Estimating the Genetic Parameters of Flowering-Time Related traits in a Miscanthus Sinensis population tested with a staggered-start design

Abstract There is a growing interest in the cultivation of miscanthus on marginal land, but biomass yields are much lower there than on good farming land. Therefore, understanding what causes such instability is of primary interest for breeding later-flowering but stable miscanthus genotypes. Our objectives were to estimate the genetic parameters -genetic variance and genetic heritability- and genetic correlations for flowering-time-related traits in a biparental Miscanthus sinensis diploid population, and to divide the year effect into both age and climate effects using a staggered-start design. The population was established with single plants organized in a staggered-start design and consisted of two genotype groups established twice, in 2014 and 2015, with a total of 159 genotypes and 82 common genotypes between the two groups. All plants were extensively phenotyped for different panicle and anther emergence traits in 2018 and 2019. All traits were delayed by about 20 days in 2019 compared to 2018, which was explained by climatic conditions that occurred before the floral transition, mainly by a 3°C decrease in maximal and minimal temperatures. When dividing the year interaction effect, the genotype × climate interaction was much higher than the genotype × age interaction. The climate effect not only caused a delay in the flowering time but also involved differential genotype behavior through climate × genotype interactions, which increased the corresponding genotype × climate interaction variance compared to the genotype × age interaction variance: the climate effect decreased the genetic parameters for all flowering-time related traits, up to 20 % for broad-sense heritability. Interestingly, all traits responded similarly to the climate effect, excepting the interval between the start of panicle emergence and that of anther appearance, for which the correlation coefficients were lower due to significant climate interactions, compared to genotype × age interactions. Therefore, M. sinensis breeding for flowering-time related traits must be conducted under contrasted climates in order to select more stable genotypes.