Inheritance of resistance to Pyrenophora teres f. teres in spring barley

The inheritance of seedling resistance to a Swedish isolate of Pyrenophora teres f. teres was investigated in four resistance sources of spring barley. Accessions CI 2330, CI 5791, CI 5822 and CI 9779 were used as resistance sources, and the cultivar ‘Alexis’ was used as a susceptible parent in different crosses. From the disease reaction in the F₁, F₂ and F₃ generations it was concluded that the resistance was governed by the same two complementary genes in CI 5791, CI 822 and CI 9776. One of these genes was present in CI 2330. The first three cultivars were highly resistant to the isolate used in this investigation. These results, when combined with earlier studies, suggest that CI 5791, CI 5822 and CI 9776 may be of great value as sources of resistance to barley net blotch. Spearman's rank correlation between the disease reaction of F₂ plants and their F₃ progeny was highly significant (r = 0.75; P ≥ 0.001) It is suggested that selection in the F₂ generation is effective. In a backcross breeding scheme, single plant reactions in F₁ or F₂ need to be confirmed in later generations.     

Yield of doubled haploid lines of Nordic spring barley infected with net blotch, Pyrenophora teres

Five Nordic spring barley lines (‘Rolfi’, ‘Arve’, ‘Botnia’, ‘Pohto’ and WW7977) and doubled haploid (DH) populations from a half diallel of crosses between them, were sown in the field in Finland over 2 years and were artificially infected with Pyrenophora teres, the causal agent of net blotch. The purpose of the experiments was to determine the extent of yield loss under net blotch infection in a range of parent barleys and DH populations differing in symptom expression. Analysis of foliar damage symptoms, yield and aerial biomass data indicated that, in both years, there were statistically significant differences among parents and crosses, but the relationships between symptom expression and yield maintenance and between symptom expression and aerial biomass maintenance were stronger in 1997, when yields were higher and net blotch was less severe.     

Virulence studies of Swedish net blotch isolates (Drechslera teres) and identification of resistant barley lines

Six Swedish and one Canadian single spore isolate of Drechslera teres f. teres were used to screen 109 barley lines for disease resistance and to select a differential set of barley lines for use in assessing pathogen virulence. A large variation for net blotch resistance was found among the 109 barley lines which were classified into four groups, those showing: 1) only resistant reactions; 2) differential reactions; 3) only intermediate reactions and 4) only susceptible reactions. The European commercial varieties included, showed susceptibility to all Swedish isolates, but a few were resistant to the Canadian isolate. The 18- member differential set separated 25 Swedish and two Canadian isolates of D. teres into 14 pathotypes, three of which made up 59% of the isolates. Only one barley differential (CI 9776) was resistant to all net form isolates. Host selection on the pathogen seems to be present as all six isolates obtained from cv. Golf belonged to the same pathotype and 4 of 5 isolates from cv. Karin shared the same virulence pattern. The net form of net blotch (D. teres f. teres) predominated in the sampled regions and only one of 26 Swedish isolates was of the spot form (D. teres f. maculata). This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of Partial Resistance to Net Blotch in Barley

Reciprocal crosses were made between 9 different barley genotypes with high genetic variability for net blotch resistance. Parents and 72 F₁ plants were used to determine the inheritance of partial resistance to net blotch. Four experiments, one in a growth chamber on seedlings and 3 others in the field on adult plants, were undertaken using a randomised complete block design. An isolate of net blotch from local cultivars was used for inoculation. Non-inoculated plants of one of the field experiments were used for the detached leaf test in petri dishes. Results show that the cultivars ‘Banteng’, and ‘Arrivate’, the Ethiopian line CI 5791, and the Syrian line 79 SIO-10, had a high partial resistance in all experiments. Diallel analysis showed high significant general and specific combining ability when maternal and reciprocal effects were not significant. As the resistance genotypes have a high additive genetic effect, they could be successfully used for breeding purposes.     

Radiation interception and radiation use efficiency of near-isogenic wheat lines with different height

Resistance to Pyrenophora teres Drechs. f. teres Smedeg., the net blotch pathogen, was studied in six 6-row Nordic spring barleys (Hordeum vulgare L.) in the field and in the greenhouse. The barley genotypes were: Arve, Agneta, Artturi, H6221, Pohto and WW7977. Disease progress was monitored in the field (1994 and 1995) in small artificially infected plots, sown at commercial seeding rates, and in infected hill plots (1994). Areas under the disease progress curves (AUDPC) and apparent infection rates (r) were calculated for the uppermost 3 or 4 leaves. Terminal severities (TS) were also recorded. Infection response of seedlings to a range of P. teres isolates was assessed in the greenhouse using a standard scale. In small plots in the field, Arve and Agneta were very susceptible to P. teres infection, as indicated by large values for AUDPC and TS. H6221 and WW7977 were highly resistant, while Artturi and Pohto were moderately resistant. In hill plots the situation was similar, except that Artturi and Pohto appeared less resistant than in the small plots. The relatively greater resistance of H6221 and WW7977 was reflected in seedling infection responses. According to the results of these experiments, H6221 and WW7977 possess adequate levels of quantitative resistance to P. teres to make them useful parents in future crossing programs aimed at improving net blotch resistance in Finnish spring barleys. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mapping seedling resistance to net form of net blotch (Pyrenophora teres f. teres) in barley using detached leaf assay

To develop molecular markers against Pyrenophora teres f. teres in barley, a detached leaf assay was conducted on two DH populations with a set of 11 single conidial lines (SCLs). Out of these, three showed different reactions in the DH population ‘Uschi × HHOR3073’ and two in ‘(P x V) × HHOR9484’. For SCL ‘QLB’, a 1r : 1s (χ² = 2.78) segregation was observed in the population ‘Uschi × HHOR3073’. In contrast to this, a continuous variation was observed for the SCL ‘WvB’ and ‘d8_4’ in the DH population ‘Uschi × HHOR3073’ and for ‘AR’ and ‘net1840’ in ‘(P × V) × HHOR9484’. With respect to resistance to the SCL ‘QLB’, a single major gene was located on chromosome 7H, and for resistance against SCL ‘WvB’, two QTLs were detected on chromosome 3H and 7H, and against SCL ‘d8_4’, two loci were mapped on chromosome 3HS in ‘Uschi × HHOR3073’. In the DH population ‘(P x V) × HHOR9484’, one locus conferring resistance to the SCL ‘AR’ was located on chromosome 3H. For resistance to SCL ‘net1840’, two QTLs were mapped on chromosome 4H and 5H.     

Stable resistance in barley to Pyrenophora teres f. teres isolates from the Nordic-Baltic region after increase on standard host genotypes

Results from tests of a mixture of Finnish net blotch, Pyrenophora teres Drechs. f. teres Smedeg., isolates on a differential series of barley seedlings, comprising 17genotypes, indicated that patterns of infection response (IR)and percentage leaf area damaged (PLAD) were unaffected by differences in seedling size. Variation of the concentration of inoculum between 1,250 conidia ml^-1 and 20,000 conidia ml^-1 produced similar patterns of IR and PLAD on the differential series. IR and PLAD scored on the second seedling leaf differentiated resistance to P. teres f. teresamong the genotypes better than on the first seedling leaf. Ina second experiment, 120 single-spore P. teres f. teres isolates from Finland, Sweden, Norway, Latvia, Estonia and Ireland were used in tests conducted in the greenhouse to differentiate them in terms of virulence reaction on seedlings of six differential barley genotypes. Each isolate was tested directly following isolation from the leaf material and after having passaged each through barley cvs. Arve or Pohto, to produce 360 isolates in total. Virulence of the isolates differed significantly on the members of the differential series, but differences associated with country of origin and passaging, and interactions, were small. It is concluded that little variation between virulence of P. teres f. teres isolates is evident over a large geographic area, incorporating Nordic and Baltic countries, and Ireland. Barley genotype response to P. teres f. teres appeared to be of more significance than relative virulence of the pathogen isolates. This could simplify breeding barley for improved resistance to this phytopathogen. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diallel analysis of net blotch resistance in doubled haploid lines of Nordic spring barleys

A half-diallel was made between five six-rowed Nordic spring barleys to study the genetics of resistance to net blotch. Twenty-five doubled-haploid (DH) lines from each cross and the parents were sown in hill plots in Finland in 1997 and 1998. The plots were artificially inoculated with Pyrenophora teres Drechs. f. teres Smedeg. and assessed for resistance to net blotch. There were statistically significant differences in resistance of the five parents to net blotch. General combining ability (GCA) of the parents and specific combining ability (SCA) effects in the progeny were statistically significant in both years, but GCA effects predominated. Evidence for additive epistasis was minimal. Progeny of a particular cross were less resistant to net blotch than the better parent. The most resistant progeny were derived from the cross between the two most resistant parents, Pohto and WW7977, and resistance was governed by at least eleven effective factors. Narrow sense heritability estimates for resistance to net blotch were high during both years (0.84–0.99). It appears that net blotch resistance of progeny from crosses can be largely predicted from reactions of the parents. Quantitative resistance to net blotch can be further advanced by identification and incorporation of superior parents, from a screening such as reported here, into a recurrent selection breeding programme. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic Variability for Grain Yield and Protein Content in Barley and Its Modification by Net Blotch

Protein content, yield and 1000-grain weight of healthy and net blotch-diseased plants were studied in a diallel cross programme concerning nine different varieties of barley (Hordeum vulgare L.). F₁ hybrids and their parents were grown in the field in two randomized block design experiments each with three replications (three inoculated and three non-inoculated plots). General and specific combining abilities were determined for yield, protein percentage, 1000 grain weight, protein yield, and non-protein yield. A high genetic variability for the traits studied was observed. Non-protein yield and 1000-grain weight decreased significantly in inoculated plants where protein yield was not affected. Significant general and specific combining abilities were observed for all traits. Values for general and specific combining abilities were, in some cases, significantly modified by net blotch of barley. This indicates that attention must be paid to the danger of drawing conclusions in quantitative genetics studies dealing with both diseased and healthy plants.     

Reaction of European spring barley varieties to a population of the net blotch fungus

About 320 European spring barley varieties and about 40 spring barley lines were tested in the field for reaction to a local population of the spot form of the net blotch fungus Pyrenophora teres forma maculata with the imperfect stage Drechslera teres. The European barley varieties showed a wide range of disease reactions, from nearly resistant to very susceptible. At least three groups of genetically related barley varieties could be distinguished: (0)‘Agneta’ and ‘Clermont’, (2)‘Nordal’ and ‘Arve’, and (3)‘Tellus’,‘Pamina’, ‘Albert’ and ‘Birka’. The parentages of these three groups of barley are mutually distantly related and may thus constitute three different sources of resistance to the pathogen population used. The range of disease reaction is similar in varieties from different European countries but it differs among different breeding stations. The relatively high level of resistance is fairly uniformly distributed in contemporary barley varieties all over most of Western Europe. Over time, from about 1830‐1982, the average level of resistance varied around 4.0 (scale value) (from 2.8 to 4.8). However, since about 1940 the variation in disease reaction has become much wider (from 108 to 6.9) for unknown reason(s).     

Gene for Resistance to Barley Mild Mosaic Virus in German Winter Barley Located on Chromosome 3L

In order to identify the chromosome arm carrying a gene for resistance to barley mild mosaic virus (BaMMV) in German winter barley cultivars, a line trisomic for the long arm of chromosome 3 (telo-trisomic 3L) was crossed to the resistant cvs. ‘Sonate’ and ‘Ogra’. Results of tests for BaMMV reaction in the F2 indicate that the gene for resistance in German cultivars is located on the long arm of chromosome 3.     

Variation in Ethiopian barley landrace populations for resistance to barley leaf scald and netblotch

One-hundred and eighty landrace populations and six-hundred single-head plants selected from 60 promising populations were evaluated for resistance to scald and netblotch at three locations in Ethiopia. Each accession was tested with and without the application of 50% of the recommended rate of fertilizer at planting. Plants were rated for disease attack two to four times during the season. Both diseases were enhanced by the application of fertilizer and were more severe at the testing sites of Holetta and Bekoji than at Sheno. The difference in disease resistance among and within populations was considerable. Moreover, populations from Arsi and Bale tend to be more susceptible to scald but more resistant to netblotch than populations from other regions. Populations collected from higher altitudes were more resistant to scald, but susceptible to netblotch, than were populations from lower altitudes. The paper illustrates approaches to the identification of valuable genotypes from landrace populations that can be incorporated into a breeding programme for the development of improved varieties with resistance to the principal diseases of barley in Ethiopia.     

Inheritance of Resistance to Mycosphaerella graminicola in Hexaploid Wheat

Septoria tritici blotch constitutes a major disease problem of wheat world-wide. To efficiently breed wheat for resistance to this disease, an understanding is required of the inheritance of resistance. Our objective was to study the quantitative inheritance of resistance under field conditions. A nine-parent diallel and a generation mean experiments were conducted at Toluca, México in 1986 and 1987, respectively, to investigate gene effects. General combining ability effects accounted for most of the variation although specific combining ability effects were detected in some crosses. Ias20*5/H567.71, Thornbird, and RPB709.71/Coc contributed the most to reduced disease severity. Reciprocal effects were detected in two of 36 crosses, where RPB709.71/Coc contributed additional reduced disease severity when used as female. The analysis of generation means confirmed results obtained from the diallel. Additive effects were also most important. Dominance effects and epistasis, mostly of the additive × additive type, were found in some crosses. Hence, substantial genetic progress for resistance can be expected among progeny from crosses with resistant parents. However, selection would be most effective if delayed to later generations because of dominance, and choice of the specific female parent may produce a higher level of resistance.     

Inheritance of tolerance to zinc deficiency in barley

Barley (Hordeum vulgare L.) is often grown on alkaline zinc (Zn)‐deficient soils where reductions in yield and grain quality are frequently reported. Currently, the use of Zn‐based fertilizer along with Zn‐deficiency‐tolerant genotypes is considered the most thorough approach for cropping the Zn‐deficient soils; however, developing or breeding genotypes with higher Zn efficiency requires a good understanding of the inheritance of tolerance to Zn deficiency. This study was conducted to determine genetic control of this trait in barley. Two parental cultivars ('Skiff, moderately tolerant; and ‘Forrest’, sensitive), 185 F₂ plants, and 48 F₂‐derived F₃ families from this cross were screened to determine inheritance of tolerance to Zn deficiency using a visual score of deficiency symptoms. The segregation ratios observed indicated that greater tolerance to Zn deficiency in ‘Skiff compared with ‘Forrest’ at the seedling stage is controlled by a single gene with no dominance. The results also indicate that visual scores are useful for genetic analysis of tolerance to Zn deficiency.     

Genetic Analysis for Partial Resistance to an Iranian Strain of Bacterial Leaf Streak (X. campestris pv. hordei) in Barley

Seven barley genotypes with high genetic variability for resistance to bacterial leaf streak (Xanthomonas campestris pv. hordei) were crossed in diallel fashion to determine the inheritance of resistance to this disease. Two experiments were undertaken in a controlled growth chamber using a complete-block design with four replicates. Each replicate consisted of a row of 20 seedlings per parent or F₁ hybrid. An Iranian strain of bacterial leaf streak was used for inoculation of 12-day-old seedlings. Results showed that the cultivars ‘Express’ and ‘Morex’ and the Iranian pure line Iran-3a had a high partial resistance in booth experiments. Diallel analysis showed highly significant general and specific combining abilities. ‘Morex’ and Iran-3a were the best combiners for partial resistance to bacterial leaf streak in barley and could be successfully used for breeding purposes.     

Net blotch resistance in wild species of Hordeum

Resistance to net blotch was evaluated in 175 Hordeum vulgare subsp. spontaneum (H. spontaneum) accessions and 149 accessions of thirteen species or subspecies of wild Hordeum. Most H. spontaneum accessions showed resistance to each of the four Pyrenophora teres f. teres (P. teres) isolates tested. However, H. spontaneum accessions showed different resistance reactions, depending upon their origin. In particular, some accessions from Afghanistan and Russia showed a high level of resistance, and accessions from Morocco were susceptible. Among the four P. teres isolates, the virulence spectra on the H. spontaneum accessions were more different between isolates from different countries than between those from the same country. Hordeum spontaneum accessions susceptible to the Canadian isolate WRS102, but resistant to the other three isolates were found in Iraq suggesting the geographical differentiation of resistance genes in H. spontaneum. All accessions of the other wild Hordeum species, especially some accessions of H. marinum subsp. gussoneanum, showed high levels of resistance. These resistance genes may be useful candidates for incorporation into cultivated barley. This revised version was published online in July 2006 with corrections to the Cover Date.     

Approaches for field assessment of resistance to leaf pathogens in spring barley varieties

The resistance of spring barley varieties to powdery mildew, leaf rust, leaf scald and net blotch was characterized by using results from inoculated small‐plot nurseries and larger survey plots subject to natural infection. The experiments were conducted in different environments. Both trial types often yielded complementary results with respect to the ranking of varieties suggesting that a recommended variety characterization should include both naturally infected survey‐type trials and nursery trials in which the most relevant pathogen isolates and/or isolate mixtures or populations are used for inoculation. Average and median values of the diseased leaf area of a variety were highly correlated with each other and with the ‘genotype main effect’ determined by joint regression analysis, whereas maximum diseased leaf area was poorly correlated with them. Statistics based on absolute disease severity values were highly correlated with the corresponding statistics derived from relative values. It is suggested that one should use at least two parameters to characterize the disease resistance of a variety, a parameter indicating the overall resistance level and a parameter indicating the potential susceptibility and/or resistance instability of a variety. For practical purposes, the genotype median and maximum, respectively, may represent these, although statistically more appropriate parameters do exist.     

Haplotype structure around the nud locus in barley and its association with resistance to leaf stripe (Pyrenophora graminea)

The naked/hulled kernel trait is controlled in barley by a single gene called nud, on chromosome 7H. The first aim of this work was use bulked segregant analysis to find, new PCR‐based markers linked to nud for marker‐assisted selection (MAS). A new SCAR marker (sJ14) was developed, which is useful for introgressing the naked trait. This, and three other SCARs, were placed on the ‘Proctor’ × ‘Nudinka’ map to detail a 0.9‐cM fragment tagging nud. In order to evaluate the haplotypes around the nud locus, a phenotypically differentiated collection of naked/hulled genotypes was characterized by means of the above markers. Eight different marker haplotypes were found in the breeding germplasm, and a new allele for the marker sKT7 was found. The same barley collection has been surveyed for resistance/susceptibility to leaf stripe (Pyrenophora graminea), in order to investigate any possible association between this and other traits. The naked/hulled seed trait was not associated with resistance/susceptibility to the fungus.