Response of spring type wheat (Triticum aestivum L.) cultivars to different chilling treatments

Late sowing of wheat in autumn due to environmental conditions or late harvesting of cotton crop results in substantial yield loss. It may be attributed to non-fulfillment of chilling requirements. The present study was conducted to identify the chilling requirement of autumn sown cultivars of wheat. Effect of chilling treatment (measured in vernalization days (VDs)) on seven wheat cultivars (five Pakistani and two American) was observed by exposing the seedlings to 6 degrees C for 7, 14, 21, 28 and 35 days that is 6.72, 13.44, 20.16, 26.86 and 33.60 VDs. Seedlings which acted as control were not subjected to chilling treatment. All spring type wheat cultivars headed irrespective of their chilling treatment but increase in VDs, enhanced days to heading. Winter type wheat "Caldwell" did not show heading which indicated its high VDs requirement. Chilling treatment also affected grain yield of all cultivars. Sehar-06 and Marquillo demonstrated highest yields at 6.72 VDs while GA-02, Inqilab-91, Chakwal-50 and Freed-06 manifested highest yields at 13.44 VDs. The results of the experiment revealed that heading time and grain yield of all spring type wheat cultivars is affected by chilling treatments. Depending upon the response of the cultivars and available VDs calculated from temperature data of last 20 years. It is suggested that GA-02, Inqilab-91, Chakwal-50 and Fareed-06 must be sown in mid December while Sehar-06 can be sown in the start of January to meet their chilling requirement under field conditions without substantial yield reduction.