Assessing Tetraploid Bahiagrass Productivity From Root Screenings.

Bahiagrass, Paspalum notatum Flüggé, is a perennial C₄ species extensively cultivated as forage and turf in southeastern USA. The identification of ecological factors affecting biomass yield will enhance the genetic improvement of this species. Several root characteristics are suspected to play a major role on crop production. The objective was to evaluate the relevance of the rate of root depth development (RRDD), root length density (RLD) and root mass on bahiagrass biomass production. Thirteen apomictic tetraploid clones, including cultivars and novel hybrids (potential new cultivars), were used. The RRDD was evaluated by measuring root depth over time when clones were grown in clear acrylic columns. Greater RRDD was observed for one novel hybrid (FL-122). Greater root and shoot mass was also observed for this hybrid at the end of the experiment, indicating that RRDD was associated with early vigor. Root mass and RLD were analyzed at different soil depths when clones were grown in field plots. Genetic variability for RLD was observed only during the second year. When 360 kg N ha^-1 year^-1 was applied, genotypic differences for RLD were observed at the 0- to 40-cm and 40- to 80-cm soil depths. In contrast, genotypic variability for RLD was only observed at the 80- to 120-cm depth when 120 kg N ha^-1 year^-1 was applied. Although the rate of fertilization had a marked effect on forage yields, it did not affect root mass. No significant correlations were found between RLD or root mass and forage yields. The results indicate that breeding for a deeper but less massive root system in the top soil might result in cultivars better adapted to semi-intensive production systems.