investigation of barely grain yield improvement during the last half century across golestan province

introduction barely (hordeum vulgare) is the fourth most important cereal after wheat, corn and rice. regarding the role of breeding to increase barley grain yield a large number of studies have been done in different countries. however, a few studies have been performed across golestan province, in iran. therefore, this study was conducted to know what barley traits have changed with grain yield during recent years. how these traits will further improve the barley grain yield in the future breeding programs? materials and methods in order to study barely grain yield improvement during the last half century across golestan province, this expriment carried out at randomized complete block desing with 4 replications in gonbad kavous university research field in 2013-2014. treatments were included nine barley cultivars: sahra, dasht, torkaman, gorgan4, nimruz, mahoor, khoram, reyhan and yousef. we analysed the results using anova in the statistical software package sas. step by step regression analysis and pathway analysis was done to evaluate the relative proportion of different traits on yield and direct and indirect impacts of yield components on grain yield, respectively. results and discussion the results showed that the values of the studied parameters were significantly different in different cultivars. results illustrated that the hieghest and the lowest grain weight were related to mahoor (37.33 mg) and torkaman (22.66 mg), respectively. due to the high number of rows per spike in barely cultivars, grains are closer together and there are less space for growth and phothosynthetic material storage. in addition, total assimilation was not enough to fill the grain of cultivars which have the more grain numbers per spike and it caused low grain weight. although thousand grain weight is among the main grain yield components with high heritability, it influenced by other components such as the number of spikes and its length. the highest and the lowest grain number per spike were related to torkaman and mahoor cultivar, respectively. mahoor and yousef had the hieghest and the lowest spike numbers per square meter, respectively. six-row cultivars had more number of grians per spike compare with two- rows cultivars due to more rows per spike. yousef cultivar with 1529.7 gr.m-2 had the highest biological yield and reyhan had the lowest biological yield with 1155.7 gr.m-2. results indicated that biological yield was increased during released years. if carbon produced during photosynthesis, allocate on economic parts or grains, rising of biological yield would be an effective parameter. in other words, barely cultivars with high biological yield and harvest index, would be likely to have a high grain yield. the highest and the lowest of grain yield with 388.33 gr.m-2 and 243.33 gr.m-2 were obtained at yousef and torkaman cultivar, respectively. the results indicated that the potential of grian yield is different among various barely cultivars. results revealed that new cultivars had high grain yield. the highest and the lowest of harvest index with 32.66% and 20.33% were observed at sahra and torkaman, respectively. it seems that new cultivars allocate more phothosysnthetic material to grains. path way analysis showed that thusand grain weights, the number of grians per spike and the number of spikes per square meters had direct effects on grain yield, respectively. furthemore, among these three factors, the number of grains per spike had the highest direct effect on grain yield. the indirect effect of thousand grian weights on grain yield through number grains per spike was high and negative. moreover, correlation results showed that these two traits had negative effect together. conclusions in summary, the results suggested that the highest yields were related to new cultivars and harvest index was increased during released years of cultivars. new cultivars had higher grain yield than the old cultivars. in addition, path analysis results showed that the number of grains per spike had a major effect on grain yield.