Effects of drought and recovery from drought stress on above ground and root growth, and water use efficiency in sugarcane (Saccharum officinarum L.)

Physiological traits associated with drought tolerance are useful as surrogate traits for drought tolerance. Information on the association of root traits and water use efficiency (WUE) and plant growth in sugarcane is rather limited. The objective of this study was to evaluate genotypic variation for root traits, WUE and growth characters of above ground parts of sugarcane. A 2 × 10 factorial experiment was set up in a randomized complete block design with two replications for three pots per experimental unit in a greenhouse during January to May 2009. Ten sugarcane cultivars were assigned as factor A and two water regimes (well-watered control and water stress at early growth stage) were assigned as factor B. Data were recorded for root length, root surface area, root volume, root dry weight and relative rate of height growth (RHG) at 10 days after dehydration (100 days after planting; DAP) and 10 days after recovery (110 DAP). Data for water use efficiency and root dry weight were recorded at 110 DAP. Stalk diameter was measured at 90 DAP, 100 DAP and 110 DAP. Drought significantly reduced stalk diameter, biomass, root length, root surface area, root volume and root dry weight, but it did not significantly affect root/shoot ratio, WUE, and RHG. Higher phenotypic variations for root traits were observed after recovery and variation of WUE and biomass were also significant. Associations of root traits with biomass and WUE were higher after recovery than before initiation of drought and at drought. The genotypes 03-4-425 and Phill6607 had higher WUE and large root systems. Root traits are useful as surrogate traits for WUE in sugarcane.