بررسي روند تغييرات 50 ساله خصوصيات مرفولوژيك و فيزيولوژيك در برخي از گندمهاي ايراني

Physiological and morphological traits associated with genetic yield improvement of Iranian winter wheat cultivars released during past 50 years

In order to investigaten the physiological and morphological traits associated with 50 years winter wheat improvement in Iran, an experiment was conducted during 1998-1999 growing season in Mashhad, Iran. Six winter wheat cultivars that had been released during the past 50 years, were planted on a randomized complete block design. Each cultivar was planted under its own optimum planting density and nitrogen requirement. The results showed that the annual average increases in grain yield, total biomass yield and harvest index were 83 and 86 Kg/ha and 0.0037% respectively. Dry matter accumulation, radiation use efficiency and leaf area index after poll nation, nitrogen use efficiency and nitrogen uptake efficiency were higher in recent introduced cultivars compare to old cultivars. New wheat cultivars also had lower nitrogen harvest index to harvest index ratio and higher extinction coefficient than older cultivars. However older cultivars were taller and had longer internodes. Higher grain yield were positively correlated with higher number of fertile tiller and higher number of grain per m^2.