Plant performance: a physiological and genetic analysis using Arabidopsis thaliana natural variation

Plant performance implies complex traits, controlled by a large set of genes and affected by the environment. In this thesis we have tried to take the first steps in unravelling the genes controlling plant performance using naturally occurring accessions (ecotypes) of the model plant Arabidopsis thaliana and QTL (quantitative trait locus) analysis.Traits associated with plant performance (mainly the gain, the allocation, and the storage of carbon) have been studied to investigate if there is a relationship between various growth parameters, and between growth and flowering-related traits. We found limited variation for photosynthetic performance (measured as chlorophyll fluorescence) with the exception of the Ely accession. The difference in the growth parameters and the photosynthetic traits observed between Ely and the standard accession Landsberg erecta was probably due to the fact that the D1 protein of Ely encoded by the psbA gene, was mutated, leading to atrazine-resistance.Based on the natural variation that we found within Arabidopsis accessions for different traits that relate to plant growth, carbohydrate content and flowering time,four new recombinant inbred line (RIL) populations(L er x An-1, L er x Kas-2, L er x Kond and L er x Sha)of Arabidopsiswere developed and genotyped.QTL analysis for flowering time revealed12 to 16 different QTLs segregating for flowering time in these four populations.QTL analysis, using the RILs derived from the cross between L er and Sha, revealedfive genomic regionswhere QTLs for growth traits (plant areas, dry weight and RGR) are located.QTL analysis, using the RILs derived from the cross between L er and Kond that were grown on hydroponics, also revealed QTLs for the different aspects of plant growth-related traits, sugars and starch contents and flowering-related traits. From the significant correlations and the co-locations of the QTLs for these aspects, we conclude that there is a complex relationship between plant growth-related traits, carbohydrate content and flowering-related traits.This study shows that Arabidopsis natural variation can successfully be used to study the genetic basis of these complex traits.