Comportement de quatre variétés de blé tendre vis-à-vis de la fusariose de l'épi causée par Fusarium roseum var. culmorum (Schwabe) Sn. et H

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Mapping of quantitative trait loci for field resistance to Fusarium head blight in an European winter wheat

53 ref.International audienceFusarium head blight (FHB) caused by Fusarium culmorum is an economically important disease of wheat that may cause serious yield and quality losses under favorable climate conditions. The development of disease-resistant cultivars is the most effective control strategy. Worldwide, there is heavy reliance on the resistance pool originating from Asian wheats, but excellent field resistance has also been observed among European winter wheats. The objective of this study was to map and characterize quantitative traits loci (QTL) of resistance to FHB among European winter wheats. A population of 194 recombinant inbred lines (RILs) was genotyped from a cross between two winter wheats Renan (resistant)/Recital (susceptible) with microsatellites, AFLP and RFLP markers. RILs were assessed under field conditions For 3 years in one location. Nine QTLs were detected, and together they explained 30-45% of the variance, depending on the year. Three of the QTLs were stable over the 3 years. One stable QTL, QFhs.inra.2b, was mapped to chromosome 2B and two QTLs QFhs.inra.5a2 and QFhs.inra.5a3, to chromosome 5A; each of these QTLs explained 6.9-18.6% of the variance. Other QTLs were identified on chromosome 2A, 3A, 3B, 5D, and 6D, but these had a smaller effect on FHB resistance. One of the two QTLs on chromosome 5A was linked to gene B1 controlling the presence of awns. Overlapping QTLs for FHB resistance were those for plant height or/and flowering time. Our results confirm that wheat chromosomes 2A, 3A, 3B, and 5A carry FHB resistance genes, and new resistance factors were identified on chromosome arms 2BS and 5AL. Markers flanking these QTLs should be useful tools for combining the resistance to FHB of Asian and European wheats to increase the resistance level of cultivars

Quelle(s) sélection(s) du blé tendre pour l'agriculture biologique ? Résultats et perspectives d'un comparatif avec les performances variétales en conduite "faibles intrants"

La sélection de variétés adaptées aux conditions variables de l’agriculture biologique est l’une des solutions possibles pour augmenter les rendements et maintenir, voire améliorer, la qualité du blé tendre cultivé selon ce mode de culture. Entre 2004 et 2011, le groupe d’innovation variétale « blé tendre » du département DGAP de l’INRA a mis en place un dispositif expérimental dans trois régions aux conditions pédoclimatiques variées intégrant l’évaluation de génotypes diversifiés en conduite « faibles intrants » (FI) et en agriculture biologique (AB). La comparaison des 17 couples d’essais FI / AB retenus montre l’intérêt d’une sélection indirecte par la conduite « faibles intrants » pour identifier des génotypes propices à l’AB pour différents caractères dont le rendement et la teneur en protéines des grains mais aussi pour caractériser les génotypes « GPD + » (positive Grain Protein Deviation) qui valoriseraient mieux l’azote disponible. L’aptitude à la panification, très souvent altérée et plus instable en AB, nécessite toutefois d’évaluer les génotypes sélectionnés dans les conditions de l’AB, au moins dans les dernières années de sélection

Is low-input management system a good selection environment to screen winter wheat genotypes adapted to organic farming?

The move toward resilient and productive agriculture requires, among other innovations, the design of new sustainable farming systems in which the variety plays a main role. Plant breeding strategies adapted to organic farming conditions have to deal with limiting factors. Whereas in north-west France, it is known that trials carried out under high-input management do not give a good prediction of genotype performance in organic conditions, less is known about the relative stability of wheat genotypes between low-input (LI) and organic cropping systems. A retrospective analysis of 34 winter wheat trials conducted from 2004 to 2011 was performed to determine whether data obtained on genotypes grown under LI conditions can be used to predict genotype performance in organic (ORG) target conditions. Every year, ORG and LI (no fungicide or growth regulators, N balance sheet-60 kgN/ha, weed control with herbicides) trials including 25-30 genotypes describing a large range of genetic diversity were sown in three different agro-climatic regions across north-west France. Genotype performance in ORG management system was reduced from 25 to 40 % for yield and from 10 to 22 % for grain protein content. Estimates of genotypic values appeared to be more precise under LI than ORG conditions. Because of high genetic correlations between LI and ORG conditions, the relative efficiency of indirect selection from LI to ORG conditions was approximately 1. Spearman's rank correlations were high (Rs = 0.54-0.92) and genotype rank inversions generally had a minor extent. However, in 2005 and 2010, almost 50 % of the lines had to be retained in LI to keep 80 % of the top 20 % of genotypes in organic conditions. Compared with previous results from high-input conditions, LI management provided a better prediction of genotype performance under ORG conditions but crossover genotype x management interactions could be observed between both systems. Overall, combining information provided from both LI and ORG crop management systems appears to be a good process for building efficient and adapted breeding schemes for ORG farming conditions

Low Incidence Of Fusarium In Organic Farming On Bread Wheat Grains Over A 13-Year Period

Organic farming has been questioned about its ability to manage Fusarium infestation compared with conventional farming. In this study, we monitored, over a 13-year period in several sites in France, the fungal incidence of four genera of fungi on bread wheat grains from organic farming. We collected samples immediately after harvest in conditions of natural contamination on a list of winter wheat varieties from 2006 to 2018 in several sites in France. From each sample, 100 kernels were surface disinfected, plated on potato dextrose agar, and colonies were identified at the genus level, and at the species level for Fusarium graminearum. The fungal incidence observed on kernels over the period was on average 88 ± 16% (i.e. mean ± standard-deviation). Kernels were mainly infected by fungal species of the genus Alternaria (71 ± 25%), while the incidence of Fusarium graminearum is usually very low in our context (1 ± 2%), with the exception of year 2008 (49 ± 12% and 17 ± 9%, respectively in the two sites studied), which is confirmed by the highly significant effect of the year and the ‘year × site’ interaction. To conclude, in our study, Fusarium graminearum appeared not to be a major concern for wheat production in organic farming systems

Incidence of four genera of fungi in organic and low-input farming conditions in/on the grain of bread wheat over a 13-year period in France

International audienceBread wheat can be infected and/or contaminated by several genera of mycotoxin-producing fungi. In the European Union, several mycotoxins are subject to defined limits for human consumption. Speculation has arisen about the potential higher contamination level of mycotoxins produced by Fusarium species in organic compared to conventional production systems. So far, many studies have focused on the level of mycotoxins, highlighting comparable levels in organic and conventional farming. In this long-term study, we monitored, each year over a 13-year period in several sites in France and for a set of bread wheat genotypes, the incidence of four fungal genera on bread wheat grains from both conventional low-input and organic farming. During this long period of monitoring, we used the same morphological characterization of fungal colonies. The results obtained highlighted two general trends. First, the incidence of the genus Fusarium in grains was generally lower than or equal to 1% in more than 60% of “year × site” combinations, both in low-input and organic farming conditions. In contrast, the genus Alternaria was dominant in the vast majority of combinations. Second, the main explanatory factors of the incidence of fungus on grains, independently of the genus and the farming conditions, were the year and the “year × site” interaction, suggesting the dominant influence of the environmental conditions of the year and the site on the relative development of the fungal genera in/on grains. According to these results, organic or low-input production of bread wheat does not represent a significant risk for the development of Fusarium head blight in France

A study of genetic progress due to selection reveals a negative effect of climate change on bread wheat yield in France

International audienceIn France, a stagnation of bread wheat yield has been observed since the middle of the 1990s, and the possibility of a decline in breeding progress has been questionned. To investigate this hypothesis, we have considered 2 independent long time series of yield data: one corresponding to the registration trials conducted in France from 1976 to 2010, and the other corresponding to trials from the INRA bread wheat breeding program along the 1970-2010 period. These raw data related to potential bread wheat yield in France, exhibited the same trend to stagnation as observed on national yield in the farms. However, after correction of the "year" effects, the corrected yields appeared to have increased regularly from the 1970s up to now, with quite a high rate in intensive conditions (from 0.065 t ha(-1) yr(-1) to 0.137 t ha(-1) yr(-1)). This linear trend for genetic progress was even higher without fungicide (from 0.097 t ha(-1) yr(-1) to 0.158 t ha(-1) yr(-1)), which could indicate that breeding efforts for productivity and for resistance to diseases tended to have additive results. The corrected yields also enabled us to point out a marked degradation of the agro-climatic potential of the different years. As our registration and breeding trials were as free as possible from agronomic limiting factors, it appeared that climatic factors constituted the main explanation to this degradation. Thus, our study demonstrated that since the end of the 1980s, genetic progress has been partly or totally counterbalanced by the adverse effects of climate change. (C) 2012 Elsevier B.V. All rights reserved