An Index of Competition Reduces Statistical Variability and Improves Comparisons between Genotypes of Miscanthus

Abstract

It is important for breeders and producers to be aware of competition effects for variety trials. We aimed at developing an index of competition to reduce statistical variability in field trials and improve comparisons between genotypes of Miscanthus. Twenty-one clones belonging to four species of Miscanthus (M. x giganteus, M. floridulus, M. sinensis, and M. sacchariflorus) planted at the same density were compared at two harvest dates during the second and third crop years. Aboveground volume was shown to be a good predictor of the aboveground biomass of the clones, and was analysed for the competition effect. The best competition index was the ground area occupied by the eight neighbour plants, among the four indices defined as covariates in the statistical models. It reduced the root mean square error of the aboveground volume by as much as 17 %, explaining up to 36 % of the residual error of the model. Our results then concerned the contribution of intragenotypic competition of Miscanthus to the variability between plants of a same clone during field trials, the relationship between competition ability and plant traits, and the comparison of genotypes regarding this competition. All clones showed negative competition sensitivities depending on harvest date, crop year, and clone. The competition effects lead to reduction in mean aboveground volume by up to 17 %. Competition sensitivities were strongly correlated with aboveground development (height and yield) in both crop years, whatever the harvest dates. In Miscanthus field trials, using a competition index may help to reduce statistical variability and improve comparisons between genotypes.

Early Prediction of Miscanthus Biomass Production and Composition Based on the First Six Years of Cultivation

“…The aboveground plant volume index (expressed in cm 3 ) was calculated as a function of the canopy height, stem number per plant, and stem diameter according to Zub et al (2012a):…”

“…In addition, Zub et al (2012a) reported that the aboveground plant volume index of Miscanthus was a reliable predictor of the biomass produced in the second and third years. Our results confirmed these findings over a longer time period (from the second to the sixth year).…”

“…Furthermore, biomass production is highly and positively correlated with the flowering date, canopy height, and stem diameter (Zub et al, 2011). In addition, the aboveground volume of the plant has been identified as a reliable predictor of biomass production for the second and the third years of cultivation (Zub et al, 2012a).…”

Miscanthus Genetics and Agronomy for Bioenergy Feedstock

“…In addition, Zub et al [150] found that the aboveground volume including the stem number, the stem diameter and the plant height was a good predictor of plant biomass yield. Within genotypes, strong positive relationships were observed between biomass yield and the aboveground volume regardless of crop year (equal to 0.70 and 0.82 for autumn and winter harvests during the second year, respectively).…”

“…In Miscanthus, the residual term was high during the second and third years of the crop (Zub et al [150]) and could hamper inter-genotypic comparisons for traits such as aboveground biomass yield or related traits. Without more plots or samples (it is indeed important for the breeder and the producer to save place and cost), one way for reducing the residual term is to take into account intra-genotypic competition effect in the statistical model [150]. As it implies observations at the plant level, intragenotypic effect assessment requires easyto-measure variables, such as the stand volume as a predictor of the aboveground biomass [150,151].…”