Felicity Vear - Academia.edu (original) (raw)
Papers by Felicity Vear
Inheritance of 'Hullability' in Sunflowers (Helianthus annuus L.)
Plant Breeding, Aug 1, 1994
Improvement of the feed value of sunflower seedmeal by hulling achenes before crushing is of econ... more Improvement of the feed value of sunflower seedmeal by hulling achenes before crushing is of economic importance and varieties with good ‘hullability’ (ease of hulling) would be economically significant. Knowledge of the genetics of this characteristic is therefore necessary. Studies of heritability were made on a factorial cross of six female and six restorer lines. Hullability was measured as the ratio of hull removed by a laboratory huller against the total quantity of hull in the achene. The genotypes studied showed a wide range of hullabilities. There were considerable environmental effects but only small interactions; correlations between results in different locations were significant. Additive genetic effects predominated, although there were some interactions between parental lines. Narrow‐sense heritabilities were 0.73–0.85 for genotype means, 0.52 when calculated from individual plants, and 0.36–0.76 from parent‐progeny regressions. Early selection based on progeny means or a combination of individual and progeny values would appear to be the best method of breeding for improved hullability of sunflower achenes.
Euphytica, 1994
To study the genetic control of hullability in sunflower (Helianthus annuus L.), 36 hybrids, prod... more To study the genetic control of hullability in sunflower (Helianthus annuus L.), 36 hybrids, produced by a factorial cross of six male sterile and six restorer lines, were evaluated in two locations in Spain and one in France. Hullability was calculated as the ratio of the quantity of hull removed by a mechanical huller compared with total hull content. In dry conditions in Spain, hullability was twice (83 .1%) that observed in France (41 .5%). In all locations, male, female and interaction effects were significant. Estimates of narrow sense heritability varied between 0 .78 and 0.82, values similar to those for other seed characters such as oil content. There were positive genetic and phenotypic correlations between hullability and 1000 seed weight (means 0 .81 and 0.74, respectively) but negative correlations with seed oil content (-0 .73 and-0 .68, respectively). It is concluded that selection in early segregating generations of crosses involving good hulling material needs a specific strategy in order to maintain reasonable levels of oil and protein contents in the seed of the selected genotypes .
Variation of hullability and other seed characteristics among sunflower lines and hybrids
Euphytica, 1996
The hullabilities of 40 inbred lines (20 male sterility maintainers and 20 male fertility restore... more The hullabilities of 40 inbred lines (20 male sterility maintainers and 20 male fertility restorers) and 36 hybrids were studied in several environments in France. Thousand seed weight, oil and hull contents and the quantity of hulls remaining with the kernel after hulling were also measured. Principal component analyses and a hierarchical clustering method were used to described the variation of both inbreds and hybrids. Hullability varied from 11 to 66% for inbreds and 16 to 60% for hybrids. This variation is sufficient to permit breeding programmes for this character. Hullability is correlated positively with hull content (r=0.35* to 0.69*) but negatively with oil content (r=-0.34*to-0.71**). Large seeds generally hull better than small seed (r=0.21ns to -0.66**). The value of the different classes of genotypes is discussed. Inbreds and hybrids producing achenes with a quite small hull content, a high oil content but a good hullability are the most promising for improvement of the quality of sunflower seed meal. Such genotypes are rare so that a recurrent selection programme is recommended to increase the frequency of favorable genes.
La carte génétique du tournesol : le programme CARTISOL
HAL (Le Centre pour la Communication Scientifique Directe), 1994
A l'heure du sequencage du genome d'Arabidopsis (si important pour le Golza), ou en est l... more A l'heure du sequencage du genome d'Arabidopsis (si important pour le Golza), ou en est l'etablissement de la carte genetique du tournesol et la recherche des marqueurs moleculaires de resistance aux maladies, utilisables en selection?
Assessment of inter- and intra-inbred line variability in sunflower (Helianthus annuus) by RFLPs
Genome, Oct 1, 1995
The restriction fragment length polymorphism (RFLP) between 26 sunflower inbred lines was evaluat... more The restriction fragment length polymorphism (RFLP) between 26 sunflower inbred lines was evaluated with 81 probe–enzyme combinations involving 51 cDNA clones and 4 restriction enzymes (HindIII, EcoRI, EcoRV, and BglII). An average of 4.6 fragments and 4.9 profiles was detected per probe–enzyme combination, across all inbred lines. The RFLPs revealed were characterized by a high percentage (>70%) of multifragment profiles. Nei's average gene diversity was calculated to measure the genetic variability within cultivated sunflower; the average gene diversity computed with 81 probe–enzyme combinations was 0.59. The relationships between the 26 sunflower inbred lines were analysed by estimates of Nei's F index, which ranged from 0.50 to 0.91, as well as Nei's genetic distance, d, which varied from 0.05 to 0.41. A UPGMA (unweighted pair-group arithmetic average clustering) dendrogram was constructed using the genetic distance matrix; likewise, a principal component analysis was performed using the F matrix. The results obtained from the two clustering analyses allowed the separation of maintainer lines (females) from restorer lines (males). After partitioning the 26 lines into a pool of maintainer lines and a pool of restorer lines, the estimation of gene differentiations showed that the absolute difference (Dm) between females and males was only about 5%. Intraline variability was also examined in 4 sunflower inbred lines, using 30 probe–enzyme combinations. Heterogeneity at varying levels was detected in 3 of the 4 lines studied. The RFLPs detected by this set of selected clones in the 26 inbred lines suggests that RFLPs could be very useful descriptors for sunflower inbred line and variety studies.Key words: RFLPs, sunflower, inbred lines, genetic diversity.
HAL (Le Centre pour la Communication Scientifique Directe), 1989
— L'évolution de l'humidité du capitule et des graines de 25 variétés de tournesol (Heliant... more — L'évolution de l'humidité du capitule et des graines de 25 variétés de tournesol (Helianthus annuus L.), de la teneur en huile de 13 d'entre elles et du poids sec de 100 grains, pour 10 d'entre elles, ont été suivis de la floraison jusqu'à la maturité complète. L'humidité des graines diminue régulièrement au cours des 7 semaines d'étude à des vitesses différentes suivant les variétés. L'humidité du capitule ne varie pas pendant les 6 premières semaines après la floraison (70 à 80% d'eau), puis décroît de façon plus ou moins importante suivant les variétés. Un certain nombre de corrélations entre différents caractères et l'humidité au 2 septembre sont établies. Le contenu maximal en huile varie, suivant les variétés, de 44 à 52% du poids sec du grain. Il est élaboré, en moyenne, dans les 40 premiers jours après la floraison, la matière sèche du grain l'étant dans les 45 premiers jours après la floraison. Les vitesses d'évolution des teneurs en huile et en matière sèche varient en fonction des génotypes. dessèchementmatière sècheteneur en huile-maturité physiologique Summary — Changes in characteristics of sunflower seed and capitula during ripening. Changes in the humidity of capitula and seed of 25 sunflower (Helianthus annuus L.) varieties were followed from flowering to maturity, the oil content evolution was studied for 13 varieties and the 100 grain weight evolution for 10. The water content of seeds diminished regularly during the 7 weeks of the study, with significant varietal rate differences. The capitulum humidity did not vary during the six first weeks after flowering (70 to 80°/) but then was reduced to a variable extent according to variety. Correlation between different characters and humidity on 02109187 were established. The maximum oil content of the seed varied between varieties from 44 to 52°/ of dry weight. It was generaly produced during the 40 days after flowering, comparable with the dry weight, maximum 45 days after flowering days. The rates of increase of both these characteristics varied according to genotype.
The genetic control in sunflower
HAL (Le Centre pour la Communication Scientifique Directe), Dec 3, 1991
Attaque de Sclerotinia sclerotiorum sur bourgeon terminal du tournesol (Helianthus annuus). Symptômes épidémiologie et résistance
HAL (Le Centre pour la Communication Scientifique Directe), Jul 28, 1993
La selection du tournesol en France : l'age adulte
HAL (Le Centre pour la Communication Scientifique Directe), 1990
Helianthus
Springer eBooks, Sep 24, 2010
ABSTRACT Helianthus annuus the sunflower, originates from North America, where about 40 species b... more ABSTRACT Helianthus annuus the sunflower, originates from North America, where about 40 species belonging to the same genus grow wild. Ever since modern breeding programs started in the 1960s to develop hybrid varieties, wild species have been found to be useful sources of agronomic characters. Annual species with the same chromosome number as sunflower have provided cytoplasmic male sterility, restorer, and downy mildew resistance genes. Modern research addresses the possibility of introducing characters from hexaploid, perennial Helianthus species.
The use of isozyme polymorphism for identification of sunflower (Helianthus annuus) inbred lines
HAL (Le Centre pour la Communication Scientifique Directe), 1992
Le pollen, facteur d'attraction des pollinisateurs vers le tournesol (Helianthus annuus L.)
International audienc
Les varietes de tournesol cultivees actuellement ont un rendement en graines moyen de 153% des pr... more Les varietes de tournesol cultivees actuellement ont un rendement en graines moyen de 153% des premiers hybrides des annees 1970 ; le gain potentiel en rendement de plus de 1% par an se maintient. Il y a egalement eu un gain de teneur en huile d'environ 1.5 points, par rapport aux 20 ans precedents. Le genre Helianthus etant forme de 50 especes, dont le tournesol sauvage et d'autres especes annuelles qui se croisent facilement avec les genotypes cultivees, certaines des ressources genetiques cultivees peuvent etre des introgressions volontaires ou non. Les gains en rendement, quantitatifs et polygeniques sont probablement issus de tournesol cultive jusqu'a present, tandis que des changements qualitatifs viennent des especes sauvages, les plus importants etant la sterilite mâle cytoplasmique, la restauration, la ramification et des resistances au mildiou et a l'orobanche. Les possibles apports futurs de ces ressources au progres varietal sont discutes.
The sunflower diseases for which publications are most frequent are Sclerotinia, downy mildew, br... more The sunflower diseases for which publications are most frequent are Sclerotinia, downy mildew, broomrape and Phomopsis. Resistance breeding has so far been concerned with either major gene resistance (downy mildew, broomrape) or quantitative resistance (Sclerotinia, Phomopsis). With major genes, resistance has been complete but not durable. Although new genes are regularly found, they are quite rapidly overcome. For quantitative resistance, although progress has been quite rapid in the case of Phomopsis, it has been slow for Sclerotinia and some research has concerned the possibility of genetic transformation. For efficient disease control in the future, it is proposed that, when available, vertical and horizontal resistances should be combined and if this is not the case, marker-assisted selection should be used to combine QTLs with different and additive defence mechanisms.
MARKER OF RESISTANCE TO $i(SCLEROTINIA SCLEROTIORUM)
OCL, 2016
This article discusses changes in sunflower breeding objectives since the introduction of hybrid ... more This article discusses changes in sunflower breeding objectives since the introduction of hybrid varieties 50 years ago. After a reminder of the importance of some early programmes, Canadian in particular, the present situation for each breeding objective is compared with those encountered earlier. Breeding for yield has changed from maximum possible yield under intensive agriculture to yield with resistance to abiotic stresses, moderate droughts and shallow soils in particular, helped by collaboration with agronomists to produce crop models. Breeding for oil has changed from quantity to quality and the value of seed meal is again becoming economically important. Necessary disease resistances vary with agronomic practises and selection pressure on pathogens according to varietal genetics. The possibilities of new types of sunflower are also discussed. Advances in genomics will change breeding procedures, but with rapidly changing molecular techniques, international collaboration is particularly important.
Helianthus
Wild Crop Relatives: Genomic and Breeding Resources, 2010
ABSTRACT Helianthus annuus the sunflower, originates from North America, where about 40 species b... more ABSTRACT Helianthus annuus the sunflower, originates from North America, where about 40 species belonging to the same genus grow wild. Ever since modern breeding programs started in the 1960s to develop hybrid varieties, wild species have been found to be useful sources of agronomic characters. Annual species with the same chromosome number as sunflower have provided cytoplasmic male sterility, restorer, and downy mildew resistance genes. Modern research addresses the possibility of introducing characters from hexaploid, perennial Helianthus species.
Molecular Plant Pathology, 2014
SummaryDowny mildew of sunflower is caused by Plasmopara halstedii (Farlow) Berlese & de Toni. Pl... more SummaryDowny mildew of sunflower is caused by Plasmopara halstedii (Farlow) Berlese & de Toni. Plasmopara halstedii is an obligate biotrophic oomycete pathogen that attacks annual Helianthus species and cultivated sunflower, Helianthus annuus. Depending on the sunflower developmental stage at which infection occurs, the characteristic symptoms range from young seedling death, plant dwarfing, leaf bleaching and sporulation to the production of infertile flowers. Downy mildew attacks can have a great economic impact on sunflower crops, and several Pl resistance genes are present in cultivars to protect them against the disease. Nevertheless, some of these resistances have been overcome by the occurrence of novel isolates of the pathogen showing increased virulence. A better characterization of P. halstedii infection and dissemination mechanisms, and the identification of the molecular basis of the interaction with sunflower, is a prerequisite to efficiently fight this pathogen. This r...
Inheritance of 'Hullability' in Sunflowers (Helianthus annuus L.)
Plant Breeding, Aug 1, 1994
Improvement of the feed value of sunflower seedmeal by hulling achenes before crushing is of econ... more Improvement of the feed value of sunflower seedmeal by hulling achenes before crushing is of economic importance and varieties with good ‘hullability’ (ease of hulling) would be economically significant. Knowledge of the genetics of this characteristic is therefore necessary. Studies of heritability were made on a factorial cross of six female and six restorer lines. Hullability was measured as the ratio of hull removed by a laboratory huller against the total quantity of hull in the achene. The genotypes studied showed a wide range of hullabilities. There were considerable environmental effects but only small interactions; correlations between results in different locations were significant. Additive genetic effects predominated, although there were some interactions between parental lines. Narrow‐sense heritabilities were 0.73–0.85 for genotype means, 0.52 when calculated from individual plants, and 0.36–0.76 from parent‐progeny regressions. Early selection based on progeny means or a combination of individual and progeny values would appear to be the best method of breeding for improved hullability of sunflower achenes.
Euphytica, 1994
To study the genetic control of hullability in sunflower (Helianthus annuus L.), 36 hybrids, prod... more To study the genetic control of hullability in sunflower (Helianthus annuus L.), 36 hybrids, produced by a factorial cross of six male sterile and six restorer lines, were evaluated in two locations in Spain and one in France. Hullability was calculated as the ratio of the quantity of hull removed by a mechanical huller compared with total hull content. In dry conditions in Spain, hullability was twice (83 .1%) that observed in France (41 .5%). In all locations, male, female and interaction effects were significant. Estimates of narrow sense heritability varied between 0 .78 and 0.82, values similar to those for other seed characters such as oil content. There were positive genetic and phenotypic correlations between hullability and 1000 seed weight (means 0 .81 and 0.74, respectively) but negative correlations with seed oil content (-0 .73 and-0 .68, respectively). It is concluded that selection in early segregating generations of crosses involving good hulling material needs a specific strategy in order to maintain reasonable levels of oil and protein contents in the seed of the selected genotypes .
Variation of hullability and other seed characteristics among sunflower lines and hybrids
Euphytica, 1996
The hullabilities of 40 inbred lines (20 male sterility maintainers and 20 male fertility restore... more The hullabilities of 40 inbred lines (20 male sterility maintainers and 20 male fertility restorers) and 36 hybrids were studied in several environments in France. Thousand seed weight, oil and hull contents and the quantity of hulls remaining with the kernel after hulling were also measured. Principal component analyses and a hierarchical clustering method were used to described the variation of both inbreds and hybrids. Hullability varied from 11 to 66% for inbreds and 16 to 60% for hybrids. This variation is sufficient to permit breeding programmes for this character. Hullability is correlated positively with hull content (r=0.35* to 0.69*) but negatively with oil content (r=-0.34*to-0.71**). Large seeds generally hull better than small seed (r=0.21ns to -0.66**). The value of the different classes of genotypes is discussed. Inbreds and hybrids producing achenes with a quite small hull content, a high oil content but a good hullability are the most promising for improvement of the quality of sunflower seed meal. Such genotypes are rare so that a recurrent selection programme is recommended to increase the frequency of favorable genes.
La carte génétique du tournesol : le programme CARTISOL
HAL (Le Centre pour la Communication Scientifique Directe), 1994
A l'heure du sequencage du genome d'Arabidopsis (si important pour le Golza), ou en est l... more A l'heure du sequencage du genome d'Arabidopsis (si important pour le Golza), ou en est l'etablissement de la carte genetique du tournesol et la recherche des marqueurs moleculaires de resistance aux maladies, utilisables en selection?
Assessment of inter- and intra-inbred line variability in sunflower (Helianthus annuus) by RFLPs
Genome, Oct 1, 1995
The restriction fragment length polymorphism (RFLP) between 26 sunflower inbred lines was evaluat... more The restriction fragment length polymorphism (RFLP) between 26 sunflower inbred lines was evaluated with 81 probe–enzyme combinations involving 51 cDNA clones and 4 restriction enzymes (HindIII, EcoRI, EcoRV, and BglII). An average of 4.6 fragments and 4.9 profiles was detected per probe–enzyme combination, across all inbred lines. The RFLPs revealed were characterized by a high percentage (>70%) of multifragment profiles. Nei's average gene diversity was calculated to measure the genetic variability within cultivated sunflower; the average gene diversity computed with 81 probe–enzyme combinations was 0.59. The relationships between the 26 sunflower inbred lines were analysed by estimates of Nei's F index, which ranged from 0.50 to 0.91, as well as Nei's genetic distance, d, which varied from 0.05 to 0.41. A UPGMA (unweighted pair-group arithmetic average clustering) dendrogram was constructed using the genetic distance matrix; likewise, a principal component analysis was performed using the F matrix. The results obtained from the two clustering analyses allowed the separation of maintainer lines (females) from restorer lines (males). After partitioning the 26 lines into a pool of maintainer lines and a pool of restorer lines, the estimation of gene differentiations showed that the absolute difference (Dm) between females and males was only about 5%. Intraline variability was also examined in 4 sunflower inbred lines, using 30 probe–enzyme combinations. Heterogeneity at varying levels was detected in 3 of the 4 lines studied. The RFLPs detected by this set of selected clones in the 26 inbred lines suggests that RFLPs could be very useful descriptors for sunflower inbred line and variety studies.Key words: RFLPs, sunflower, inbred lines, genetic diversity.
HAL (Le Centre pour la Communication Scientifique Directe), 1989
— L'évolution de l'humidité du capitule et des graines de 25 variétés de tournesol (Heliant... more — L'évolution de l'humidité du capitule et des graines de 25 variétés de tournesol (Helianthus annuus L.), de la teneur en huile de 13 d'entre elles et du poids sec de 100 grains, pour 10 d'entre elles, ont été suivis de la floraison jusqu'à la maturité complète. L'humidité des graines diminue régulièrement au cours des 7 semaines d'étude à des vitesses différentes suivant les variétés. L'humidité du capitule ne varie pas pendant les 6 premières semaines après la floraison (70 à 80% d'eau), puis décroît de façon plus ou moins importante suivant les variétés. Un certain nombre de corrélations entre différents caractères et l'humidité au 2 septembre sont établies. Le contenu maximal en huile varie, suivant les variétés, de 44 à 52% du poids sec du grain. Il est élaboré, en moyenne, dans les 40 premiers jours après la floraison, la matière sèche du grain l'étant dans les 45 premiers jours après la floraison. Les vitesses d'évolution des teneurs en huile et en matière sèche varient en fonction des génotypes. dessèchementmatière sècheteneur en huile-maturité physiologique Summary — Changes in characteristics of sunflower seed and capitula during ripening. Changes in the humidity of capitula and seed of 25 sunflower (Helianthus annuus L.) varieties were followed from flowering to maturity, the oil content evolution was studied for 13 varieties and the 100 grain weight evolution for 10. The water content of seeds diminished regularly during the 7 weeks of the study, with significant varietal rate differences. The capitulum humidity did not vary during the six first weeks after flowering (70 to 80°/) but then was reduced to a variable extent according to variety. Correlation between different characters and humidity on 02109187 were established. The maximum oil content of the seed varied between varieties from 44 to 52°/ of dry weight. It was generaly produced during the 40 days after flowering, comparable with the dry weight, maximum 45 days after flowering days. The rates of increase of both these characteristics varied according to genotype.
The genetic control in sunflower
HAL (Le Centre pour la Communication Scientifique Directe), Dec 3, 1991
Attaque de Sclerotinia sclerotiorum sur bourgeon terminal du tournesol (Helianthus annuus). Symptômes épidémiologie et résistance
HAL (Le Centre pour la Communication Scientifique Directe), Jul 28, 1993
La selection du tournesol en France : l'age adulte
HAL (Le Centre pour la Communication Scientifique Directe), 1990
Helianthus
Springer eBooks, Sep 24, 2010
ABSTRACT Helianthus annuus the sunflower, originates from North America, where about 40 species b... more ABSTRACT Helianthus annuus the sunflower, originates from North America, where about 40 species belonging to the same genus grow wild. Ever since modern breeding programs started in the 1960s to develop hybrid varieties, wild species have been found to be useful sources of agronomic characters. Annual species with the same chromosome number as sunflower have provided cytoplasmic male sterility, restorer, and downy mildew resistance genes. Modern research addresses the possibility of introducing characters from hexaploid, perennial Helianthus species.
The use of isozyme polymorphism for identification of sunflower (Helianthus annuus) inbred lines
HAL (Le Centre pour la Communication Scientifique Directe), 1992
Le pollen, facteur d'attraction des pollinisateurs vers le tournesol (Helianthus annuus L.)
International audienc
Les varietes de tournesol cultivees actuellement ont un rendement en graines moyen de 153% des pr... more Les varietes de tournesol cultivees actuellement ont un rendement en graines moyen de 153% des premiers hybrides des annees 1970 ; le gain potentiel en rendement de plus de 1% par an se maintient. Il y a egalement eu un gain de teneur en huile d'environ 1.5 points, par rapport aux 20 ans precedents. Le genre Helianthus etant forme de 50 especes, dont le tournesol sauvage et d'autres especes annuelles qui se croisent facilement avec les genotypes cultivees, certaines des ressources genetiques cultivees peuvent etre des introgressions volontaires ou non. Les gains en rendement, quantitatifs et polygeniques sont probablement issus de tournesol cultive jusqu'a present, tandis que des changements qualitatifs viennent des especes sauvages, les plus importants etant la sterilite mâle cytoplasmique, la restauration, la ramification et des resistances au mildiou et a l'orobanche. Les possibles apports futurs de ces ressources au progres varietal sont discutes.
The sunflower diseases for which publications are most frequent are Sclerotinia, downy mildew, br... more The sunflower diseases for which publications are most frequent are Sclerotinia, downy mildew, broomrape and Phomopsis. Resistance breeding has so far been concerned with either major gene resistance (downy mildew, broomrape) or quantitative resistance (Sclerotinia, Phomopsis). With major genes, resistance has been complete but not durable. Although new genes are regularly found, they are quite rapidly overcome. For quantitative resistance, although progress has been quite rapid in the case of Phomopsis, it has been slow for Sclerotinia and some research has concerned the possibility of genetic transformation. For efficient disease control in the future, it is proposed that, when available, vertical and horizontal resistances should be combined and if this is not the case, marker-assisted selection should be used to combine QTLs with different and additive defence mechanisms.
MARKER OF RESISTANCE TO $i(SCLEROTINIA SCLEROTIORUM)
OCL, 2016
This article discusses changes in sunflower breeding objectives since the introduction of hybrid ... more This article discusses changes in sunflower breeding objectives since the introduction of hybrid varieties 50 years ago. After a reminder of the importance of some early programmes, Canadian in particular, the present situation for each breeding objective is compared with those encountered earlier. Breeding for yield has changed from maximum possible yield under intensive agriculture to yield with resistance to abiotic stresses, moderate droughts and shallow soils in particular, helped by collaboration with agronomists to produce crop models. Breeding for oil has changed from quantity to quality and the value of seed meal is again becoming economically important. Necessary disease resistances vary with agronomic practises and selection pressure on pathogens according to varietal genetics. The possibilities of new types of sunflower are also discussed. Advances in genomics will change breeding procedures, but with rapidly changing molecular techniques, international collaboration is particularly important.
Helianthus
Wild Crop Relatives: Genomic and Breeding Resources, 2010
ABSTRACT Helianthus annuus the sunflower, originates from North America, where about 40 species b... more ABSTRACT Helianthus annuus the sunflower, originates from North America, where about 40 species belonging to the same genus grow wild. Ever since modern breeding programs started in the 1960s to develop hybrid varieties, wild species have been found to be useful sources of agronomic characters. Annual species with the same chromosome number as sunflower have provided cytoplasmic male sterility, restorer, and downy mildew resistance genes. Modern research addresses the possibility of introducing characters from hexaploid, perennial Helianthus species.
Molecular Plant Pathology, 2014
SummaryDowny mildew of sunflower is caused by Plasmopara halstedii (Farlow) Berlese & de Toni. Pl... more SummaryDowny mildew of sunflower is caused by Plasmopara halstedii (Farlow) Berlese & de Toni. Plasmopara halstedii is an obligate biotrophic oomycete pathogen that attacks annual Helianthus species and cultivated sunflower, Helianthus annuus. Depending on the sunflower developmental stage at which infection occurs, the characteristic symptoms range from young seedling death, plant dwarfing, leaf bleaching and sporulation to the production of infertile flowers. Downy mildew attacks can have a great economic impact on sunflower crops, and several Pl resistance genes are present in cultivars to protect them against the disease. Nevertheless, some of these resistances have been overcome by the occurrence of novel isolates of the pathogen showing increased virulence. A better characterization of P. halstedii infection and dissemination mechanisms, and the identification of the molecular basis of the interaction with sunflower, is a prerequisite to efficiently fight this pathogen. This r...