Path Coefficient Analysis of Bread Wheat as Affected by Planting Dates

Abstract

A field trial was conducted in the field of Crop Science Dept., Coll. of Agric. Univ. of Baghdad during 1997-1998 and 1998-1999 winter seasons, to study the effect of sowing dates on yield and yield components of eight bread wheat cultivars. A split plot arrangement in randomized complete block design with three replicates was used. Planting dates (Oct. 25th , Nov. 19th and Dec. 14th) were assigned in the main plots, where as eight bread wheat cultivars were assigned in the sub-plots. Data collected on grains yield, tillers number/m2, ear length, number of grains / spike, 1000-grain weight and harvest index. Phenotypic correlation coefficient among grain yield and all other characters were determined, path coefficient analysis carried out to partition the phenotypic correlation coefficient to the direct and indirect effects to each planting date and season. The path coefficient analysis showed that number of tillers/m2 had the highest positive direct effect on grains yield (7.69) followed by ear length (3.92) at the second planting date (Nov. 19th). Number of spikes/m2 gave highest positive direct effect (3.18) followed by 1000 – grain weight (1.5) and ear length on grains yield (1.4) at the first planting date (Oct. 25th) where as harvest index had the highest positive direct effect on grain yield (1.91) at the third planting date (Dec. 14th). The sum of direct and indirect effect on grain yield was from ears number/m2, harvest index, ear length and tillers number/m2 at the Oct. 25th, and from harvest index, number of grains/spike, ear length and number of tillers/m2 at the Nov. 19th, and from harvest index, tillers number/m2 and number of spikes/m2 at the Dec. 14th at first season. It was concluded that the direct and indirect effects of each character on yield depends on planting date and season, depending on number of tillers/m2, number of spikes/ m2 and harvest index could be used as selection index to improve grains yield in bread wheat by selection in next generations at irrigated central of Iraq.