Resistance to eyespot (Pseudocercosporella herpotricoides) and distribution of biochemical markers in hexaploid lines derived from double cross (Triticum turgidum x Aegilops ventricosa) x T. aestivum

There are not good intraspecific sources of resistance to the eyespot disea se of wheat, aaused by Cercosporella herpotrichoides Fvon . The -ínterspecifia transfer of genes for resistanoe from Aegitops ventricosa into hexaploid wheat has been only partially achieved, because the degree of resistanoe attained is not as high as that of the donor. We report here on the transfer of resistanoe in a double oross (Triticum turgidum var. rubroatrwv H-1-1 x Ae.ventricosa AP-D x T.aestivum cv. Almatense H-10-15. The high level of resistanoe in a high proportion of the lines strongly suggests a simple genetic control for this oharacter (possibly by one major gene). The gene(s) responsible for resistanoe in the selected lines must be associa ted with the D genome of Aegilops ventricosa on the basis of a detailed study of the distribution of biochemioal markers in the H-93 lines. These results do not exelude that genes with similar effeets might be looated in the M° genome

Eyespot resistance gene Pch-1 from Aegilops ventricosa is associated with a different chromosome in wheat line H-93-70 than the resistance factor in "Roazon" wheat

The hexaploid wheat line H-93-70 carries a gene (Pch-1) that has been transferred from the wild grass Aegilops ventricosa and confers a high degree of resistance to eyespot diesease, caused by the fungus Pseudocercosporella herpotrichoides. Crosses of the resistant line H-93-70 with the susceptible wheat Pané 247 and with a 7D/7Ag wheat/Agropyron substitution line were carried out and F2 kernels were obtained. The kernels were cut transversally and the halves carrying the embryos were used for the resistance test, while the distal halves were used for genetic typing. Biochemical markers were used to discriminate whether the transferred Pch-1 gene was located in chromosome 7D, as is the case for a resistance factor present in Roazon wheat. In the crosses involving Pané 247, resistance was not associated with the 7D locus Pln, which determines sterol ester pattern (dominant allele in H-93-70). In the crosses with the 7D/7Ag substitution line, resistance was neither associated with protein NGE-11 (7D marker), nor alternatively inherited with respect to protein C-7 (7Ag marker). It is concluded that gene Pch-1 represents a different locus and is not an allele of the resistance factor in Roazon whea

Eyespot resistance gene Pch-1 in H-93 wheat lines. Evidence of linkage to markers of chromosome group 7 and resolution from the endopeptídase locus Ep-Dlb

Gene Pch1, which confers resistance to eyespot disease (Pseudocercosporella herpotrichoides Fron), has been located on chromosome 7D in the H-93 wheat-Aegilops ventricosa transfer lines using isozyme markers and DNA probes corresponding to group 7 chromosomes. Previous experiments had failed to ascertain this location. The lack of segregation of the resistance trait in progeny from reciprocal crosses between lines H-93-70 and VPM1 indicates that their respective resistance factors are allelic. Line H-93-51 carries the endopeptidase allele Ep-D1b but is susceptible to eyespot, which indicates that resistance to eyespot is not a product of the Ep-D locus, as had been proposed in a previous hypohesi

Transfer of a major dominant gene for resistance to eyespot disease from a wild grass to hexaploid wheat

Eyespot disease, caused by the fungus Pseudocercosporella herpotrichoides, is responsible for considerable lodging and reductions of yield in extensive areas of wheat cultivation in North and South America, Europe, New Zealand, Australia and Africa1. The level of resistance of wheat cultivars is too low, even among the less susceptible ones (that is, Cappelle Desprez and Cerco) and no genes for resistance have to date been characterized in any species. Sprague2 found a high level of resistance to this disease in the wild grass Aegilops ventricosa and several workers have attempted its transfer to cultivated wheat with only partial success3−5. We report here a major dominant gene for resistance, which has been transferred from tetraploid Ae. ventricosa (genomes DvDvMvMv) to hexaploid wheat, Triticum aestivum (AABBDD), using tetraploid wheat, Triticum turgidum (AABB), as a 'bridge' species

Biochemical markers associated with two Mv chromosomes from Aegilops ventricosa in wheat-Aegilops addition lines

The distribution of three biochemical markers, U-1, CM-4 and Aphv-a, -b, among wheat-Aegilops addition lines carrying Mv chromosomes from Aegilops ventricosa (genomes DvMv) has been investigated. Addition lines which had been previously grouped together on the basis of common non-biochemical characters carried marker U-1, a protein component from the 2M urea extract. The added chromosome, in the appropriate genetic background, seems to confer a high level of resistance to the eyespot disease, caused by the fungus Cercosporella herpotrichoides. The other two markers were concomitantly associated with another similarly formed group of addition lines. Both CM-4, a protein component from the chloroform:methanol extract, and Aphv-a, -b, alkaline phosphate isozymes, have been previously shown to be associated with homoeologous chromosome group 4, which suggests that the added chromosome in the second group of addition lines is 4Mv

Biochemical and cytological characterization of wheat/Aegilops ventricosa addition and transfer lines carrying chromosome 4MV

The gene encoding a variant of alcohol dehydrogenase, Adh-, has been found to be associated with the chromosome of the Mv genome which is present in type 9 wheat/Aegilops ventricosa addition line, to which the genes for protein CM-4 and for a phosphatase variant, Aph-v, had been previously assigned. Transfer line H-93-33, which has 42 chromosomes and has been derived from the cross (Triticum turgidum x Ae. ventricosa) x T. aestivum, carries genes encoding all three biochemical markers. Linkage between these genes has been demonstrated by analysis of individual kernels of the F2 (H-93-33 x T. aestivum cv. Almatense H-10-15). A study of the hybrids of line H-93-33 with T. aestivum H-10-15 and with the 4DS ditelosomic line has confirmed that, as suspected, the linkage group corresponds to chromosome 4Mv from Ae. ventricosa. Additionally, it has been found that the previously reported resistance of line H-93-33 to powdery mildew (Erysiphe graminis) is also linked to the biochemical markers; this indicates that either the gene responsible for it is different from that in lines H-93-8 and H-93-35, or that a translocation between two different Mv chromosomes has occurred in line H-93-33

Resistance to the cereal cyst nematode (Heterodera avenae) transferred from the wild grass Aegilops ventricosa to hexaploid wheat by a "stepping-stone" procedure

Transfer of resistance toHeterodera avenae, the cereal cyst nematode (CCN), by a stepping-stoneprocedure from the wild grassAegilops ventricosa to hexaploid wheat has been demonstrated. The number of nematodes per plant was lower, and reached a plateau much earlier, in the resistant introgression line H93-8 (1–2 nematodes per plant) than in the recipient H10-15 wheat (14–16 nematodes per plant). Necrosis (hypersensitive reaction) near the nematode, little cell fusion, and few, often degraded syncytia were observed in infested H93-8 roots, while abundant, well-formed syncytia were present in the susceptible H10-15 wheat. Line H93-8 was highly resistant to the two Spanish populations tested, as well as the four French races (Fr1-Fr4), and the British pathotype Hall, but was susceptible to the Swedish pathotypes HgI and HgIII. Resistance was inherited as though determined by a single quasi-dominant factor in the F2 generations resulting from crosses of H93-8 with H10-15 and with Loros, a resistant wheat carrying the geneCre1 (syn.Ccn1). The resistance gene in H93-8 (Cre2 orCcn2) is not allelic with respect to that in Loros. RFLPs and other markers, together with the cytogenetical evidence, indicate that theCre2 gene has been integrated into a wheat chromosome without affecting its meiotic pairing ability. Introduction ofCre2 by backcrossing into a commercial wheat backgroud increases grain yield when under challenge by the nematode and is not detrimental in the absence of infestation

Méthodologie de l'amélioration du blé tendre (Triticum aestivum L). II. Étude et analyse de deux premiers cycles de sélection récurrente

Pour étudier l'intérêt de la sélection récurrente sur une espèce autogame stricte, le blé tendre, un schéma d'amélioration en population est appliqué à une population à 16 parents. Il est basé sur la succession de cycles courts de 3 générations, chacun comprenant 2 générations de sélection et 1 génération d'intercroisement des génotypes sélectionnés. La sélection au cours des générations d'autofécondation est réalisée à l'aide d'index de sélection phénotypique combinant de nombreux caractères pour l'amélioration globale du blé. L'étude des 2 premiers cycles est réalisée en comparant la population finale PA 1 à la population initiale PA0 ou à l'ensemble des parents de départ de PA0. Elle montre l'efficacité d'un tel processus en mettant en évidence en particulier une augmentation des valeurs moyennes, après les 2 cycles, pour la plupart des caractères sélectionnés. Par ailleurs, la variabilité intrapopulation, mesurée à partir des variances phénotypiques (et génétiques dans PA1), reste sensiblement au niveau initial, sauf pour les caractères fortement sélectionnés pour lesquels elle tend à diminuer. Ce bilan est discuté, notamment pour améliorer le mode d'utilisation d'un schéma de sélection récurrente dans une stratégie générale d'amélioration du blé tendre.Breeding methodology in soft wheat (Triticum aestivum L). II. Study and analysis of two cycles of a recurrent selection scheme. In order to study recurrent selection effects on soft wheat, a strictly self-fertilizing species, a recurrent breeding scheme was applied to a 16-parent population. It was based on a 3-generation cycle including 2 generations of selection and 1 intercrossing generation of the best genotypes. Selection based on selfing regime was performed with phenotypic indices which combine the main characters introduced in general wheat breeding. The analysis of the 2 first cycles was based on the comparison of the final population (PA 1) with the initial population (PA0) or with the 16-parent group introduced in PA0. It shows the efficiency of such a scheme with an increase in mean level for most characters studied. Moreover, the intrapopulation variability estimated by phenotypic variances (and genetic variances for PA1) remained at the same level except for the characters that were intensively selected. These evaluations provide a basis for discussion on a better way to insert and apply recurrent selection in a wheat breeding strategy

Abnormalities in the male developmental programme of winter wheat induced by climatic stress at meiosis

From the onset of meiosis, wheat plants, cv Moulin and Pernel, were subjected to climatic stress for 7 days in a growth chamber. The stress conditions (11 μmol.m-2.s -1 photosynthetic photon flux density, 1.5/8 °C night/day, 12.5 h photoperiod) were chosen so that the stress affected the grain set in a similar way to low radiation, possibly associated with chilling in the field. Control plants received 203 μmol.m-2.s-1 photosynthetic photon flux density, 15/18 °C temperatures and 16 h photoperiod. In stressed plants, the grain set was reduced due to poor fertilization, as shown by the absence of development of endosperms from the embryo sacs. Male development was affected: anthers were frequently small, curved or shrivelled, and did not dehisce. Pollen release was limited and the pollen load on the stigma was low. Pollen viability (fluorochromatic reaction) was altered, but pollen grains were normally trinuclear at anthesis. Female fertility was unaffected. Both varieties showed the same alterations.Anomalies dans le programme mâle du blé d'hiver induites par un stress climatique à la méiose. Du blé (variétés Moulin et Pernel) a été soumis à un stress climatique durant 7 jours à partir du début de la méiose, en chambre de culture. Les conditions de stress (densité de flux de photons de 11 μmol.m-2.s-1, 1,5/8 °C nuit/jour, photopériode de 12 h 30) ont été choisies de façon à ce que ce stress ait les mêmes effets sur la nouaison qu'un éclairement faible, éventuellement accompagné d'une température basse, au champ. Les plantes témoins étaient soumises à une densité de flux de photons de 203 μmol.m-2.s-1, des températures de 15/18 °C et une photopériode de 16 heures. Chez les plantes stressées, la nouaison a été réduite suite à un déficit de fécondation, mis en évidence par l'absence de développement d'albumen dans les sacs embryonnaires. Le développement mâle a été affecté : de nombreuses anthères étaient petites, incurvées ou recroquevillées et non déhiscentes. La libération du pollen a été réduite et la quantité de pollen disséminée sur les stigmates était faible. La viabilité du pollen (réaction fluorochromatique) a été altérée, en revanche les grains de pollen étaient normalement trinucléés lors de l'anthèse. La fertilité femelle n'a pas été affectée. Les deux variétés ont présenté les mêmes altérations

Early assessment of adult plant reaction of wheat (Triticum aestivum L) to powdery mildew (Erysiphe graminis f sp tritici) at the five-leaf seedling stage

An original procedure leading to the early prediction of adult plant reaction to powdery mildew infection at a seedling stage was defined. Seedlings of eight wheat lines were inoculated at the two- and five-leaf stages with various inocula (either clones or synthetic mildew populations) overcoming their major specific resistance genes. The mean mildew score (MMS) and the mean time for first sporulation (MTFS) proved to be strongly correlated. For each line tested, the mildew reaction of adult plants was closely predicted by that of vernalized, five-leaf seedlings. Using inoculations on five-leaf vernalized seedlings, we can predict the adult stage mildew reaction of a line, where the specific resistance should be overcome. Using this method, it is possible to study the genotypes, the specific resistance of which are still effective in the field, thus preventing assessment of their possible non-specific adult plant resistance in the field.Prédiction précoce du comportement adulte du blé (Triticum aestivum L) vis-à-vis de l'oïdium (Erysiphe graminis f sp tritici) chez de jeunes plantes au stade cinq-feuilles. Une procédure originale permettant de prévoir de façon précoce, chez de jeunes plantes de blé, la réaction au stade adulte vis-à-vis de l'infection par l'oïdium, a été définie. Les jeunes plantes de neuf lignées de blé ont été inoculées au stade deux-feuilles et au stade cinq-feuilles par des inocula divers - soit des clones, soit des populations synthétiques d'oïdium - contournant les gènes de résistance spécifique de ces lignées. Une forte corrélation a été établie entre la note moyenne d'attaque et le temps moyen d'apparition des premières sporulations. Pour chacune des lignées étudiées, le comportement adulte vis-à-vis de l'oïdium a pu être prédit avec précision par celui des jeunes plantes vernalisées, inoculées au stade cinq-feuilles. Cette procédure permet de prédire, dès le stade jeune plante, quel sera le comportement d'une lignée au stade adulte, si ses gènes de résistance spécifiques devaient être contournés. Cette méthode rend possible l'étude de génotypes dont les gènes de résistance spécifique sont toujours efficaces au champ, interdisant ainsi de ce fait l'évaluation de la résistance adulte non spécifique de ces génotypes