Resistance of barley genotypes to brown leaf spot

Resistance of 59 barley cultivars to three distinct isolates of Bipolaris sorokiniana, causing brown leaf spot was tested on seedlings and adult plants in a screen house and in a growth room, by determination of disease incidence, disease severity, and rate of lesion expansion. The disease reaction and severity at the seedling stage differed among cultivars. The cultivars MNS Brite, NDB 112, Kindred, Parkland, and Oderbrucke were moderately resistant to brown leaf spot, but the resistance was partial to all three isolates. None genotype with complete resistance was found. The cultivars CI 9539, Svanhals, and Chevron, considered as sources of resistance, were classified as moderately susceptible, and susceptible, respectively. Disease severity, disease reaction, and incidence of B. sorokiniana in grains also differed among the cultivars at the adult plant stage. Nevertheless, none of the genotypes was resistant to B. sorokiniana. The rate of lesion expansion differed among cultivars BR 2, MN 698, Kitchin, Svanhals, and NDB 112, with NDB 112 having the slowest expansion rate (0.194–0.205 mm²/day).     

Mature plant resistance of barley to barley leaf rust,another type of resistance

Summary Seedling and flag leaves of three barley cultivars were simultaneously inoculated with urediospores of barley leaf rust, race 1-2-1, and incubated at the same greenhouse bench. The inoculated leaves were harvested before urediospore formation was initiated. The volume of a large number of colonies was estimated by measuring colony area and colony depth by embedding the colony containing leaf segments into paraffin for microtome cutting. The colony volume was considerably smaller in flag leaves than in seedling leaves even in the extremely susceptible cultivar. On average the difference was about tenfold.     

In vitro quantification of barley reaction to leaf stripe

An in vitro technique was used to quantify the infection level of leaf stripe in barley caused by Pyrenophora graminea. This pathogen penetrates rapidly through subcrown internodes during seed germination of susceptible cultivars. Quantification was based on the percentage of the pieces of subcrown internodes that produced fungal hyphae cultured on potato dextrose agar media. The disease severity was evaluated among five cultivars with different infection levels and numerical values for each cultivar were obtained. A significant correlation coefficient (r = 0.91, P < 0.02) was found among the in vitro and field assessments. In addition, the results were highly correlated (r = 0.94, P < 0.01) among the different in vitro experiments, indicating that this testing procedure is reliable. The method presented facilitates a rapid preselection under uniform conditions which is of importance from a breeder's point of view. Significant differences (P < 0.001) were found for the length of subcrown internodes between inoculated and non‐inoculated plants with leaf stripe. Isolate SY3 was the most effective in reducing the subcrown internode length for all genotypes.     

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.     

Tolerance of spring barley cultivars to leaf rust,Puccinia hordei

Summary Fifteen spring barley cultivars were evaluated in two years for their tolerance to leaf rust, Puccinia hordei. The consistency between the results obtained in the two experiments was rather poor. The most tolerant cultivars produced low seed yields, the least tolerant ones high seed yields. A strongly negative relationship existed between harves-index and tolerance.     

Pleiotropic association of infection frequency and latent period of two barley cultivars partially resistant to barley leaf rust

Summary Cebada Capa, carrying four to six minor genes for a longer latent period (LP), was crossed to L94 and Vada, carrying no and five to six minor genes for a longer LP respectively. Of each of 68 F3-lines the infection frequency (IF) and the LP of ten just-heading plants were assessed. There appeared to be a strong association between IF and LP, whereby the relationship between IF and LP of both crosses could be described by a single linear regression equation. The data strongly suggest that the genes for increased LP pleiotropically decrease the IF. The possibility of a close linkage between genes for reduced IF and genes for increased LP, although unlikely, could not be excluded.     

Molecular mapping of the leaf rust resistance gene Rph7 in barley

Leaf rust of barley, caused by Puccinia hordei Otth, is an important foliar disease in most temperate regions of the world. Sixteen major leaf rust resistance (Rph) genes have been described from barley, but only a few have been mapped. The leaf rust resistance gene Rph7 was first described from the cultivar ‘Cebada Capa’ and has proven effective in Europe. Previously mapped restriction fragment length polymorphism (RFLP) markers have been used to determine the precise location of this gene in the barley genome. From the genetic analysis of a ‘Bow‐man’/‘Cebada Capa’ cross, Rph7 was mapped to the end of chromosome 3HS, 1.3 recombination units distal to the RFLP marker cMWG691. A codominant cleaved amplified polymorphic site (CAPS) marker was developed by exploiting allele‐specific sequence information of the cMWG691 site and adjacent fragments of genomic DNA. Based on the large amount of polymorphism present in this region, the CAPS marker may be useful for the marker‐assisted selection of Rph7 in most diverse genetic backgrounds.     

Accumulating polygenes for partial resistance in barley to barley leaf rust,Puccinia hordei. II. Field evaluation

Summary Eight lines from the cross between Vada and Cebada Capa with long to very long latent periods and four barley cultivars representing the known range of partial resistance to barley leaf rust, caused by Puccinia hordei, were evaluated in the field for partial resistance and in the greenhouse for the latent period (LP) in the young flag leaf.Each of the 12 entries was sown (15-4-1983) on a plot of 1.0 m². There were four replicates. To reduce interplot interference the plots were separated from each other by 4.0 m of spring rye. The number of urediosori per tiller was evaluated at 27-6, 4-7, 12-7 and ten days after heading. The LP was measured on 10 to 15 plants per entry in 1982 and on 10 plants in 1983.The levels of partial resistance varied greatly. The difference in number of sori per tiller between the most susceptible cultivar, Akka, and the most resistant cultivar, Vada, was about 50 times. Between Akka and the most resistant line this was approximately 5000 times. The LP's varied similarly. Vada had a LP 64% longer than that of Akka, the LP of line 26-6-11 was 15% longer. The range of partial resistance has been extended more than twofold.The correlation coefficients between LP and the level of barley leaf rust, expressed in transformed scale units, varied from -0.99 for the first sampling date to -0.97 for the third sampling date. Sampling the same development stage, ten days after heading, did not improve the r-value (r=–0.98). The LP evaluated in the young flag leaf is shown to be a very reliable criterion for partial resistance in the barley-Puccinia hordei pathosystem.Earliness tends to be associated with susceptibility. The correlation of days to heading with LP was 0.63, and with the level of barley leaf rust in the field 0.64.     

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.     

Verifying the genetic relationships between three leaf rust resistance genes in barley

Summary The genetic relationships between three known genes for resistance to Puccinia hordei in barley, Pa 3, Pa5 and Pa 7, were re-examined because of conflicting reports in the literature. PA 3 was found to be independent of Pa 5 and Pa 7, but the latter two are linked with an estimated recombination value of 7.6±1.4%. Trisomic analysis confirmed Pa 7 to be on chromosome 3, but Pa 3 could not be associated with chromosomes 3 to 7 and, therefore, is inferred to be either on chromosome 1 or 2     

Race-specific effects in major genic and polygenic resistance of barley to barley leaf rust in the field: identification and distinction

Summary Six partially resistant spring barley cultivars were exposed to four barley leaf rust (Puccinia hordei) races in the field and in the greenhouse. The 24 cultivar-race combinations were tested in field plots of 1.5×1.5 m² in two replications over two years. To reduce the interplot exchange of urediospores each plot was surrounded by winter rye.The level of barley leaf rust varied among cultivars, races and years. In both years the variance for cultivar-race interactions was highly significant and originating largely from the cultivar-race combinations Berac-22. Armelle-22, Armelle-A and Tyra-A. The Berac-22 interaction was towards higher, the other three interactions towards a lower level of barley leaf rust. The reduced rust levels of these three combinations were not due to interactions between the partial resistance of these cultivars and the aggressiveness of the races but to major genes for hypersensitivity not effective to the races 1-2-1 and F, common in Western Europe, but effective against the rare races 22 and A. This was revealed in the greenhouse experiments where all combinations had a susceptible infection type except Armelle-22, Armelle-A and Tyra-A, which showed low infection types in both the seedling and adult plant stages. The urediosori present in the field plots of these three combinations apparently arose from spores derived from other plots; this interplot interchange suggesting partial resistance.The interaction of Berac with race 22 truly was a small race-specific effect within the polygenic, partial resistance of barley to barley leaf rust like the one reported before between Julia and race 18.     

Partial resistance of barley to leaf rust,Puccinia hordei. III. The inheritance of the host plant effect on latent period in four cultivars

Summary The latent period (LP) in the barley-leaf rust relationship is an important component of the partial resistance complex. The inheritance of the host plant effect on LP was studied in five crosses between four cultivars. The LP, effectuated by the susceptible cultivars L94 and L92, were 8.0 and 8.6 days resp., those of the resistant cultivars Minerva (Mi) and Vada (Va) 16.9 and 17.1 days resp. The mean F₁ and F₂ values of the crosses L92×L94 and Mi x Va were intermediate between the parental ones. The variances of the F₂'s were slightly larger than those of the parents and the F₁'s indicating some segregation. In the crosses between a susceptible and a resistant cultivar the F₁ value was half way between the mid-parent and susceptible parent value. The F₂ mean lay approximately half way between the mid-parent and F₁ value, with a distribution positively skewed and slightly bimodal. There was no transgression, in fact not even the parental values were recovered among nearly 500 F₂ plants. The F₃-lines of the crosses between susceptible and resistant cultivars showed within line variances from as low as the parental values to as high as or higher than those of the F₂. In hte F₃'s the parental values could be recovered although no transgression occurred.L94 is supposed to carry no genes effecting a longer LP. The long LP of Mi and Va, assuming no linkage, is thought to be effectuated by the cumulative action of a recessive gene with a fairly large effect and some four to five minor genes with additive inheritance. One of these minor genes is supposed to be carried by L92, while Mi and Va are thought to differ for one minor gene only. In case linkage exists, the number of minor genes involved could be higher.     

The barley mutant emr2 shows enhanced resistance against several fungal leaf pathogens

Homozygous mlo -barley plants are resistant to barley powdery mildew but hypersusceptible to the rice blast fungus Magnaporthe oryzae . A mutational analysis was performed in the barley back-cross line BCIngrid mlo5 which led to the identification of two mutants with enhanced capacity to resist infections by M. oryzae , referred to as enhanced M. oryzae resistance mutants emr1 and emr2 . Here, we report on the characterization of emr2 mutant plants which not only show an almost complete reduction in disease severity after inoculation with M. oryzae but are also resistant to the necrotrophic fungi Drechslera teres and Rhynchosporium secalis . Histological analysis revealed that resistance to M. oryzae was based mainly on the formation of papillae at sites of attempted penetration into epidermal cells. There was no progression of fungal growth into the mesophyll. Additionally, because of the presence of the mlo -allele, emr2 -plants retained resistance to powdery mildew. The emr2 -conditioned broad spectrum resistance was inherited as in a recessive manner. Monitoring of PR -gene expression and enzymatic activity of peroxidases revealed a constitutively activated defence in emr2 .     

Mining the global diversity of barley for Fusarium resistance using leaf and spike inoculations

Fusarium graminearum is a devastating fungal pathogen that causes significant yield and quality losses in cereals. We utilized a diversity set of barley (140 genotypes) to explore vital resistance alleles against this aggressive pathogen. The resistance assessment was carried out on spikes and leaves via artificial inoculations under control conditions. The phenotypic data was subjected to genome-wide association analysis using a genetic map based on DArT and SNP markers. This analysis revealed eleven and nine marker trait associations for leaf disease scoring (LDS) and spike disease scoring (SDS), respectively. The strongest QTL for LDS was found on chromosome 1H where a minor allele of wild origin decreased disease symptoms by 78%. The major QTL allele for SDS was linked with marker locus SCRI_RS174710 on chromosome 5H. In addition, four favorable epistatic interactions effects were found in decreasing disease symptoms. Overall, three QTL were common for LDS and SDS, which indicates a partial genetic relatedness of these resistances in barley. The QTL alleles for LDS and SDS will help to establish organ specific resistances in cultivated barley.     

Localization of a resistance gene and identification of sources of resistance to barley leaf stripe

In order to determine more precisely the location of the barley leaf stripe gene, called the ‘Vada-resistance gene’, on barley chromosome 2, 63 chromosome-doubled barley lines were tested. Using data on known chromosome 2 genetic markers, the ‘Vada-resistance gene’ was estimated to be located between the markers MSU21 and Xris45b, and at a distance of about 20% recombination from the powdery mildew resistance gene MILa. We suggest that the ‘Vada-resistance gene’ is designated Rdg1a and that all former leaf stripe resistance gene designations should be rejected. To identify possible new sources of resistance, 11 barley cultivars/lines known to possess leaf stripe resistance and originating from different parts of the world, were tested with one Danish and two Syrian isolates of the leaf stripe fungus. Three apparently genetically different sources of race-specific resistance were found. The ‘Vada-resistance’ in the cultivar ‘Golf was effective against seven out of eight isolates’ populations of the leaf stripe fungus differing in geographical origin.     

玫瑰花抗氧化活性研究

通过对不同提取溶剂、不同提取温度、不同提取时间和不同提取pH值等方面研究了不同条件对玫瑰花(Rosa hybriad cv.Cardinal)清除DPPH能力的影响.结果表明,沸水的提取效率比其他提取方法更有效,其提取液对DPPH的清除率显著强于其他提取液(P＜.05).100℃沸水提30min是最优提取条件,延长提取时间不会有效提高提取液对DPPH的清除能力(P＜0.05).然而,pH值明显影响提取液对DPPH的清除能力,pH值为5时,提取液的清除能力最强,碱性条件下提取液的清除能力明显减弱.同时,提取液对DPPH的清除能力与多酚含量有关,提取液浓度与DPPH清除率呈一定的线性关系(y=157.92x 14.745,R=0.9914).     

Partial resistance of barley to leaf rust,Puccinia hordei. V. Analysis of the components of partial resistance in eight barley cultivars

Summary Eight spring barley cultivars, respresenting the known range in partial or slow rusting resistance to leaf rust, Puccinia hordei, were investigated for their effects on the components of partial resistance; infection frequency, latent period, infectious period and spore production per uredosorus per day. Considerable variation was observed among the cultivars for each of the components. The cultivar effects on the components tend to be associated. Cultivar L94 for instance, shows the highest infection frequency, the shortest latent period and a long infectious period. Julia and Vada both have a low infection frequency, a long latent period and a low spore production per sorus per day. This association, though, is only a partial one.The total spore production per unit leaf area (the combined result of the four components) appeared highly correlated with the partial resistance in the field (r=0.85). Only a relatively small portion of the variation in partial resistance cannot be explained by the four components studied. Several other aspects, which might affect the rate of epidemic development, are discussed.Latent period, measuring the onset of the new spore production, estimated partial resistance as well as total spore production did (r=–0.85). In order to evaluate the partial resistance of barley genotypes in the greenhouse the latent period is preferred above total spore production as it is measured more easily, more accurately and sooner after inoculation.