Grain yield improvement in bread wheat (triticum aestivum l.)by single plant selection from different segregating populations

The breeder must choose an effective selection method that would facilitate the simultaneous improvement of yield and yield components. The main aim of this study was to measure the effectiveness of single plant selection method (SPS) in predicting the potential of different crosses in respect of yield improvement of bread wheat (Triticum aestivum L.). Forty-eight lines of wheat were selected visually from F 2 and F 3 generations of twelve crosses, both populations were advanced to the F 4 and F 5 generations and evaluated during two cropping seasons 2005/06 and 2006/07, at the Gezira Research Station Farm (latitude 14 deg C 24 N, longitude 33 deg C 31 E, altitude 411m), Wad Medani, Sudan. The two evaluation experiments (2005/06 and 2006/07) consisted of the lines and their respective two parents in addition to the bulk populations from which they were originated and four local varieties: Elnelain, Debeira, Imam and Condor. The tested material was arranged in an augmented design with six blocks. In both seasons, there were differences between the lines and the checks and among the lines themselves, differences were attributed to selection methods, and to methods vs. the tested lines and for all yield traits studied. The seasonal variations resulted in clear differences in yield and yield components of the checks and the parental lines. Results revealed that the unselected bulk populations were effective in the early generations (F3 and F4), whereas, the single plant selection method was more effective for improvement of yield and yield components during the late generations (F4 and F5). On the basis of grain yield in both seasons, the results demonstrated that most of the top ranked new lines were Elnelain derivatives. The parental line Group No.16 was the highest yielder for the two seasons. It was found that, one and four lines significantly out yielded the highest yielder check in the first and the second seasons, respectively. Correlation analyses in the first season indicated that grain yield was significantly and positively correlated with number of tillers per square m and yield per single plant. Positive and non significant associations were detected between number of grains per spike and 1000 grain weight. But there was non significant and negative correlation between grain yield and plant height. Path coefficient analyses depicted that tillers square m and yield per single plant had positive direct effect on grain yield. With the regard to the second season, correlation analysis indicated that grain yield was significantly (P0.05) and positively correlated with number of tillers per square m, yield per single plant, grains per spike and 1000 grain weight. Positive and non significant associations were detected between plant height and grain yield. Moreover, Path coefficient analyses depicted that number of tillers per square m, yield per single plant, grains per spike and 1000 grain weight had positive direct effect on grain yield