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RESEARCH PRODUCT

The black box of genotype/phenotype variability and its effects on plant fitness

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To answer the question of anticipating weed outbreaks, researchers use (or should use) population growth rate (Lambda) to model demographic evolution. Growth rate is depending of the most frequent genotypes in the population. Not all the plants are equivalent: besides genetics, environmental variables increase the phenotype diversity. To what extent the phenotype shapes the relative fitness of different genotypes? Fitness is the plant contribution to the next generation; it is most often evaluated through progeny size. However, in many studies, this is done regardless of the seed origin and whether the progeny would germinate or not under appropriate conditions and timing to grow as adult plants on further years. In order to estimate how phenotypes interact with genotypes and how fitness is expressed, an experiment was set up with the autogamous Setaria viridis. Physiological difference, date of emergence and plant density were chosen to shape phenotypes. A genotype suffering photosynthesis deficiency was compared to another genotype, thus anticipating different fitness according to previous studies. Seeds were multiplied on year n, planted in between maize rows and selected for simultaneous emergence with maize or ten days later on year n+1. Planting design was either isolated plant, mixed genotype pair, or mixed pair plus ten additional plants of one or the other genotype in the same patch. There was seven replicates each treatment combination. Superficial cultivation was carried out after harvest and the field was kept without crop the next years. Date and amount of emerged seedlings, each genotype being identified by collar colour, were recorded the following years n+2 and n+3. Effects of date and planting design variations on progeny sizes and emergence timing of the two genotypes are discussed. This experiment offers the opportunity for reframing the study of fitness.