résistance / Fusarium culmoruml blé / sélection récurrente / sélection précoce / héritabilité Summary — Heritability and recurrent selection for resistance to Fusarium head blight in winter wheat. Fifty-six S 1 families and their S 2 progeny from a winter wheat population with genic male sterility were evaluated for reaction to Fusarium head blight. Families were tested in the field using artificial inoculation. Tests were repeated over 2 years for S 1 families. Disease severity was scored on spikes and seeds. The effect of the disease on yield and thousand grain weight was measured using uninoculated control plots. A significant correlation was found between disease severity and thousand grain weight decrease (table I). Despite significant year x genotype interaction (table II), correlation coefficients between the 2 years for disease evaluation on S 1 families were high (r=0.79 for severity in seeds). Broad sense heritabilities were from 0.8 to 0.9 (table III) and justify early selection for Fusarium resistance in the population. Because of low S 1 -S 2 heritability (table V), using sibs of tested plants instead of offspring is suggested for the recurrent selection scheme.

The inheritance of avenin components, the prolamins (or alcohol soluble proteins) of Avena, is studied by means of gel electrophoresis. Avenin is composed of rather similar proteins which appear as a polymorphic group from a biochemical point of view. After a first preliminary investigation it showed a surprisingly high interspecific variability. The average number of its constituents increases with the ploidy level but it still is much lower than that of wheat gliadin.The avenin electrophoretic patterns of 47 samples (F4, F5 or F6 seeds) resulting from 3 hexaploid crosses are compared with the parental patterns. Four kinds of inheritance are observed. Roughly 50% of progeny profiles are identical to those of one of the parents. They are composed occasionally of partial sections of parental patterns. Complete additiveness occurs rather seldom. However, in one of the crosses a significant number of progeny samples show a band, one of the very slow moving constituents, which was not present in either of the parents.The study of avenin in F1 seeds, arising from reciprocal crosses between two homozygous parent plants, shows a significant effect of maternal gene dose in the triploid endosperm.Because of both the variability and the relatively small number of avenin constituents, these results show that typical endosperm proteins such as oat prolamin constitute a useful tool for phylogenetic studies of the genus Avena.

Fusarium roseum var culmorum / blé / rendement / cultivar Summary — Relationship between head blight symptoms of Fusarium roseum var culmorum and yield losses in wheat. Four winter wheat cultivars were inoculated in field tests by Fusarium roseum var culmorum over a 4-yr period. Several spore concentrations of the inoculum were used each year. The severity of the disease was evaluated using the number of damaged spikelets at the early dough growth stage and the percentage of visually infected seeds at harvest. Yield and 1 000 grain weight losses were measured with reference to an uninoculated control. A significant correlation was found between the number of damaged spikelets and the number of visually infected seeds together with an effect of the variety and the year. On a linear basis, because of a weak year effect, the decrease in 1 000 grain weight is better predicted using the number of visually infected seeds than the number of damaged spikelets. There is a trend for non-linear response curves for 2 varieties. The use of field evaluation of severity of the disease and tolerance of varieties are discussed.Fusarium roseum var culmorum / wheat / yield / cultivar

— Disease progress of Pseudocercosporella herpotrichoides in mixed stands of winter wheat cultivars. Epidemic development of Pseudocercosporella herpotrichoides in pure stands of a susceptible variety and a variety with the Pch1 resistance gene, and in their (1:1) mixture was examined in six situations differing for location, fungicide protection or contamination. At growth stade 32, no significant difference was found between the disease level in mixtures and the mean of the disease levels of the mixture components in pure stand. At booting and milky ripe stages, plants sampled in the mixtures were separated according to the variety. No significant difference was found between the disease level in pure stand and in mixed stand either for the susceptible variety nor for the Pch1 one. Triticum aestivum / Pseudocercosporella herpotrichoides / cultivars / variety mixture Résumé — Le développement du piétin-verse sur une variété sensible, une variété possédant le gène de résistance Pch1 et leur association à parts égales est étudié dans six situations qui diffèrent par le lieu, la protection fongicide ou le mode de contamination. Aucune différence de niveau de maladie n'est observée entre l'association et la moyenne des deux composants au stade deux nœuds. Aux stades gonflement et grain laiteux, les variétés sont identifiées dans l'association et notées séparément. Le niveau de maladie en culture pure n'est pas significativement différent de celui de l'association ni pour la variété sensible, ni pour la variété Pch1. Triticum aestivum / Pseudocercosporella herpotrichoides / variété résistante / association variétale