Performance and Stability of Some Durum Wheat Genotypes under Different Sowing Dates and Nitrogen Fertilizer Levels

The present study was carried out at Shandaweel Agricultural Research Station, Agricultural Research
Center, Egypt. Eight durum wheat genotypes of diverse origin were evaluated under 12 environments, which
are a combination between three sowing dates, i.e., 20th November, 10th December and 30th December under
two levels of nitrogen fertilizer, i.e., 50 and 75 kg N/fed during two winter growing seasons of 2015/2016 and
2016/2017. The combined analysis of variance revealed high significant differences among environments,
genotypes as well as genotype × environment interaction for six studied traits i.e., days to 50% heading, plant
height, number of spikes/m2, number of kernels/spike, 1000-kernel weight and grain yield/fed. The results
showed that sowing at the favorable date (20th November) using 75 kg/fed nitrogen fertilizer increased all
studied traits. The joint regression analysis of variance for the studied traits showed high significant mean
squares due to environment + genotype × environment interactions revealing that genotypes considerably
interacted with the environmental conditions. The mean squares due to G × E (linear) were found to be
significant for all studied traits, except for days to heading and 1000-kernel weight which reveals genetic
variability among genotypes for linear response to varying environments. Stability parameters (bi and S2d)
revealed that six genotypes were stable for days to heading, six for plant height, three for number of
spikes/m2, three for number of kernels/spike and six for 1000-kernel weight. Five out of the eight studied
genotypes, i.e., Sohag 5, line 2, line 3, line 4 and line 5 showed non-significant deviation from regression and
their regression coefficient values were close to unity which are classified as stable genotypes for grain yield.
Two genotypes had grain yield higher than the grand mean (Sohage 5 and Line 4) and could be considered the
most adapted genotypes.