four resistant parents to determine the location of resistance loci. Quantitative trait loci (QTL) conferring resistance to spot blotch in adult plants (APR) were detected on chromosomes 3HS and 7HS. In contrast, seedling resistance (SLR) was controlled solely by a locus on chromosome 7HS. The phenotypic variance explained by the APR QTL on 3HS was between 16 and 25% and the phenotypic variance explained by the 7HS APR QTL was between 8 and 42% across the four populations. The SLR QTL on 7HS explained between 52 to 64% of the phenotypic variance. An examination of the pedigrees of these resistance sources supports the common identity of resistance in these lines and indicates that only a limited number of major resistance loci are available in current two-rowed germplasm

An autoactive NB-LRR gene causes Rht13 dwarfism in wheat

Semidwarfing genes have greatly increased wheat yields globally, yet the widely used gibberellin (GA)-insensitive genes Rht-B1b and Rht-D1b have disadvantages for seedling emergence. Use of the GA-sensitive semidwarfing gene Rht13 avoids this pleiotropic effect. Here, we show that Rht13 encodes a nucleotide-binding site/leucine-rich repeat (NB-LRR) gene. A point mutation in the semidwarf Rht-B13b allele autoactivates the NB-LRR gene and causes a height reduction comparable with Rht-B1b and Rht-D1b in diverse genetic backgrounds. The autoactive Rht-B13b allele leads to transcriptional up-regulation of pathogenesis-related genes including class III peroxidases associated with cell wall remodeling. Rht13 represents a new class of reduced height (Rht) gene, unlike other Rht genes, which encode components of the GA signaling or metabolic pathways. This discovery opens avenues to use autoactive NB-LRR genes as semidwarfing genes in a range of crop species, and to apply Rht13 in wheat breeding programs using a perfect genetic marker

Smoking Cessation Messages for Pregnant Aboriginal and Torres Strait Islander Women: A Rapid Review of Peer-Reviewed Literature and Assessment of Research Translation of Media Content

This review summarized literature about knowledge, attitudes, and beliefs of Aboriginal and Torres Strait Islander women from Australia who smoke during pregnancy, then examined the extent that existing health promotion materials and media messages aligned with evidence on smoking cessation for pregnant Aboriginal and Torres Strait Islander women. Knowledge, attitudes, and beliefs of pregnant Aboriginal women who smoke tobacco were identified in the literature. Health promotion campaigns were retrieved from a grey literature search with keywords and social and professional networks. Key themes from peer-reviewed papers were compared against the content of health promotion campaigns using the Aboriginal Social and Emotional Wellbeing Model, the Behavior Change Wheel and thematic analysis. Eleven empirical studies and 17 campaigns were included. Empirical studies highlighted women sought holistic care that incorporated nicotine replacement therapy, engaged with their family and community and the potential for education about smoking cessation to empower a woman. Health promotion campaigns had a strong focus on ‘engagement with family and community’, ‘knowledge of risks of smoking,’ ‘giving up vs cutting down’ and ‘culture in language and arts’. There were similarities and variances in the key themes in the research evidence and promotion materials. Topics highly aligned included risks from smoking and quitting related issues

HVP10 encoding V-PPase is a prime candidate for the barley HvNax3 sodium exclusion gene: evidence from fine mapping and expression analysis

In cereals, a common salinity tolerance mechanism is to limit accumulation of Na(+) in the shoot. In a cross between the barley variety Barque-73 (Hordeum vulgare ssp. vulgare) and the accession CPI-71284 of wild barley (H. vulgare ssp. spontaneum), the HvNax3 locus on chromosome 7H was found to determine a ~10-25 % difference in leaf Na(+) accumulation in seedlings grown in saline hydroponics, with the beneficial exclusion trait originating from the wild parent. The Na(+) exclusion allele was also associated with a 13-21 % increase in shoot fresh weight. The HvNax3 locus was delimited to a 0.4 cM genetic interval, where it cosegregated with the HVP10 gene for vacuolar H(+)-pyrophosphatase (V-PPase). Sequencing revealed that the mapping parents encoded identical HVP10 proteins, but salinity-induced mRNA expression of HVP10 was higher in CPI-71284 than in Barque-73, in both roots and shoots. By contrast, the expression of several other genes predicted by comparative mapping to be located in the HvNax3 interval was similar in the two parent lines. Previous work demonstrated roles for V-PPase in ion transport and salinity tolerance. We therefore considered transcription levels of HVP10 to be a possible basis for variation in shoot Na(+) accumulation and biomass production controlled by the HvNax3 locus under saline conditions. Potential mechanisms linking HVP10 expression patterns to the observed phenotypes are discussed.Yuri Shavrukov, Jessica Bovill, Irfan Afzal, Julie E. Hayes, Stuart J. Roy, Mark Tester, Nicholas C. Collin

Prophylaxis of postoperative endophthalmitis following cataract surgery: Results of the ESCRS multicenter study and identification of risk factors

Purpose: To identify risk factors and describe the effects of antibiotic prophylaxis on the incidence of postoperative endophthalmitis after cataract surgery based on analysis of the findings of the European Society of Cataract & Refractive Surgeons (ESCRS) multicenter study. Setting: Twenty-four ophthalmology units in Austria, Belgium, Germany, Italy, Poland, Portugal, Spain, Turkey, and the United Kingdom. Methods: A prospective randomized partially masked multicenter cataract surgery study recruited 16 603 patients. The study was based on a 2 × 2 factorial design, with intracameral cefuroxime and topical perioperative levofloxacin factors resulting in 4 treatment groups. The comparison of case and non-case data was performed using multivariable logistic regression analyses. Odds ratios (ORs) associated with treatment effects and other risk factors were estimated. Results: Twenty-nine patients presented with endophthalmitis, of whom 20 were classified as having proven infective endophthalmitis. The absence of an intracameral cefuroxime prophylactic regimen at 1 mg in 0.1 mL normal saline was associated with a 4.92-fold increase (95% confidence interval [CI], 1.87-12.9) in the risk for total postoperative endophthalmitis. In addition, the use of clear corneal incisions (CCIs) compared to scleral tunnels was associated with a 5.88-fold increase (95% CI, 1.34-25.9) in risk and the use of silicone intraocular lens (IOL) optic material compared to acrylic with a 3.13-fold increase (95% CI, 1.47-6.67). The presence of surgical complications increased the risk for total endophthalmitis 4.95-fold (95% CI, 1.68-14.6), and more experienced surgeons were more likely to be associated with endophthalmitis cases. When considering only proven infective endophthalmitis cases, the absence of cefuroxime and the use of silicone IOL optic material were significantly associated with an increased risk, and there was evidence that men were more predisposed to infection (OR, 2.70; 95% CI, 1.07-6.8). Conclusions: Use of intracameral cefuroxime at the end of surgery reduced the occurrence of postoperative endophthalmitis. Additional risk factors associated with endophthalmitis after cataract surgery included CCIs and the use of silicone IOLs. © 2007 ASCRS and ESCRS