Evaluation for grain yield in regional preliminary yield trials and selection in segregating generations in bread wheat genotypes under limited water conditions in cold regions Evaluation of bread wheat genotypes in advanced yield trials in cold regions under limited water conditions

Terminal drought stress is one of the limiting factors of wheat production in cold regions of Iran. Selection and introduction of terminal drought tolerant cultivars is one of the major goals of wheat breeding program for cold dry areas of Iran. Considering the importance of terminal drought stress and shortage of water at terminal growth stage of wheat cultivars, different types of yield trails are conducted under optimum and limited water conditions to identify and introduce cultivars which have the ability to produce expected high grain yield under limited water conditions. The objective of this study was to select terminal drought tolerant wheat lines with high grain yield and good adaptability in Advanced Regional Wheat Yield Trial (ARWYT) under limited water conditions in cold regions. This study was conducted in two series of experiments as follows: 1-Uniform Regional Wheat Yield Trial (URWYT) were conducted with 35 wheat lines including three checks (Toos, Cross Shahi and Toos) in two separate experiments (ARWYT-D1 and ARWYT-D2) using randomized complete block design (RCBD) with 3 replicates under late season limited water conditions in 6 experimental stations (Karaj, Ardabil, Hamedan, Miandoab, Tabriz and Mashad) in 2004-2005 cropping seasons. Trials were irrigated by just the heading stage. 2-High Yielding and Advanced lines Trials of IRAN/ICARDA project: Both Advanced lines Trial and High Yielding Trial were conducted with 110 wheat lines including checks using alpha lattice design with 2 replicates in two separate experiments under late season limited water conditions at Karaj station. During cropping seasons, morpho-physiological and agronomical characters associated with drought tolerance such as plant height, growth habit, no of kernels/spike, 1000 kernel weight, no of days to heading and maturity, and grain yield were recorded. Comparisons of grain yield of new lines in UARWYT trials in each station and determination of their yield stability was carried out using non-parametric ranking statistic method (rank method). Based on results, most new lines were superior to the check cultivars in both of the two series of the experiments. However, considering both the recorded data, and the grain yield of wheat lines under limited water conditions, 8 superior lines were selected from URWYT. These selected lines will be assessed for their adaptability and yield stability under terminal drought stress conditions in next year’s cropping season. From High Yielding and Advanced lines Trials, 140 new lines were selected for Regional Yield Trials in the next year’s cropping season.