Exploration of late blight quantitative resistance in potato diversity: QTL meta-analysis including the novel resistance sources Solanum sparsiplum and Solanum spegazzinii

International audienc

Development of a Potato Cultivar (Solanum tuberosum L.) Core Collection, a Valuable Tool to Prospect Genetic Variation for Novel Traits

International audienceThis study presents the development of a core collection capturing the genetic diversity of a collection of 350 tetraploid cultivated potato varieties (Solanum tuberosum L.). The core collection was established by using simple sequence repeats (SSR) data and the M strategy, which aims at maximizing the allelic diversity. A 48-core collection was defined which captured 99.5% of the SSR alleles used to establish it, and 96.9% of the SSR alleles which belonged to an independent set of markers. The defined core collection was further validated by analysing 35 agro-morphological traits. The class coverage value and the estimates of the Shannon-Weaver diversity index indicated a good representation of the phenotypic diversity in the core collection. Furthermore, the core set included accessions having the most desirable status for several agronomic traits. A linkage disequilibrium (LD) analysis, using data obtained with the SolCAP SNP array on the defined core collection, was performed. The population structure analysis showed that the core collection did not present a clear genetic structure. The linkage disequilibrium analysis carried out between markers located on the same pseudomolecule within 10,000 bp concluded that 41.3% of these pairs of SNP markers have a significant LD. We conclude that this core collection, representative of the genetic diversity of cultivated potato varieties, is a relevant tool for a first screening for genetic variation regarding novel traits of interest

Resistance to late blight and soft rot in six potato progenies and glycoalkaloïd contents in the tubers

International audienc

Selection of nematodes by resistant plants has implications for local adaptation and cross-virulence

International audienceThe variability of resistance durability in different potato genotypes harbouring the same resistance QTL but differing by their genetic background was explored. The indirect consequences of the resistance adaptation in terms of local (i.e. genotype-specific) adaptation and cross-virulence was also investigated. Following the virulence of the potato cyst nematode Globodera pallida in a long-term experimental evolution protocol, the results showed that nematode populations were able to adapt to the resistance of four potato genotypes carrying the QTL GpaV from Solanum vernei, and that the plant genetic background has an impact upon the durability of resistance. The pattern of local adaptation observed here indicates that divergent selection has occurred during the experimental evolution performed from the same initial nematode population, and revealed a trade-off between the adaptation to a resistant potato genotype and the adaptation to another resistant genotype differing in its genetic background. In terms of cross-virulence between potato genotypes derived from different resistance sources (S. sparsipilum and S. spegazzinii), this study shows that the adaptation to resistance QTL GpaVvrn does not necessarily allow the adaptation to collinear GpaV loci. The results presented here could be useful for predicting evolution of nematode populations in natural agro-ecosystems and identifying durable strategies for resistance deployment

Genetics and phenotypic characterisation of the hypersensitive resistance of Solanum sparsipilum to Meloidogyne incognita

International audienceThe hypersensitive resistance of the genotype '385.484.13' of Solanum sparsipilum to Meloidogyne incognita, one of the southern root-knot nematodes and their Mi virulent populations was analysed. Genetic control of the hypersensitive reaction was assessed based on segregation of the necrotic reaction in infected roots of diploid F1 plants obtained from the cross of the genotype '385.484.13' with the dihaploid susceptible potato genotype 'Keltia H12'. Two distinct tests showed a distorted segregation compared to the hypothetical ratio expected for a monogenic control. We hypothesised that the resistance is based on one dominant gene designated Mh and linked to the self incompatibility locus-S. Hypersensitive plants prevented juveniles from feeding, developing and reproducing. Ninety percent of invading juveniles remained undeveloped 6 weeks after inoculation. Almost all the adults were males and only very rarely were females observed. Inhibition of the development of juveniles into females showed a bimodal distribution of the genotypes: hypersensitive ones allowed almost no development of females whilst all the juveniles became females in nonhypersensitive plants. That result supports the hypothesis of a monogenic control of the resistance. The resistance was broken when plants were grown at 30 degrees C. The histology of the hypersensitive reaction was very similar to that of the Mi gene of tomato and of some Me genes of pepper. Necrotic cells were localised not only around the head of the juveniles but also surrounding their bodies. In addition, healthy cells adjacent to necrotised ones underwent divisions parallel to the juveniles. Intercellular spaces between these cells and necrotised ones enlarged markedly, which is consistent with a process leading to isolation of the necrotic area from healthy tissu

Durabilité et stratégie de sélection pour la résistance aux nématodes à kyste chez la pomme de terre

National audienc

Efficacité, durabilité, productivité : la recherche du compromis - Cas du couple pomme de terre-nématode à kyste Globodera pallida

National audienceResistant varieties represent a cost effective and environmentally friendly means to control many pests. They are therefore used extensively as a crop protection strategy. Developing such resistant varieties to control potato cyst nematode Globodera pallida is of paramount interest, especially because of its quarantine status and the obligate management of infested fields. A good resistant variety is the result of the best trade-off between efficiency (against the widest range of the nematode populations), durability (as the variety must provide an efficient protection during repetitive cropping periods) and yield performance (in particular in the presence of nematodes). Presently, only one G. pallida resistant variety, Îledher, is registered in France. Its resistance comes from the related wild species Solanum vernei and the evaluation of its durability under laboratory conditions showed that only five nematode generations were sufficient to select virulent individuals. Our main goals are thus to identify among different related wild species of Solanum (Solanum vernei, S. sparsipilum and S. spegazzinii), new genotypes that can be used as resistant parents for future varieties that will present the best trade-off between efficiency, durabilty and agronomical characteristics and also be able to control the virulentpopulations selected on the variety Îledher, if ever they appeared in the fields.L'utilisation de variétés résistantes constitue un idéal à atteindre en termes d'agriculture durable, en particulier vis-à-vis de Globodera pallida. Ce nématode, strictement inféodé aux solanacées et plus particulièrement à la pomme de terre, provoque des dégâts tant qualitatifs que quantitatifs. Outre son importance économique, G. pallida fait l'objet d'une lutte obligatoire en Europe et dans le monde de par son statut de ravageur de quarantaine. La mise au point de variétés résistantes passe par la recherche du compromis idéal entre efficacité vis-à-vis d'une gamme la plus étendue de populations de G. pallida, durabilité en proposant des variétés dont les résistances ne sont pas contournées rapidement et productivité en assurant de hauts niveaux de rendement en présence du parasite. Pour le moment, une seule variété de consommation résistante à ce nématode est inscrite au catalogue français (Îledher).Cette résistance, provenant de Solanum vernei, s'avère peu durable : cinq générations permettent de sélectionner des individus virulents et d'observer un début de contournement. Nos objectifs sont donc d'identifier la ou les sources susceptibles de fournir des génotypes pouvant prendre le relais de la variété Îledher et présentant un bon compromis entre caractéristiques agronomiques, efficacité et durabilité des résistances

Quelles associations de QTL chez la pomme de terre pour une résistance efficace et durable au nématode à kyste <em>globodera pallida</em> ?

National audienceActuellement, les variétés de pomme de terre résistantes au nématode à kyste Globodera pallida inscrites au catalogue français sont peu nombreuses et proviennent toutes de l a source Solanum vernei . Il existe deux autres sources , S. sparsipilum et S. spegazzinii qui ont en commun avec S. vernei un QTL à effet fort ( GpaV ) cartographié sur le chromosome V. La source S. sparsipilum se distingue des deux autres par la présence d’un QTL à effet faible ( GpaXI spl ) qui quand, il est associé à GpaV sp l transforme la réaction de masculinisation en un blocage des larves dans les racines. Cette combinaison procure, aux clones qui la possèdent, une efficacité et une durabilité plus important e. L’INRA, en collaboration avec les sélectionneurs français, et la Coopérative de Noirmoutier a développé et testé des constructions génétiques innovantes, associant le QTL à effet faible GpaXI spl aux QTL GpaV issus des deux autres espèces. Dans la majori té des cas et quelque soient les sources de résistance, l’association du QTL GpaXI spl et du QTL GpaV conduit à un blocage précoce des nématodes. Cette association permet également de contrôler des populations virulentes au QTL GpaV vrn qu’elles soient obtenues expérimentalement ou d’origine naturelle . Ces résultats donnent des bases pour construire de nouvelles combinaisons génétiques qui permettront d’élargir le spectre d’efficacité des variétés, dans le temps et dans l’espace

Molecular marker development for introgression of nematode resistance in potato breeding programs: exploitation of [i]solanum spegazzinii[/i] resistance source

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