The main objective of this investigation was to determine the
importance of genotype X nitrogen fertilizer interactions and
reciprocal effects in evaluating corn populations for use in
breeding programs. Eight parental single crosses, 28 arid
their reciprocals were evaluated an two adjacent experiments under
two nitrogen fertilizer levels (60 Kg N/f addan — low level and 120
Kg N/f addan — high level). Datم were recorded on grain
yaeld/plcint. number of kernels/row, number of rows/ear, loo
kernels weight, ear height. silking and tasseling dates. Mean
squares of nitrogen level was significant for all traits; except
for loo kernels weight and ear height. Increasing nitrogen level
increased the mean values of all traits.Signjfjcant. genotypes mean
squares were detected for all traits except for ear height. Except
for no. of rows/ear and 100 kernel weight, there were genotype by
nitrogen level interactions. Only under the low nitrogen level
there were detectable significant differences among genotypes and
their reciprocals for grain yield per plant. Data of mean
performance and heteroeje for grain yield/plant showed wide
differences of reciprocal effects in certain crosses in eac1
nitrogen level and in combined analysis. Most heterotic effect
values were higher- under the high nitrogen level. The highest
amount of heterotic effects (more than 15 %) were obtained from
the some studied double crosses based on the combined analysis.
Combined data of GCA mean squares showed significant differences
for all traite expcet for number of row/ear, 100 kernels weight
؟md ear height and they were higher under the high nitrogen level
in most cases. GCA played the major role in the inheritance of
most traits and exhibited a greater degree of interactions with
nitroqen level than SCA. The parenntal single crosses 4, 5 and 8
had the highest GCA effects for yield/plant and some of its
components. Data revealed significant differences for specific
combining ability (SCA) for gr-am yield/plant, number of
kernels/row and number of rows/ear. In most cases, unstable trend
of SCA effect was observed from one nitrogen level to another. For
grain yield/plant, ten out of twenty eight double crosses
exhibited signiricant desirable and positive SCA . effects. |
