Sesame (Sesamum indicum L.) Early Root Response to Waterlogged and Water Deficit Soil Conditions

Sesame is a critical crop contributing to food security in multiple developing countries around the world. Due to the widely described drought tolerance of the crop, it is a primary choice for cultivation in arid climates. Some studies also indicate its low tolerance to hypoxic conditions when soil water content is high. However, as global precipitation patterns become more unpredictable, sesame is increasingly exposed to waterlogged conditions. Very little is known about the response of sesame root systems to extremely low or high soil water contents, but establishing this knowledge is critical for breeding efforts aimed at selecting cultivars for site-specific conditions. To address this research need, root bioassays of six sesame cultivars were conducted in a greenhouse to quantify early root development under four different soil water content conditions: 60, 80, 100 and 120% of soil water holding capacity. Digital images were collected and analyzed for total root length, number of lateral roots and root growth velocity. Preliminary results showed that the 60% moisture content lead to significantly (P<0.05) smaller roots compared to the other moisture levels across sampling dates. A trend was present and consistent across sampling dates that 80% water content led to longer roots, on average, than the other moisture levels. A significant difference (P<0.05) in cultivars was present at only one of the sampling dates, but an overall trend distinguishing cultivars was consistent across sampling dates. Further replications of this experiment will be conducted to confirm these first results. This trial will be among the firsts to document sesame rooting behavior and quantify early root architectures among a diverse set of genotypes. This will represent an important step in developing new breeding strategies accounting for root traits, in order to select for more drought and/or waterlogging tolerant sesame cultivars.