Response of Performance and Combining Ability of Wheat Parents and Their F2 Progenies for N Efficiency Traits to Reducing N-Fertilizer Level
Abstract
Because of high production cost of nitrogen (N) fertilizer and prevention of environmental pollution, it is
important to improve N use efficiency (NUE) of wheat (Triticum aestivum L.). The objective of this study was to
evaluate NUE traits of 6 x 6 diallel wheat F2 progenies and parents at low (LN, no N fertilizer) and high (HN,75 kg
N/fed) N levels. Two experiments were conducted during two seasons, the 1st under HN and the 2nd under LN using
RCBD in three replications. Data analyzed across seasons indicated that L25, L26 and L27 showed high values of
nitrogen use (NUE) and uptake (NUPE) efficiency and the best general combining ability (GCA) effects for these
traits. The best F2 crosses in per se performance and specific combining ability (SCA) effects were L26 x Gz168,
L27 x Gem7, L26 x L27 and L25 x Gz168). Mean squares due to both GCA and SCA were significant under both
low-N and high-N for all NUE components, but the magnitude of GCA was greater than SCA, indicating that
additive is more important than non-additive genetic variance in controlling the inheritance of NUE, NUPE, nitrogen
utilization efficiency (NUTE) and nitrogen harvest index (NHI) traits. The results indicated that under low-N and
high-N, the mean performance of a given parent is an indication of its general combining ability and the mean
performance of a given F2 cross is an indication of its specific combining ability effects for all studied NUE
components.
