Exploitation des champignons mycorhiziens à arbuscules pour la protection du tournesol contre Orobanche cumana

Les plantes parasites telles que l'orobanche causent de nombreux dégâts sur les cultures et il existe peu de méthodes efficaces pour lutter contre ce fléau. L'objectif de la thèse a été de déterminer si des micro-organismes vivant en symbiose avec les plantes, les champignons mycorhiziens à arbuscules, peuvent être utilisés pour combattre les attaques d'Orobanche cumana sur le tournesol. Nous avons tout d'abord observé que la mycorhization de plants de tournesol réduit significativement leur infection par Orobanche cumana. Cet effet semble au moins en partie dû à une moindre germination des graines d'orobanche à proximité des plants mycorhizés. Nous avons ensuite montré que les champignons mycorhiziens euxmêmes produisent des inhibiteurs de la germination des graines d'orobanche. Enfin, nous avons mis au point un système in vitro permettant d'observer toutes les étapes précoces de l'infection de racines de tournesol par Orobanche cumana, en présence ou non de champignons mycorhiziens.Parasitic weeds such as broomrapes (Orobanche spp.) can cause severe damage on crop plants, and efficient and sustainable control methods are needed. The aim of our work was to determine whether symbiotic micro-organisms called arbuscular mycorrhizal fungi can be used as a biocontrol method to protect sunflower against Orobanche cumana. We first observed that mycorrhization of sunflower plants reduced significantly their infection by Orobanche cumana. We then showed that mycorrhizal sunflower root exudates induced lower Orobanche cumana seed germination than non-mycorrhizal root exudates. Moreover, we demonstrated for the first time that AM fungi alone could produce inhibitors of Orobanche seed germination. Finally, we set up a novel in vitro system in which the early stages of sunflower root infestation by Orobanche cumana can be monitored. This system could be used to investigate possible effects of mycorrhizal fungi on these different stages

Association mapping for broomrape resistance in sunflower

IntroductionSunflower breeding for resistance to the parasitic plant sunflower broomrape (Orobanche cumana Wallr.) requires the identification of novel resistance genes. In this research, we conducted a genome-wide association study (GWAS) to identify QTLs associated with broomrape resistance.MethodsThe marker-trait associations were examined across a germplasm set composed of 104 sunflower accessions. They were genotyped with a 600k AXIOM® genome-wide array and evaluated for resistance to three populations of the parasite with varying levels of virulence (races EFR, FGV, and GTK) in two environments.Results and DiscussionThe analysis of the genetic structure of the germplasm set revealed the presence of two main groups. The application of optimized treatments based on the general linear model (GLM) and the mixed linear model (MLM) allowed the detection of 14 SNP markers significantly associated with broomrape resistance. The highest number of marker-trait associations were identified on chromosome 3, clustered in two different genomic regions of this chromosome. Other associations were identified on chromosomes 5, 10, 13, and 16. Candidate genes for the main genomic regions associated with broomrape resistance were studied and discussed. Particularly, two significant SNPs on chromosome 3 associated with races EFR and FGV were found at two tightly linked SWEET sugar transporter genes. The results of this study have confirmed the role of some QTL on resistance to sunflower broomrape and have revealed new ones that may play an important role in the development of durable resistance to this parasitic weed in sunflower

Slow Solar Wind Connection Science during Solar Orbiter’s First Close Perihelion Passage

The Slow Solar Wind Connection Solar Orbiter Observing Plan (Slow Wind SOOP) was developed to utilize the extensive suite of remote-sensing and in situ instruments on board the ESA/NASA Solar Orbiter mission to answer significant outstanding questions regarding the origin and formation of the slow solar wind. The Slow Wind SOOP was designed to link remote-sensing and in situ measurements of slow wind originating at open–closed magnetic field boundaries. The SOOP ran just prior to Solar Orbiter’s first close perihelion passage during two remote-sensing windows (RSW1 and RSW2) between 2022 March 3–6 and 2022 March 17–22, while Solar Orbiter was at respective heliocentric distances of 0.55–0.51 and 0.38–0.34 au from the Sun. Coordinated observation campaigns were also conducted by Hinode and IRIS. The magnetic connectivity tool was used, along with low-latency in situ data and full-disk remote-sensing observations, to guide the target pointing of Solar Orbiter. Solar Orbiter targeted an active region complex during RSW1, the boundary of a coronal hole, and the periphery of a decayed active region during RSW2. Postobservation analysis using the magnetic connectivity tool, along with in situ measurements from MAG and SWA/PAS, showed that slow solar wind originating from two out of three of the target regions arrived at the spacecraft with velocities between ∼210 and 600 km s−1. The Slow Wind SOOP, despite presenting many challenges, was very successful, providing a blueprint for planning future observation campaigns that rely on the magnetic connectivity of Solar Orbiter

Caractérisation préliminaire de la kinésine AT5G27950 en contexte sain et infecté par le Cauliflower mosaic virus

UMR BGPI -Equipe 2 Diplôme : MasterKinesins are cellular motors playing many roles in the cell, from transport of molecules to reorganization of the cytoskeleton. Viruses use these transporters to move themselves and/or other viral products in the cell. Cauliflower mosaic virus (CaMV) forms in the cytoplasm of infected cells a "Transmission Body" (TB), a viral inclusion implicated in transmission of CaMV. Previously, it was shown that a kinesin (TBK5) of a non-host plant might be implicated in the formation of the TB. We show here that the kinesin AT5G27950 (AT5) of Arabidopsis, a CaMV host, is a functional homologue of TBK5 and is probably implicated in TB formation. We show, using transient expression assays in protoplasts, that that the fusion GFP-AT5 has properties similar to TBK5; AT5 localizes on the microtubule network and around/within the nucleus, a heat shock induces its motor domain-dependent relocalization in a single perinuclear aggregate, and AT5 colocalizes with the TB during its formation. While its natural functions remain unknown, our data suggest a role for AT5 in the generation of the TB of CaMV

Reduced germination of Orobanche cumana seeds in the presence of Arbuscular Mycorrhizal fungi or their exudates.

Broomrapes (Orobanche and Phelipanche spp) are parasitic plants responsible for important crop losses, and efficient procedures to control these pests are scarce. Biological control is one of the possible strategies to tackle these pests. Arbuscular Mycorrhizal (AM) fungi are widespread soil microorganisms that live symbiotically with the roots of most plant species, and they have already been tested on sorghum for their ability to reduce infestation by witchweeds, another kind of parasitic plants. In this work AM fungi were evaluated as potential biocontrol agents against Orobanche cumana, a broomrape species that specifically attacks sunflower. When inoculated simultaneously with O. cumana seeds, AM fungi could offer a moderate level of protection against the broomrape. Interestingly, this protection did not only rely on a reduced production of parasitic seed germination stimulants, as was proposed in previous studies. Rather, mycorrhizal root exudates had a negative impact on the germination of O. cumana induced by germination stimulants. A similar effect could be obtained with AM spore exudates, establishing the fungal origin of at least part of the active compounds. Together, our results demonstrate that AM fungi themselves can lead to a reduced rate of parasitic seed germination, in addition to possible effects mediated by the mycorrhizal plant. Combined with the other benefits of AM symbiosis, these effects make AM fungi an attractive option for biological control of O. cumana

Pollen viability restoration in a Coffea canephora P. and C. heterocalyx Stoffelen backcross. QTL identification for marker-assisted selection

DOI: 101007/s00122-002-1018-xInternational audienc

Introgression of self-compatibility from Coffea heterocalyx to the cultivated species Coffea canephora

DOI: 10.1007/s00122-002-1008-zInternational audienc

Toward a better understanding of the genetic architecture of sunflower (Helianthus annuus) resistance to the parasitic plant Orobanche cumana

Trabajo presentado en el Third Internacional Symposium on broomrape (Orobanche spp.) in Sunflower, celebrado en Córdoba (España) del 3 al 6 de junio de 2014.The plant parasite Orobanche cumana is a major threat for the sunflower crop. The emergence of new, virulent “races” during the ten past years reinforced the need to develop new approaches, knowledge and tools in order to control this pest efficiently. Breeding is the most sustainable approach to control broomrape in the field. A RIL population derived from a cross between HA89 and LR1, an inbred line bred from an interspecific cross with Helianthus debilis had been previously characterized for resistance to O. cumana race E, but no data is available for new races. The aim of this study was to characterize the HA89xLR1 RIL population for resistance to race F and to identify QTLs associated with this resistance. The population was phenotyped by counting the number of healthy broomrape tubercles and the rate of tubercle necrosis on young sunflower plants raised in a growth chamber with four biological replications. Differences in l resistance were observed among the RIL population, with some resistant genotypes and some highly susceptible genotypes. The polymorphism of 111 SNP markers previously mapped on a consensus genetic map was used for the QTL detection. Four QTLs were detected on four linkage groups (LG01, LG07, LG15 and LG17), with two QTLs controlling the number of tubercles per plant and two others controlling necrosis. This study suggests that the resistance to O. cumana race F is controlled by several QTLs affecting differently the number of tubercle and the induction of tubercle necrosis.This research was supported by the French Association for the Promotion of Oilseed Crops Breeding (PROMOSOL).N

Inheritance of coffee bean sucrose content in the interspecific cross Coffea pseudozanguebariae X Coffea liberica 'dewevrei'

International audienc