Genotypic variation in root distribution changes and physiological responses of sugarcane induced by drought stress

Drought is an important factor reducing yield and quality of sugarcane. Root growth and physiological traits are important for maximizing water uptake to improve drought resistance. This study compared the root, shoot and physiological traits under drought stress (DS) and well-watered (WW) conditions of various sugarcane varieties grown in rhizoboxes in a greenhouse at the Field Crops Research Station of Khon Kaen University, Khon Kaen, Thailand. Data were recorded for the root, shoot and physiological traits (relative water content, stomatal conductance, SPAD chlorophyll meter reading and chlorophyll fluorescence) at 90 days after transplanting. Root samples were recovered from 11 soil layers at 10 cm intervals from the top to the bottom of the rhizobox, for root length and root dry weight measurements. Drought was imposed on sugarcane at early growth stages altered the root distribution patterns, and differences were evident among the sugarcane genotypes. The sugarcane genotypes adapted to water stress by increasing root length into deeper soil layers. Drought led to increased total root length in KK3, MPT06-166, K88-92, CP38-22, Kps01-12 and KPK98-40. Root lengths and stomatal conductance were positively correlated under WW and DS conditions. Root distribution in the lower soil layers and the percentage of root distribution were higher than those under well-watered conditions. The knowledge gained from this study will aid parental selection in sugarcane breeding programs for drought resistance as the findings strongly suggest that the physiological modification in the root system is a useful drought-resistant mechanism.