Race-specific aspects of polygenic resistance of barley to leaf rust,Puccinia hordei

Partial resistance of barley to leaf rust,Puccinia hordei, is characterized by a reduced rate of epidemic development in spite of a susceptible infection type. Barley cultivars vary greatly for partial resistance and its components. In a test for interaction between host cultivars and pathogen isolates most variation was of a horizontal nature. However, in the combination between Julia and the rust isolate 18, a differential interaction (vertical effect) occured; Julia had lost a small part of its partial resistance. The same interaction was found for latent period (LP), the most important component of partial resistance. Julia showed a shortened LP for isolate 18. Genetic analyses revealed, that Julia carries a polygene for longer LP not present in the other cultivars. The effect of this polygene appears to be broken by isolate 18 indicative for a gene-for-isolate relation, and even for a gene-forgene relation.Samenvatting Partiële resistantie van gerst voor dwergroest,Puccinia hordei, is gekenmerkt door een vertraagde epidemie-opbouw ondanks een vatbaar infectietype. Gerstrassen variëren sterk in partiële resistentie en haar componenten. In een toets ter bestudering van de interactie tussen waardplant en pathogeenisolaat bleek de meeste variatie horizontaal van aard te zijn. In de combinatie van Julia met isolaat 18 werd echter een differentiële interactie waargenomen; Julia had een klein deel van zijn partiële resistentie verloren. Dezelfde interactie werd waargenomen voor de belangrijkste component van partiële resistentie, de latentieperiode (LP); Julia had een iets verkorte LP voor isolaat 18. Genetische analyses toonden aan, dat Julia een polygen voor langere LP bevat; dit gen is niet aanwezig in de andere bestudeerde rassen. Er wordt verondersteld dat het effect van dit polygen door isolaat 18 is doorbroken. Dit wijst op een gen-om-isolaat en zelfs op een gen-om-gen-relatie.     

Analysis of variation in agronomic characters and partial resistance to barley leaf rust (Puccinia hordei) pathotype ETPh7611 of barley landrace collections

European Journal of Plant Pathology - The main germplasm resource bases used for genetic diversity in disease resistance include wild ancestral species, landraces and commercial varieties. In this...     

The effect of leaf rust (Puccinia hordei) on yield response in barley (Hordeum vulgare L.) crops with different yield potentials

The effect of leaf rust was investigated on field-grown crops, in two consecutive seasons, each at a single location, using a non-replicated design. The experiments involved three crops and 10 distinct epidemics in the 1987/8 season, and four crops with seven epidemics in the 1988/9 season. The epidemics were concurrent in each season in subplots within each crop, and the yield range was from 2.2–9.0 t ha⁻¹ in nil-diseased plots. Variation in the experiments, assessed as the percentage coefficient of variation, was in the same range as similar, but replicated, experiments with fewer treatment combinations. Early sowing and high agronomic inputs were associated with greater leaf areas, green area durations and yields than in comparable crops sown later or with lower inputs. Disease intensity was described both by per cent disease severity and by the effect on green area. Disease reduced yield mostly via reduced number of fertile ears (mean 31% for all crops) and grain weight (21% mean reduction). Reductions in these components were greater in the 1987/8 season than in the 1988/9 season, but there was no consistent effect associated with yield potential. The number of grains per ear was affected much less (2.5% mean for all crops) than the other components. There was little evidence for compensation between yield components.     

The effect of powdery mildew (Erysiphe graminis f. sp. hordei) and leaf rust (Puccinia hordei) on spring barley in New Zealand. II. Apical development and yield potential

Reduced yields caused by powdery mildew and leaf rust in two seasons were associated with reduced plant growth. Combinations of early, late and full epidemics in one season, and 12 epidemic combinations in the second, were designed to identify crop sensitivity to disease by comparing growth and development with healthy plants. Early epidemics reduced ear number by increasing tiller death, and reduced grain number by effects on spikelet, floret or grain abortion, depending on the type of epidemic. Epidemics later in crop growth increased floret and grain abortion and also reduced grain weight.
There was no compensation by later-determined components for reduced growth and delayed development at earlier growth stages. Plants infected at early growth stages were more sensitive to late infections, seen as effects on the later-determined components, than plants which were healthy initially. Interactions occurred between epidemics at different times and are likely to occur between diseases and other constraints.     

Virulence spectrum of Puccinia hordei in barley production systems in Ethiopia

Barley leaf rust caused by Puccinia hordei is an important disease of barley in Ethiopia. In the 2003 and 2004 cropping seasons, surveys of P. hordei were conducted on fields in the main rainy, residual moisture and short rainy season-barley production systems. A total of 381 isolates were analysed on 12 barley differential hosts carrying different Rph resistance genes ( Rph1 – Rph12 ). Based on infection phenotypes on leaf rust ( Rph ) resistance genes, seven pathotypes were identified, namely ETPh7611, ETPh7631, ETPh6611, ETPh7651, ETPh7671, ETPh7653 and ETPh7633, with frequencies of 63·0, 21·5, 6·8, 2·9, 2·6, 2·1 and 1·2%, respectively. ETPh7611 and ETPh7631 were the most common pathotypes found in all the surveyed areas of the three production systems. ETPh7653 was found in the small rainy season production system only. ETPh7671, ETPh7653 and ETPh7633 were the most virulent, but the least frequent, pathotypes. All isolates were virulent on resistance genes Rph1 , Rph4 , Rph8 , Rph9 , Rph11 and Rph12 . Virulence against Rph3 and Rph7 was absent. Genes Rph2 , Rph6+2 , Rph5 and Rph10 were effective against 96·3, 88·9, 65 and 2·4% of the rust isolates tested, respectively.     

The effect of powdery mildew (Erysiphe graminis f. sp. hordei) and leaf rust (Puccinia hordei) on spring barley in New Zealand. I. Epidemic development, green leaf area and yield

Powdery mildew and leaf rust caused large yield losses in spring barley grown near Christchurch, New-Zealand, in two seasons. Disease present during early growth stages was as damaging to yield as disease late in the season. Moderate leaf rust severities after anthesis were most damaging when combined with earlier mildew epidemics. Later growth did not compensate for reduced yield potential induced by early infection. This was attributed, at least in part, to an effect on leaf size, and therefore on green leaf area, at later growth stages. There was a closer relationship, by regression analysis, of yield to green leaf area than to disease severity in three cultivars.
The three cultivars. which differed in yield potential and disease resistance, were not equally sensitive to disease. It is proposed that high yielding cultivars may be the most sensitive to yield constraint by disease.     

Resistance of some barley cultivars to leaf rust,Puccinia hordei; polygenic,partial resistance hidden by monogenic hypersensitivity

Three cultivars, all carrying the Pa7 gene for low infection type were crossed with ‘L94’, a cultivar assumed to carry no genes for partial resistance. The latent period (LP), the most important component determining partial resistance, was measured on 111 F₂ plants not carrying the Pa7 gene and on four cultivars representing the known range in LP. Of 20 F₃ lines the LP was evaluated, too. The F₂ showed a continuous segregation for LP from nearly as short as ‘L94’ to as long as ‘Vada’. This was substantiated by the F₃ data. The cultivars possessing the Pa7 gene are assumed to carry a series of minor genes, covered by Pa7, which govern a LP at least as long as that of ‘Vada’, a cultivar with a very high level of partial resistance and a long LP.     

Resistance in Australian barley (Hordeum vulgare) germplasm to the exotic pathogen Puccinia striiformis f. sp. hordei,causal agent of stripe rust

Eighty‐eight Australian and 10 international barley cultivars were assessed for resistance to the barley stripe (yellow) rust pathogen, Puccinia striiformis f. sp. hordei (Psh). All cultivars were tested for seedling resistance to two UK‐derived isolates of Psh (11.01 and 83.39) that were shown to differ in virulence based on responses on 16 differential barley genotypes. The 98 barley cultivars differed substantially in stripe rust response; 45% were susceptible to Psh 11.01, 53% to Psh 83.39 and 44% to both isolates. The observed diverse infection types (ITs) suggest the presence of both known and uncharacterized resistance. However, further multipathotype tests are required for accurate gene postulation. The Yerong × Franklin (Y×F) doubled haploid (DH) population was phenotypically assessed as seedlings using both Psh isolates. Yerong and Franklin were immune and highly resistant, respectively, to both isolates used in this study. Marker‐trait and QTL mapping identified a major effect on the long arm of chromosome 7H contributed by Franklin in response to all isolates. The resistance of Yerong was mapped to 113·96 and 169·38 cM on chromosome 5HL in response to Psh 11.01 and 83.39, respectively. The Psh resistance sources identified in this study can be used for further genetic analysis and introgression for varietal improvement.     

The development of the leaf rust,Puccinia hordei,population during winter,spring and early summer in 11 winter barley cultivars

The overwintering and the epidemic development in spring of leaf rust was studied in 11 winter barley cultivars at two different sites near Wageningen in 1976/1977. The amount of leaf rust decreased through the winter at both sites. Cultivars differed considerably in the amount of leaf rust in late winter. Both the moment and the rate of increase of leaf rust after the winter varied with cultivars. The ultimate amount of leaf rust in a cultivar was therefore determined by three factors: The amount of overwintering leaf rust, the onset of leaf rust increase and the rate of increase. The latter was determined by the partial resistance of the cultivar. Why the epidemics did not start at the same moment is yet unknown. The differential overwintering could be explained from the amounts of leaf rust and powdery mildew at the start of the winter, the effect of powdery mildew being a negative one. The correlation coefficient between the values observed in March and those predicted from the December leaf rust and powdery mildew readings was 0.93. In a second experiment carried out in 1979/1980 with six winter barley cultivars chosen from the first experiment the powdery mildew was succesfully excluded by treatment with fungicides. There was no decrease in the leaf rust over the winter nor a differential cultivar effect on overwintering.     

International testing of incomplete resistance against brown rust (Puccinia recondita) in IPHR wheat lines

Promising wheat lines from FAO's International Program for Horizontal Resistance (IPHR) in Brazil and Zambia were tested in the Netherlands against brown rust (Puccinia recondita. f.sp.tritici). Race nursery tests were performed on isolated field plots using five monopustular isolates from the Netherlands representing at least four races. Mature plants of several lines showed high incomplete resistance. For most lines, the reactions to the different races showed a high uniformity. Apparently, lines selected according to the IPHR principles can perform well when exposed to brown rust isolates to which they have not been exposed during selection.Samenvatting Veelbelovende tarwelijnen uit het Internationale Programma voor Horizontale Resistentie (IPHR) van de FAO in Brazilië en Zambia werden in Nederland getoetst tegen bruine roest (Puccinia recondita f.sp.tritici). Hierbij werd gebruik gemaakt van de fysiovelden-techniek. Geïsoleerde fysiovelden werden geïnoculeerd met vijf Nederlandse isolaten, ieder afkomstig van een sporenhoopje. Deze vijf isolaten vertegenwoordigden ten minste vier fysio's. Bij verscheidene lijnen vertoonden de volwassen planten een hoge mate van onvolledige resistentie. De meeste lijnen vertoonden in hun reactie op de verschillende fysio's een hoge mate van uniformiteit. Kennelijk kunnen lijnen, geselecteerd volgens de beginselen van het IPHR goede resultaten geven wanneer zij getoetst worden met roest-isolaten, waaraan zij tijdens het selectieproces nooit zijn blootgesteld.     

Appresoorium formation of Puccinia hordei on partially resistant barley and two non-host species

One of the components of partial resistance of barley to leaf rust,Puccinia hordei, is a reduced infectibility. It was investigated whether this low infectibility may rest on a hampered appressorium formation of the leaf rust fungus. The appressorium formation on the primary leaves of 11 barley genotypes with an intermediate-to-low infectibility was compared with that on the highly infectible L94. The number of stomata per cm² leaf area occupied by appressoria ofP. hordei was determined per genotype by means of fluorescence microscopy. No cosistent differences could be detected, indicating that the mechanisms causing a low infectibility of partially resistant barley seedlings act at a phase later than the formation of the appressoria. On the non-host wheat not fewer appressoria were formed than on L94, but no appressoria were found on a lettuce genotype. The latter probably lacks the stimuli that enable the fungus to find stomata.Samenvatting Eén van de componenten van partiële resistentie van gerst tegen dwergroest,Puccinia hordei, is een verminderde infectiedichtheid. Het mechanisme, dat hieraan ten grondslag ligt, is onbekend. Een experiment werd uitgevoerd om na te gaan of bij partieel resistente rassen een verminderde appressoriumvorming optreedt. Na inoculatie in een inoculatietoren en een zorgvuldig uitgevoerde incubatie werd het aantal huidmondjes per cm² bladoppervlak bepaald dat bezet was door appressoria vanP. hordei. De elf weinig vatbare gerstlijnen uit deze studie bleken niet reproduceerbaar te verschillen van de zeer vatbare gerstlijn L94 in de mate van appressoriumbezetting. Dit wijst erop dat infectiedichtheidsverschillen t.g.v. partiële resistentie veroorzaakt worden door mechanismen die werken na de appressoriumvorming. In een tweede experiment werd aangetoond dat zelfs op de niet-waardsoort tarwe, waaropP. hordei geen symptomen veroorzaakt, niet minder appressoria worden gevormd dan op L94. Op een sla-genotype trad echter geen appressoriumvorming op. Op deze laatste niet-waardsoort ontbreken waarschijnlijk de stimuli die de schimmel in staat stellen huidmondjes te vinden.     

Roles of peroxidases and NADPH oxidases in the oxidative response of wheat (Triticum aestivum) to brown rust (Puccinia triticina) infection

The goal of this work was to establish which enzymes – peroxidases or NADPH oxidases – play the most important role in the resistance‐related oxidative burst response of wheat to infection by brown rust (Puccinia triticina). The expression of four peroxidases and two NADPH oxidases was analysed in the susceptible wheat cv. Thatcher and isogenic lines with different Lr resistance genes after pathogen inoculation. Of the peroxidases, TaPrx118 and TaPrx112 were induced several times more strongly than TaPrx103 and TaPrx107. The induction of peroxidases was more pronounced than that of NADPH oxidases. The patterns of peroxidase expression clearly differentiated moderately resistant from highly resistant lines and corresponded to oxidative response profiles. The possible involvement of peroxidases or NADPH oxidases was verified with enzyme‐specific inhibitors. The oxidative burst in the susceptible cv. Thatcher and in the lines TcLr24, TcLr25, TcLr9 was peroxidase‐dependent, while the response in line TcLr26 was NADPH‐oxidase‐dependent. It is postulated that class III peroxidases play a leading role in the formation of reactive oxygen species molecules during the response of wheat to pathogen infection. The results suggest a high level of redundancy of some peroxidase genes induced in biotic stress. The role of both enzyme systems in wheat response/resistance to brown rust is discussed in relation to the oxidative response, the efficiency of resistance, and the presence and origin of particular Lr resistance genes.     

Identification of a quantitative trait locus for high-temperature adult-plant resistance against Puccinia striiformis f. sp. hordei in 'Bancroft' barley

Sustainable control of plant diseases can be achieved by developing cultivars with durable resistance. 'Bancroft' barley has durable high-temperature, adult-plant (HTAP) resistance to stripe rust caused by Puccinia striiformis f. sp. hordei. The objectives of this study were to determine the inheritance of the HTAP resistance in Bancroft, develop molecular markers for the HTAP resistance using the resistance gene analog polymorphism (RGAP) technique, map the HTAP resistance quantitative trait locus or loci (QTL) on barley chromosomes, and determine the usefulness of the RGAP markers in other barley cultivars for marker-assisted selection. The parents and F(4) recombinant inbred lines (RIL) and the parents and F(5) RIL were evaluated in 2004 and 2005 in one and three field sites, respectively, in Washington State. Infection type (IT) and disease severity (DS) were recorded three times at each location during each growing season. Area under the disease progress curve (AUDPC) was calculated for each parent and RIL based on the DS data. Genetic analyses of IT data of the parents, F(1), and F(2) tested in the adult-plant stage under controlled high-temperature cycle in the greenhouse and the parents, F(4), and F(5) RIL in the field indicated that one dominant gene controlled the HTAP resistance in Bancroft. Using 119 F(5:6) RIL and IT data, a linkage map on chromosome arm 3HL was constructed with eight RGAP markers and three simple sequence repeat (SSR) markers. Using the QTL analysis, a QTL for HTAP resistance was mapped with the DS and AUDPC data on the same chromosome location as with the IT data. The QTL explained >70% of the total phenotypic variation for the DS and AUDPC. The heritability of the HTAP resistance based on the AUDPC data was 76%. The two markers most close to the QTL peak detected polymorphisms in 84 and 88% of 25 barley genotypes that do not have the Bancroft HTAP resistance when used individually, and detected polymorphism in 100% of the genotypes when used in combination, indicating that the markers could be used in incorporating the HTAP resistance into these barley genotypes to improve the level and durability of resistance to stripe rust.     

Genes for race-specific resistance to yellow rust (Puccinia striiformis) in Indian wheat cultivars

Seedlings of Indian wheat cultivars (Kalyansona, Sonalika, WL711 and eight others released commercially) were tested with 13 British and four alien races of Puccinia striiformis. The data indicated the probable presence of the resistance gene Yr2 in the three cultivars named above and in six of the others. Reactions of the remaining two cultivars, PWB12 and WL2265, were consistent with the presence of the gene 177. The presence of Yr2 in Kalyansona, Sonalika and WL711 was supported by evidence from crosses between them and with Heines VII, which is known to carry Yr2. In crosses of Sonalika with a susceptible cultivar, Kharchia Local and also with WL711, tests of F1, F2 and F3 generations indicated that, in addition to Yr2 , Sonalika possesses at least two other genes. Both these genes were difficult to detect but the F3 data supported the hypothesis that there is a single partially recessive gene giving resistance to alien race 6E16 and a different, possibly complementary, gene system effective against another alien race, 39E134. The presence of resistance in addition to Yr2 was also detected in WL711 and HD2329.     

河南省2004年夏玉米锈病发生原因及防治对策

根据2004年河南省玉米锈病暴发实际情况,重点从品种、菌源和气候3个方面分析了暴发的原因,并提出了相应的防治对策及措施.     

菊花白锈病在吉林市严重发生

菊花白锈病是菊花上的重要病害 ,1895年日本首先发现 ,196 4年之后 ,欧洲许多国家相继报道发生。美国等一些国家为防止该病传入 ,将其列入检疫对象。 1979年与 1994年我国检疫部门从日本引进的菊花中发现该病。 2 0 0 0年吉林市花圃中该病严重发生 ,调查发现京白、四季黄两个菊