Evaluation of drought tolerance of winter bread wheat genotypes under drip irrigation and rain-fed conditions

To evaluate the genetic diversity in 48 winter bread wheat genotypes originating from different countries, an experiment basedon randomized complete block design with 4 replications was carried out in drip irrigation and rain-fed conditions at the field stationof the Transitional Zone Agricultural Research Institute, Eskiºehir, Turkey in 2011 and 2012. Based on grain yield under rain-fed andirrigated conditions, drought tolerance indices, i.e. stress susceptibility index (SSI), stress tolerance index (STI), tolerance index (TOL),mean productivity (MP), and geometric mean productivity (GMP), were calculated to identify genotypes with better yield and droughttolerance. Analysis of variance indicated that there were highly significant differences among the genotypes with regard to all the traitsunder the two experimental conditions. The correlation coefficients showed that STI, MP, and GMP were the most desirable selectioncriteria for high yielding and drought tolerant genotypes. Based on principle component analysis and biplot, genotypes numbered as6, 11, 26, 41, 45, and 47 were susceptible genotypes. The genotypes numbered as 4, 12, 17, 24, 27, 28, 34, 35, 36, 38, and 42 were morestable under rain-fed conditions, while genotypes numbered as 9, 29, 31, and 44 were highly adapted to the irrigated conditions. Clusteranalysis classified the genotypes into 3 groups: resistant, susceptible, and tolerant to drought conditions. In conclusion, this studyshowed that drought stress reduced the yield of some genotypes, while others were tolerant to drought, suggesting genetic variabilityof drought tolerance in this material. Therefore, breeders can select stress-resistant wheat genotypes based on the MP, GMP, and STIindices.