The physiological basis of the genetic progress in yield potential of the Libyan bread wheat varieties Triticumaestivum L.

Abstract

A field experiment was conducted during 2017/2018 season at the experimental station of the Faculty of Agriculture, University of Tripoli. The aim was to determine the physiological basis of the genetic progress in yield potential of the Libyan bread wheat varieties since 1956. Twenty varieties of bread wheat Triticumaestivum L. released and introduced to Libya from 1950 to 2010 were used. Results showed that varieties of (Aboalkhair, Gaminia and Bohouth-304) produced the highest grain yield (511, 448 and 360 gm^-2) respectively, comparing to the other varieties. The main physiological component explaining yield potential was the above ground dry matter and not the harvest index. Results showed that grain number per squared area was the main yield component which correlated significantly with grain yield (R² = 0.73, P˂ 0.01), and this increase in grain number per squared area was mainly related to the number of spikes per squaredmeter(R² = 0.89, P˂ 0.01) and grain number per spike (R² = 0.69, P˂ 0.01). The Number of grains per spikelet and not the spike length was the main component which correlated significantly with the high number of grains per spike (R² = 0.79, P˂ 0.01). There was not any significant effect of either the spike length or number of fertile spikelets per spike on the number of grains per spike. Results showed that the increase in yield potential was not related to the date of release and introduction ofthe studied varieties to Libya. For instance, the variety Gaminia which was introduced to the country in 1975 produced higher grain yield than Bohouth-210 which was certified in 2005 (448 and 287 g/m^-2) respectively. However, there was an indication for grain weight as a quality character to be increased with year or release and introduction for the studied varieties. The importance of increasing yield potential of the Libyan bread wheat varieties through the increase of biological yield with the maintenance of the current harvest indices. In addition, improving the number of grains per spikelet through the different plant breeding programs as an important selection criterion is the most efficient path to increase the number of grains per square area.