Bai, G.-H., Kolb, F. L., Shaner, G., and Domier, L. L. 1999. Amplified fragment length polymorphism markers linked to a major quantitative trait locus controlling scab resistance in wheat. Phytopathology 89:343-348. Scab is a destructive disease of wheat. To accelerate development of scab-resistant wheat cultivars, molecular markers linked to scab resistance genes have been identified by using recombinant inbred lines (RILs) derived by single-seed descent from a cross between the resistant wheat cultivar Ning 7840 (resistant to spread of scab within the spike) and the susceptible cultivar Clark. In the gree nhouse, F5, F6, F7, and F10 families were evaluated for resistance to spread of scab within a spike by injecting about 1,000 conidiospores of Fusarium graminearum into a central spikelet. Inoculated plants were kept in moist chambers for 3 days to promote initial infection and then transferred to greenhouse benches. Scab symptoms were evaluated four times (3, 9, 15, and 21 days after inoculation). The frequency distribution of scab severity indicated that resistance to spread of scab within a spike was controlled by a few major genes. DNA was isolated from both parents and F 9 plants of the 133 RILs. A total of 300 combinations of amplified fragment length polymorphism (AFLP) primers were screened for polymorphisms using bulked segregant analysis. Twenty pairs of primers revealed at least one polymorphic band between the two contrasting bulks. The segregation of each of these bands was evaluated in the 133 RILs. Eleven AFLP markers showed significant association with scab resistance, and an individual marker explained up to 53% of the total variation ( R 2 ). The markers with high R 2 values mapped to a single linkage group. By interval analysis, one major quan titative trait locus for scab resistance explaining up to 60% of the genetic variation for scab resistance was identified. Some of the AFLP markers may be useful in marker-assisted breeding to improve resistance to scab in wheat.

https://apsjournals.apsnet.org/doi/pdfplus/10.1094/PHYTO.1999.89.4.343

Amplified fragment length polymorphism markers linked to a major quantitative trait locus controlling scab resistance in wheat.

Doubled Haploid Production in Crop Plants

The aim of this study was the improvement of a genetic map of the F1 population from the cross between the fungus-resistant grapevine cv. “Regent” and the susceptible cv. “Lemberger” and its use to localize factors affecting pathogen resistance and leaf morphology. To construct an integrated map combining the information from both parental meiotic recombination frequencies co-dominant microsatellite markers were employed. 
Resistance gene analog (RGA)-derived and sequence characterized amplified regions (SCAR) markers correlated with powdery and downy mildew resistance were additionally mapped. The new integrated map contains 398 markers aligned along 19 linkage groups, covers a total length of 1,631 cM and shows an average distance between markers of 4.67 cM. 
One hundred and twenty-two microsatellite markers were newly mapped. This genetic map was used to localize QTLs (quantitative trait loci) conferring resistance to powdery and downy mildew pathogens transmitted from “Regent”. Factors influencing specific leaf morphology traits were identified in addition. A major QTL for powdery mildew resistance and one major and one minor QTL for downy mildew resistance were detected. Some RGA-derived markers are found co-located in the region covered by the major QTL for resistance to downy mildew hinting at their putative functional relevance. Furthermore, 27 QTLs affecting leaf morphology descriptors were identified. This map is an important tool for grapevine breeding and resistance research.

Genetic mapping and localization of quantitative trait loci affecting fungal disease resistance and leaf morphology in grapevine (Vitis vinifera L)

The density and utility of the molecular genetic linkage map of cultivated sunflower (Helianthus annuus L.) has been greatly increased by the development and mapping of several hundred simple sequence repeat (SSR) markers. Of 1089 public SSR markers described thus far, 408 have been mapped in a recombinant inbred line (RIL) mapping population (RHA280 × RHA801). The goal of the present research was to increase the density of the sunflower map by constructing a new RIL map (PHA X PHB) based on SSRs, adding loci for newly developed SSR markers to the RHA280 × RHA801 RIL map, and integrating the restriction fragment length polymorphism (RFLP) and SSR maps of sunflower. The latter was accomplished by adding 120 SSR marker loci to a backbone of 80 RFLP marker loci on the HA370 x HA372 F 2 map. The map spanned 1275.4 centimorgans (cM) and had a mean density of 6.3 cM per locus. The PHA x PHB SSR map was constructed from 264 SSR marker loci, spanned 1199.4 cM, and had a mean density of 4.5 cM per locus. The RHA280 × RHA801 map was constructed by adding 118 new SSR and insertion-deletion (INDEL) marker loci to 459 previously mapped SSR marker loci. The 577-locus map spanned 1423.0 cM and had a mean density of 2.5 cM per locus. The three maps were constructed from 1044 DNA marker loci (701 unique SSR and 89 unique RFLP or INDEL marker loci) and supply a dense genome-wide framework of sequence-based DNA markers for molecular breeding and genomics research in sunflower.

Towards a Saturated Molecular Genetic Linkage Map for Cultivated Sunflower

Species of the coelomycetous genus Phoma are ubiquitously present in the environment, and occupy numerous ecological niches. More than 220 species are currently recognised, but the actual number of taxa within this genus is probably much higher, as only a fraction of the thousands of species described in literature have been verified in vitro. For as long as the genus exists, identification has posed problems to taxonomists due to the asexual nature of most species, the high morphological variability in vivo, and the vague generic circumscription according to the Saccardoan system. In recent years the genus was revised in a series of papers by Gerhard Boerema and co-workers, using culturing techniques and morphological data. This resulted in an extensive handbook, the ?Phoma Identification Manual? which was published in 2004. The present review discusses the taxonomic revision of Phoma and its teleomorphs, with a special focus on its molecular biology and papers published in the post-Boerema era.

Biology and recent developments in the systematics of Phoma, a complex genus of major quarantine significance

Partial resistance to downy mildew (Plasmopara halstedii) and to black stem (Phoma macdonaldii) in sunflower were investigated under natural field infection and a controlled growth chamber respectively. Genetic control for resistance to the diseases was determined in recombinant inbred lines (RILs) and their two parents, ’PAC-2’ and ’RHA-266.’ The experiments were undertaken in a randomized complete block design with two replications, in a field severely infected by downy mildew and in a controlled growth chamber with plants inoculated with an agressive French isolate of P. macdonaldii. Each replication consisted of three rows, 4.6-m long, giving 48 plants per RIL or parent in the field and 15 plants in the growth chamber. Genetic variability was observed among the RILs for resistance to both diseases. When 10% of the selected RILs were compared with the mean of the two parents genetic gain was significant for partial resistance to the diseases. Four putative QTLs for resistance to downy mildew on linkage groups 1, 9 and 17 were detected using composite interval mapping. The QTLs explained 54.9% of the total phenotypic variance. Major QTLs (dmr1–1 and dmr1–2) for resistance were found on linkage group 1 with up to 31% of the phenotypic variability explained by two peaks. QTL analysis of resistance to black stem showed seven QTLs on linkage groups 3, 6, 8, 9, 11, 15 and 17. The detected QTLs together explain 92% of the phenotypic variation of the trait. Crosses between RILs contrasted for their resistance to downy mildew and black stem, and exhibiting molecular polymorphism in detected QTLs, will be made in order to focus more-precisely on the genomic region of interest.

/pdf/a-qtl-analysis-of-sunflower-partial-resistance-to-downy-n725mw1865.pdf

A QTL analysis of sunflower partial resistance to downy mildew ( Plasmopara halstedii) and black stem ( Phoma macdonaldii) by the use of recombinant inbred lines (RILs).

Growth of 17 isolates of Phoma macdonaldii, the causal agent of sunflower black stem, was investigated for response to pH and temperature, and for morphology and asexual morphogenesis (pycnidiogenesis and pycnidium size). For all isolates, the optimum pH for growth was between 4 and 5, and the optimum temperature varied between 20 and 30°C and radial growth was slowest at 5 and 35°C. Significant differences in the number and size of pycnidia were observed between isolates. Pycniospore germination was investigated under various conditions in five isolates chosen for their geographical origins, pigmentation, optimum growth temperature and pycnidiogenesis. Increasing the concentration from 106 to 107 pycniospores per mL decreased the germination rate. The optimum temperature for pycniospore germination varied between 15 and 30°C, depending on the isolate, and the optimum and maximum pH values were 5 and 7, respectively. The optimum and minimum relative humidities allowing pycniospore germination were 100 and 95%, respectively. Pycniospore germination was photo-independent. An artificial inoculation method was developed and the aggressiveness of the pathogen was assessed on a susceptible sunflower cultivar, using a 1–9 scale that integrated the percentage of necrotic area on the cotyledon petiole at the stage when the first pair of leaves was fully developed. Significant differences in aggressiveness were observed among the 17 isolates. The parameters investigated clearly suggest the occurrence of a wide phenotypic variability in Phoma macdonaldii.

Phenotypic variability of Leptosphaeria lindquistii (anamorph: Phoma macdonaldii), a fungal pathogen of sunflower

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.

Inheritance of partial resistance to spot blotch in barley.

Isolates of Drechslera teres that cause net or spot-type symptoms on barley (Hordeum vulgare) were collected in 1986 and 1987 from fields in different regions of France. Variations in pathogenicity were evaluated using 12 barley cultivars. The Middle-Eastern cultivars Arrivate and 79-S10-10 were resistant to all isolates except R5 and S5. The Ethiopian cultivar C1 5791, previously reported to be resistant, was susceptible to the R5 and S5 biotypes. There was a high correlation coefficient between the classification of cultivars for resistance to D. teres f. sp. teres and D. teres f. sp. maculata. A method for conserving the virulence of the isolates on straw is evaluated. The virulence level of the isolates was the same after 4 years of storage using this method.

Variation in the resistance of barley cultivars and in the pathogenicity of Drechslera teres f. sp. maculata and D. teres f. sp. teres isolates from France

Two programmes to investigate the inheritance of resistance to black stem in sunflowers were undertaken in a controlled-environment growth chamber. In the first, an experiment was performed using a randomized complete block design with 24 lines, six male-sterile (A lines), six maintainers (B lines), six restorers (R lines) and their six F1 hybrids in six replications. Each treatment consisted of 12 seedlings. Twelve-day-old seedlings were inoculated with a suspension of pycniospores, and 7 days later the two cotyledon petioles of each seedling were scored on a 1–9 scale for the percentage of necrotic area. Some alloplasmic lines (which have the same nucleus and different cytoplasms) gave a significant cytoplasmic effect for improved partial resistance to the disease. Deviation of F1 hybrids from the mean of the parent values was significant for partial resistance to Phoma macdonaldii in three of the six F1 hybrids. Two further experiments with eight lines (resistant and susceptible) at the fifth leaf-pair and flowering stages were carried out under the same conditions. At both growth stages the previous classification of lines at the seedling stage was confirmed. In the second programme, five male-sterile sunflower lines were crossed with five fertility-restorers in a factorial mating design. The 10 inbred lines and their 25 F1 hybrids were studied in two successive experiments under the same conditions and with the same experimental design and isolate of Phoma as in the seedling-stage experiment in the first programme. Analysis of variance showed that male-sterile and restorer lines possessed general combining abilities, and also that specific combining abilities of F1 hybrids were significant. The estimates of general combining ability for partial resistance were significant in AS617A, AS618A and AS614R inbred lines. These lines are available for developing F1 hybrids with improved resistance to Phoma in sunflower-breeding programmes.

G. Barrault

Papers

A QTL analysis of sunflower partial resistance to downy mildew ( Plasmopara halstedii) and black stem ( Phoma macdonaldii) by the use of recombinant inbred lines (RILs).

Phenotypic variability of Leptosphaeria lindquistii (anamorph: Phoma macdonaldii), a fungal pathogen of sunflower

Inheritance of partial resistance to spot blotch in barley.

Variation in the resistance of barley cultivars and in the pathogenicity of Drechslera teres f. sp. maculata and D. teres f. sp. teres isolates from France

Inheritance of partial resistance to black stem (Phoma macdonaldii) in sunflower