ملخص
A field experiment was conducted during 2012/2013, 2013/2014 seasons at the experimental station of the Faculty of Agriculture, University of Tripoli. A set of eight Libyan six-rowed barley varieties were evaluated under full irrigation in order to identify the important selection criteria for yield and yield components. A randomized complete block design was implemented with three replications. Plot size was 2m long and 2m wide with ten rows, 20cm apart per plot. The seed density applied was 200 kg ha-2. The first fertilizer application regime was nitrogen (N) (50 kg N ha-1) and phosphorous (P) (64 kg P ha-1) applied as di-ammonium phosphate (DAP) at sowing. The second fertilizer application of nitrogen (100 kg N ha-1) as ammonium nitrate was added at the time of stem elongation. Other agronomic practices (irrigation, weed control, etc.) were carried out when needed. At harvest, 0.2 m-2 and then 1.0 m-2 were sampled per plot and the following measurements were taken: above-ground dry matter m-2, grain weight m-2, plants m-2, spikes m-2, grains m-2, grains spike-1, thousand grain weight, plant height, peduncle length, and spike length. The results showed that there were no statistically significant differences between the varieties in most studied traits. However, the results obtained showed significant differences in grains spike-1 trait (P = 0.05). It was concluded that varieties with a low number of grains per spike compensated this lack by producing heavier grains. Consequently, yield potential was statistically similar to this set of varieties. In addition, the results showed that the grain yield is primarily attributed to the increase in the above-ground dry matter and not to the harvest index. Thus, using biomass as a selection criterion is a preferred direction when breeding for high yield potential under favorable conditions