M. Jahani Doghozlou - Department of Plant Production and Genetics, School of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.
Y. Emam - Department of Plant Production and Genetics, School of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.

Wheat floret primordia develop in a rather narrow window of time, mostly coinciding with stem elongation. That is why the stem elongation phase is considerd a critical period for grain number and yield determination. Under controlled conditions, floral primordia development of ۱۰ mostly adopted bread wheat cultivars including Bayat, Azadi, Falat, Navid, Chamran, Marvdasht, Pishtaz, Shiraz, Sirvan, and Baharan, which were released during the last five decades, was studied in detail at Shiraz University, Shiraz, Iran. Floral primordia monitoring showed that visible floral degradation among wheat cultivars occurred at several floral developmental stages from green anther (GA) to anthesis (AN). Floral degradation period started from yellow anther stage and was longer in cultivars with lower grain number per spike (Bayat, Navid, Shiraz and Azadi cultivars). Also, cultivars that started stem elongation earlier, such as Sirvan, Baharan, Chamran, and Falat, had extended period for stem elongation and produced higher grain number per spike. Overall, it appeared that under short growing seasons of semi-arid regions, in which delay in flowering usually results in more floral mortality during GA to AN, cultivars with earlier stem elongation could be more efficient in production of grains.

Floral degradation, Floret primordia number, Floral score, Triticum aestivum L.