Title : Estimation of genetic parameters of a Miscanthus sinensis population: A staggered-start design highlights a greater effect for climate than age
Bioeconomy, sustained by agriculture and breeding, belongs to innovative solutions to address current challenging environmental issues. Miscanthus, a dedicated perennial crop, is known to display interesting traits to produce renewable resources (Clifton-Brown_et_al._2001._Agronomy_Journal): a high biomass production and quality, coupled with low inputs needs. However, the improvement of these traits requires to assess their heritabilities. Due to the perennial feature of the crop, the year effect confounds the age and climate effects, which hampers the assessment of the corresponding variances and heritabilities. In the framework of the BFF1 project, we evaluated a Miscanthus sinensis population focusing on two main questions. What are the plant age and climate effects on the expression of miscanthus genetic diversity? Are they different for each trait and what are the lessons for miscanthus breeding? A Miscanthus sinensis mapping population of 159 genotypes was established with its two parents in France in two contrasted sites. On each site, the establishment was staggered over two years: a first group of genotypes was established in 2014 and its establishment was repeated in 2015. Such a design, called “staggered-start design” (Loughin_2006._Crop_Science) is relevant to evaluate perennial crops: it indeed allows decomposing the year effect in two components, the age effect and the climate effect. Due to plant losses and in vitro propagation recalcitrance for some genotypes, the design was unbalanced as all individuals were not established twice. For each establishment, year and location, phenotyping data consisted in biomass production and quality related traits. Corresponding genetic parameters were computed through Linear Mixed Models using breedR software (Muñoz and Sanchez. 2019). Regarding canopy height and plant maximum height, the mean “genotype x climate” interaction variance estimates across ages were up to 1.5 times higher than the mean “genotype x age” interaction variance estimates across years, for both locations. Concerning hemicellulose (%DM) and cell-wall content, the mean “genotype x climate” interaction variance estimates across ages were respectively up to 2.5 and 6 times higher than the mean “genotype x age” interaction variance estimates across years, in Orléans. These results displayed here show substantial effects of plant age, climate and location on the expression of miscanthus genetic diversity, through all biomass production and quality traits studied. This generated variations in heritability estimates and this could imply to detect distinct QTL and to discuss the implications in breeding.