Regression of Grain Yield of Maize Inbred Lines and Their Diallel Crosses on Elevated Levels of Soil-Nitrogen
A. M. M. Al-Naggar *
Department of Agronomy, Faculty of Agriculture, Cairo University, Giza, Egypt
R. Shabana
Department of Agronomy, Faculty of Agriculture, Cairo University, Giza, Egypt.
M. M. M. Atta
Department of Agronomy, Faculty of Agriculture, Cairo University, Giza, Egypt.
T. H. Al-Khalil Al-Khalil
Department of Agronomy, Faculty of Agriculture, Cairo University, Giza, Egypt.
*Author to whom correspondence should be addressed.
Abstract
Maize grain yield response to elevated levels of soil nitrogen is dependent upon genotype of the cultivar. Thus the optimum rate of N-fertilizer differs from maize genotype to another according to its nitrogen use efficiency (NUE). The main objective of this study was to determine the optimum N-rate for each studied inbred and hybrid that maximize grain yield. Six inbred lines of maize differing in their productivity under low-N were crossed in a diallel fashion to produce 15 F1ËŠs. Parents and F1ËŠs were evaluated in two seasons (2012 and 2013) using a split-plot design in randomized complete blocks arrangement with 3 replications. Main plots were allotted to four N-rates, i.e. 0, 80, 160 and 240 kg N/fed for N1, N2, N3 and N4, respectively. The sub-plots were assigned for the genotypes. Reducing N-level from 204 to 160, 80 and 0 kg N/feddan (fed) [one fed = 4200 m2] caused an increase in days to silking (DTS), anthesis silking interval (ASI), barren stalks (BS), economic NUEe and biological NUEb NUE and a decrease in the remaining studied traits including grain yield and its component. Maximum increase and decrease in traits occurred at N1 level (0 kg N/fed). The inbred lines L17, L18 and L53 proved to be tolerant (T), while L29, L54 and L55 inbred lines were sensitive (S) to N stress. The most tolerant crosses to low-N stress and the most responsive crosses to elevated levels of nitrogen were identified. Only two crosses (L18 × L53 and L18 × L55) showed high tolerance to low-N stress and responsiveness to high-N expressed in grain yield per plant (GYPP) and per fed (GYPF). The T×T group of crosses exhibited better performance in most studied traits than T×S and S×S groups of crosses under the low and high N levels. The three inbred lines L53, L18 and L17 and the three groups of crosses [inefficient responsive (IR), efficient non-responsive (ENR) and inefficient non-responsive (INR)] showed a quadratic response to the elevated levels of nitrogen with an optimum N level of 180 kg N/fed, while the three inbred lines L54, L29 and L55 and the efficient responsive (ER) group of crosses (L18 × L53 and L18 × L55) showed near linear response to elevated N levels.
Keywords: Zea mays, Low-N, tolerance, responsive, NUE, prolificacy, ASI