the relationship between timing and duration of phenological events and grain yield in iranian wheat cultivars

abstract in order to study of relationship between timing and duration of phenological events and grain yield of wheat plants, an experiment was performed at moghan college of agriculture and natural resources-university of mohaghegh ardabili research farm during 2010-2011. the plant materials (81 wheat cultivars) were evaluated using a simple lattice design with two replications under irrigated condition. dates of various phenological events were recorded based on growing degree day (gdd). the results showed that modern wheat cultivars generally produced more grain yield and harvest index than old cultivars. more grain yield in modern cultivars associated with more grain number per unit area. no significant differences were observed between modern and old cultivars with respect to biological yield and 1000-grain weight. the cultivars analyzed exhibited a large degree of variations in the dates of stem elongation, booting, heading, anthesis and physiological maturity. in the present study, no apparent relationships were found among grain yield and that of the time to stem elongation, anthesis and stem elongation-anthesis phase. grain yield was significantly correlated with grain filling period (anthesis-physiological maturity phase), showing that a longer duration of this phase could increase grain yield in the region