The study of agronomic characters relationships withGMP index of rapeseed (Brassica napus L.) yield by Sequential Path Analysis

In order to study of cause and effect relationships of agronomic characters in water stress and water non-stress conditions with Geometric Mean Productivity index (GMP), a research was conducted in experimental field of agriculture faculty of zanjan university in the year 00. In use experimental design was split block design based RCBD with three replications that irrigation with two levels (water non - stress and water stress) and rapeseed variety in sixteen levels were experimental factors. The results of sequential path analysis indicated that for selecting under water non-stress conditions in order to breeding for grain yield GMP, increase of number of branches and siliqua per plant and decrease of 000-grain weight was necessary. Due to relationship of these three characters, it is necessary to put them in equilibrium together. Also for selecting under water stress conditions, increase of seeds per siliqua and siliqua per plant and decrease of days to flowering. was necessary. Indirect breeding for oil yield GMP in water non-stress conditions was possible by breeding to increase branches number and siliqua per plant and to decrease of 000-grain weight and, in under water stress conditions by breeding to increase of seeds per siliqua, siliqua per plant and oil content.