investigation of changes in grain yield and some morphophysiological characteristics of wheat (triticum aestivum l.), maize (zea mays l.) and rice (oryza sativa l.) in recent decades in iran

twentieth century had faced considerable increase in crops yields. nonetheless, it is postulated that world population will reach 10.4 billion until 2050 which means the demand for agricultural crops production should be increased between 60 and 110 percent. in the present study, improvements in grain yields of wheat, maize and rice during the recent decades in iran were studies through analyzing morphological and agronomic data relevant to these three crops between 1957 and 2012. linear regression was used to analyze the trends of improvements in different traits. results indicated that wheat and maize grain yields in the target period have significantly increased, while little increase in rice yield was observed. results showed that breeding programs could significantly shorten plant height in wheat and maize, especially in spring wheat compared to winter wheat, but this was not the case in rice. regarding one thousand-grain weight, little change was observed in wheat although the amount of increase in this trait was more in spring rather than winter wheat. the study showed that newer maize cultivars were more tolerant to higher plant density compared to older cultivars. in rice, it was revealed that crop growing period has considerably decreased during the studied period. overall, it could be concluded that breeding could effectively increase spring and winter wheat and maize grain yields in iran. however, regarding rice it seems that breeding was not successful toward grain yield improvement.