Genotypic and seasonal variation in root depth development during establishment of C4 perennial grass ecotypes

Abstract

Context Perennial forage grass species are often grown with limited water following establishment and rely on accessing water deep in the soil profile to survive. Aim This study aimed to characterise bermudagrass (Cynodon spp.) genotypes with rapid vertical root growth associated with post-establishment survival. Methods Twelve bermudagrasses representing genotypes from diverse climate zones in Australia were established in rhizotrons to analyse the stability in genotypic variation in root and shoot growth in winter and summer experiments. Genotypic rank of root length, leaf area, and root dry weight were consistent in both seasons. Key results Bermudagrass genotypes exhibited different traits correlated with root vertical growth rate and inconsistency of genotypic rank of shoot growth. During winter establishment, the rate of root depth development (RRDD) (r=−0.64) was correlated with the proportion of root length that became inactive, that was likely due to seasonal root death in winter conditions; during summer establishment, RRDD was correlated with tiller appearance rate (r=0.45) and root distribution to 10cm depth (r=−0.62). Shoot dry weight was correlated with photosynthesis (r=0.85) and transpiration (r=0.79) in summer, but not in winter. RRDD (r=0.75, winter and r=0.77, summer) was correlated with drought resistance index, previously analysed under field conditions. Conclusions and implications Genotypes from the Mediterranean climates in Australia showed rapid growth of roots and shoots in both seasons and have the greatest potential for broader application for forage production in variable environments.