Influence of fungal genotypes and fungal and plant phenotypes in the arbuscular mycorrhizal symbiosis
Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of plant roots. They obtain and then exchange important plant nutrients as phosphate and nitrate for plant carbohydrates. Indeed, it has been shown that the mycorrhizal fungus Rhizophagus irregularis enhance growth of crops like rice (Colard et al., 2011) and Cassava (Ceballos et al., 2013). Thereby, using AMF as a tool for plant growth enhancement, these fungi could be a natural alternative helping to reduce the need for chemical fertilizers.
3D- reconstruction of the fungus Rizophagus irregularis with its host (Made with ImageJ)
However, little is known about the molecular basis for how variation in the fungal genotype influences plant growth. Doing traditional QTL analysis is not possible with R. irregularis, because this fungus is haploid and does not appear to follow a normal pattern of mendelian inheritance. However, an association mapping approach between phenotypes and genotypes could help to detect quantitative trait loci (QTL) (Hambling et al., 2011). This would be a prerequisite for developing a fungal breeding project that will focus on enhancing crop growth.
So, understanding the relationship between the fungal genotype and phenotype, and the association between the fungal genotype and the plant phenotype is the main aim of my PhD.
Consequently, the questions that i am testing for my PhD are:
1) Is there a correlation between the fungal genotype and its phenotype?
2) Which traits of the fungal partner influence plant growth?
3) What sets of markers in the fungal genome are associated with plant growth?
4) What is the evolutionary unit of R. irregularis?
Relevant references
Ceballos, I., Ruiz, M., Fernández, C., Peña, R., Rodríguez, A., & Sanders, I. R. (2013). The In Vitro Mass-Produced Model Mycorrhizal Fungus, Rhizophagus irregularis, Significantly Increases Yields of the Globally Important Food Security Crop Cassava. (M. Rillig, Ed.)PLoS ONE, 8(8)
Chagnon, P.-L., Bradley, R. L., Maherali, H., & Klironomos, J. N. (2013). A trait-based framework to understand life history of mycorrhizal fungi. Trends in plant science, 1–8
Croll, D., Wille, L., Gamper, H. a, Mathimaran, N., Lammers, P. J., Corradi, N., & Sanders, I. R. (2008). Genetic diversity and host plant preferences revealed by simple sequence repeat and mitochondrial markers in a population of the arbuscular mycorrhizal fungus Glomus intraradices. The New phytologist, 178(3), 672–87. doi:10.1111/j.1469-8137.2008.02381.x
Denison, R. F., & Kiers, E. T. (2011). Life histories of symbiotic rhizobia and mycorrhizal fungi. Current biology : CB, 21(18), R775–85
Ehinger, M. O., Croll, D., Koch, A. M., & Sanders, I. R. (2012). Significant genetic and phenotypic changes arising from clonal growth of a single spore of an arbuscular mycorrhizal fungus over multiple generations. The New phytologist, 853–861. doi:10.1111/j.1469-8137.2012.04278.x
Filiault, D. L., & Maloof, J. N. (2012). A Genome-Wide Association Study Identifies Variants Underlying the Arabidopsis thaliana Shade Avoidance Response, 8(3). doi:10.1371/journal.pgen.1002589
Hamblin, M. T., Buckler, E. S., & Jannink, J.-L. (2011). Population genetics of genomics-based crop improvement methods. Trends in genetics : TIG, 27(3), 98–106. doi:10.1016/j.tig.2010.12.003
Sanders, I. R., & Croll, D. (2010). Arbuscular mycorrhiza: the challenge to understand the genetics of the fungal partner. Annual review of genetics, 44, 271–92. doi:10.1146/annurev-genet-102108-134239
