Description succincte
(Anglais)
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The inherent genetic diversity of maize provides a powerful material for allele mining associated with traits of interest (Buckler et al., 2006). An association population of a total of 302 maize lines has been generated that represent the genetic diversity in lines from public-sector maize breeding programs worldwide and include current breeding lines as well as historically relevant lines from temperate and tropical programs (Flint-Garcia et al., 2005). This population captures most alleles of cultivated and provides a powerful tool for high resolution association mapping allowing to zoom in at individual genes or nucleotides. It is well known that plants vary in their responsiveness to AM colonization (Johnson et al., 1997). In a novel genetic screen we intend to address traits related to functionality of the symbiosis by examining a collection of genetically diverse maize lines for their responsiveness to mycorrhizal colonization. Dry weight (dw) will be measured and total phosphorus content will be compared from tissue of mycorrhizal and non-mycorrhizal control plants as an expression of responsiveness to AM colonization. We will concentrate on genotypes displaying high responsiveness to the AM symbiosis in the absence of dependence (Janos, 2007). To unravel the molecular mechanisms determining mycorrhizal responsiveness is aim of the projected work. Classical QTL mapping on available and self-generated populations will be combined with novel association mapping. Allele diversity will be determined for the key phosphate (Pi) uptake protein ZmPHT1;6 using the association mapping population in order to identify the biologically relevant polymorphisms.
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Partenaires et organisations internationales
(Anglais)
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AT, BE, CH, CZ, DE, DK, ES, FI, FR, GR, HU, IE, IL, IT, NL, NO, PL, PT, RO, SI, SK, TR, UK
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Résumé des résultats (Abstract)
(Anglais)
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Maize is economically one of the most important crops. The inherent genetic variation of maize provides an ideal tool for allele mining associated with the trait of interest for improving germplasm via molecular breeding. In a novel genetic screen we addressed traits related to functionality of the arbuscular mycorrhizal (AM) symbiosis by examining a collection of 30 genetically diverse maize lines for their responsiveness to mycorrhizal colonization. Our trait of interest therefore refers to nutrient use efficiency focusing in particular on phosphate (Pi). We analyzed variation in mycorrhiza effect on the basis of overall shoot biomass production using a linear model developed in my laboratory during previous years of the COST funding. Favorite lines were identified that displayed contrasting phenotypes, i.e. low and high responsiveness to AM colonization. We aim at the identification of superior alleles underlying enhanced mycorrhizal responsiveness. Complementary approaches rely on co-localizing QTL confidence intervals and polymorphism in candidate genes that contribute to phenotype variation. Our candidate genes of choice are mycorrhiza-induced phosphate transporters of maize. We computationally retrieved the sequences corresponding to the complement for the maize PHT class of transporters and determined their expression pattern in the sequenced genotype B73 in the presence and the absence of mycorrhizal colonization. Surprisingly, the profile of AM-regulated Pi-transporter proteins of maize diverges from rice and dicotyledonous hosts of AM fungi, thus indicating that symbiotic Pi acquisition in maize is more complex than in other hosts of AM fungi described so far.
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