Characterization of Drought Tolerance Traits in Corn and Sorghum: A Phenotypical Approach.

Soil-water availability is a major factor determining growth, development and yield of corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench). Limited soil-water availability during reproductive phase may lead to defoliation, decrease in staygreen period, reduction in biomass and grain yield, etc. These problems raise the importance of crops that can withstand limited soil-water availability and produce good yield. Drought tolerant genotypes that can grow and yield well in a particular soil are needed. To identify such genotypes of corn and sorghum, these crops were grown in two different irrigation regimes (full irrigation and deficit irrigation) in Uvalde during summer 2016. Soil-water availability was measured by neutron probe. The 15 genotypes of corn that were sown consisted of one tropical derived, one mostly temperate derived, and ten tropical-temperate derived experimental hybrids and three commercial checks. The sorghum genotypes consisted of seven inbred lines and eight hybrids. These genotypes were compared based on different physiological characteristics such as biomass, harvest index, leaf area index, chlorophyll content, sap flow, yield/area etc. The field plots received 10.95 inches of precipitation from planting to harvesting period in year 2016. Statistical analysis (based on 95% confidence) showed no significant interaction between genotype and irrigation regime. Effect of irrigation regime was also found to be non-significant in both corn and sorghum. Significant differences were observed among genotypes as a result of their genetic characteristics. Corn experimental hybrids GP7169GT/Tx777, NP2643GT/Tx777, and Tx781/Tx777 performed better for most of the parameters measured such as plant height, yield/m², harvest index, total plant weight, water use efficiency, etc. Commercial genotypes produced better grain yield than experimental hybrids. Better performance was observed in hybrid sorghum genotypes ATx645/RTx437 and ATx623/RTx430 and inbred sorghum genotypes B.Tx623 and B.Tx645 for several physiological traits. The experiment is being replicated in 2017 with additional measurements of leaf osmotic potential and canopy NDVI.