Plum pox virus (PPV) is responsible for sharka disease, one of the most detrimental stone fruit diseases affecting Prunus trees worldwide. Only a few apricot cultivars have been described as resistant, most originating from North American breeding programmes. Several PPV resistance quantitative trait loci (QTLs) have been mapped in various progenies, consistently highlighting the contribution to the resistance of the upper part of linkage group 1 (LG1). However, to date, no consensus has been reached on the precise number of QTLs linked to the resistance to PPV in apricot and P. davidiana or on their accurate position on the genetic linkage map. In the present study, the quantitative resistance of cultivar 'Harlayne' was analysed over five growth periods in a large F1 population. Four QTLs were identified, three mapping on LG1, explaining between 5% and 39% of the observed phenotypic variance. In an effort to further this analysis of PPV resistance in apricot, these results were merged in a single QTL meta-analysis with those of five other PPV resistance analyses available in the literature. Three consensus QTL regions were identified on LG1 and a putative fourth region on LG3. QTL meta-analysis also revealed the contribution of each resistant cultivar to metaQTLs, providing interesting comparative data on the resistance factors shared between the resistance sources used in the various studies. Finally, it was shown that one of the metaQTLs co-localizes with the eukaryotic translation initiation factor eIF4E, thus providing new hypotheses on the mechanisms of PPV resistance in apricot.

Plum pox virus (sharka; PPV) can cause severe crop loss in economically important Prunus species such as peach, plum, apricot, and cherry. Of these species, certain apricot cultivars ('Stark Early Orange', 'Goldrich', 'Harlayne') display significant levels of resistance to the disease and are the genetic substrate for studies of several xlaboratories working cooperatively to genetically characterize and mark the resistance locus or loci for marker-assisted breeding. The goals of the work presented in this communication are the characterization of the genetics of PPV resistance in 'Stark Early Orange' and the development of co-dominant molecular markers for marker-assisted selection (MAS) in PPV resistance breeding. We present the first genetic linkage map for an apricot backcross population of 'Stark Early Orange' and the susceptible cultivar 'Vestar' that segregates for resistance to PPV. This map is comprised of 357 loci (330 amplified fragment length polymorphisms (AFLPs), 26 simple sequence repeats (SSRs), and 1 morphological marker for PPV resistance) assigned to eight linkage groups. Twentytwo of the mapped SSRs are shared in common with genetic reference map for Prunus (T × E; Joobeur et al. 1998) and anchor our apricot map to the general Prunus map. A PPV resistance locus was mapped in linkage group 1 and four AFLP markers segregating with the PPV resistance trait, identified through bulk segregant analysis, facilitated the development of SSRs in this region.

No abstract

Plum pox virus (PPV) is a potyvirus that causes sharka disease in infested stone fruit trees (Prunus species, peach, apricot, plum). In apricots, the resistance is controlled by a major quantitative trait locus that explains up to 70% of the phenotypic variance; it is localised in the upper part of linkage group 1. In this report, we transformed candidate genes that mapped in the region of the apricot resistance locus into polymerase chain reaction markers (SSCP and SSR) and tested for their co-localisation with the major PPV resistance locus in related and unrelated populations. Three populations of F1 and F2 individuals issued from crosses between the PPV-resistant cultivar 'Stark Early Orange' or 'Goldrich' and three susceptible parents were used in this study. Molecular-marker data were collected to determine the linkage relationship between the PPV resistance locus in apricots and markers that target candidate disease-resistance genes. In addition, SSR markers linked to resistance-gene candidates were mapped to positions flanking the PPV resistance locus in different apricot populations. Therefore, we demonstrate that this strategy helps to saturate the major genomic region controlling resistance to PPV in apricot with valuable codominant markers.

Individuals of Apera spica-venti populations tested in this study possess the target-site ALS resistance mutation and an additional so far unknown resistance mechanism(s).

A complex of Fusarium spp. causes Fusarium head blight (FHB) on wheat and also on barley. Infection with FHB results not only in yield loss, but also causes depreciation of the harvested product due to the accumulation of toxins such as deoxynivalenol produced by Fusarium spp. The flowering time is a very susceptible period for primary infection. One reason might be that during this period spores can get into the opened wheat florets where they may later cause infection. Initial symptoms of infection of a wheat ear are visible whitening and drying of individual spikelets or entire parts of the ear. If the florets became infected shortly after blooming, grains are often not formed, while other infected spikelets have grains with various deformities, shrunken and with pink-white coloration (Klem & Tvarůžek 2005). The main aim of experiments was detection of Fusarium species on wheat grains by using of the PCR methods. Abstract Nedělník J., Moravcová H., Hajšlová J., Lancová K., Váňová M., Salava J. (2007): Fusarium spp. in wheat grain in the Czech Republic analysed by PCR method. Plant Protect. Sci., 43: 135-137. The frequency of occurrence of four Fusarium spp. on wheat in the Moravia region, Czech Republic, was determined by polymerase chain reaction (PCR). Grain samples were collected during 2003-2006 at grain purchase centres. The dominant species was F. graminearum, which was recorded in all samples of the first 3 years of the study and in 88% of them in 2006. The previously more frequent F. culmorum was detected in 100% of the samples only in 2005; in the preceding two years the frequency of its detection was lower, 84% and 60%, and in 2006 it was detected in 55% of the samples. Fusarium avenaceum had a very low occurrence in the years 2003-2004, but in 2005 it was recorded in 100% of the samples. In 2006 it was the opposite-total absence of this species. A quite different situation was found in the occurrence of the fourth species-F. poae. In the years 2005 and 2006 it was only detected in 10%, resp. 2% of the samples, compared to markedly higher occurrences in the previous years. A comparison of the current weather development with the long-term mean at the Troubsko locality suggests that years with a relatively long, wet and cold start of the growing season and warmer end of vegetation (late May-July) will favour F. graminearum.

Both RFLP and Bi-PASA were suitable for detecting resistance alleles to pyrethroids, and in most cases also for detecting resistance alleles to organophosphates. In contrast to Bi-PASA, RFLP was also suitable for samples with lower DNA quality when testing for the resistance allele to pyrethroids. On the other hand, RFLP was not as accurate as Bi-PASA in detection of the organophosphate resistance allele.

Smallanthus sonchifolius is a periennal herb originally cultivated in South America and now grown in several other countries. Recently, greater attention has been focused on this plant due to its agronomical, nutritional and pharmacological characteristics. In this paper the application of RAPDs and AFLPs for the analysis of genetic diversity in a group of 5 Smallanthus sonchifolius landraces is presented. Both methods proceed through the direct analysis of DNA, and their results were compared with the total phenolic content of each landrace and its morphological traits. Using 61 RAPD primers, 85 informative bands were identified, corresponding to 28.7% of polymorphism. In comparison, only six selected AFLP primer pairs produced 84 informative bands, with a similar percentage of polymorphism (23.4%). RAPD and AFLP markers were analyzed separately. Total phenolic content varied twofold among the five landraces analysed, ranging from 3,494 to 6,849 mg/g. Each type of molecular marker resolved two main groups that included the same genotypes, but with different within-group relationships among genotypes. The two groups are consistent with some phenotypic characters but they do not reflect faithfully their geographical origin. Most notably, the two groups comprise landraces with higher and lower total phenolic content, respectively. Dendrograms based on the two molecular data sets graphically depicted the ability of both methods to differentiate all the cultivars studied. Data obtained suggest that the two molecular markers applied are useful to investigate intra-specific genetic variability in Smallanthus sonchifolius, and predict well the total phenolic content of each landrace.