Genotypic Variations in Wheat for Phenology and Accumulative Heat Unit under Different Sowing Times

Abstract

Delay in wheat is perhaps the one of the major fact ors responsible for low crop yield mainly due to the sub-optimal temperature during th e different phenological stages. A field study was carried out to investigate the phenological perform ance of five newly developed wheat cultivars (Lasani-2008, Faisalabad-2008, Shafaq-2006, Sahar-2006 and Inqlab-91) under early (10-November) and the late sown (10-December) conditions during 2011-12 growing season. The experiment was laid out in randomized complete block design under factorial arrangement of treatments replicated four times. Results indicated that delay in sowing of wheat was detrimental for its growth. Early sown wheat got more number of days to attain different phenological stages, higher heat unit and heat use efficiency as compared to the late sowing. In c ase of late sowing, the cultivars phased a significant level of high temperature stress that a ffected the required days to crown root initiation, tillering, booting, heading, anthesis, grain fillin g and maturity of all cultivars as compared with ea rly sown crop. When wheat was sown late in season, the heat use efficiency was reduced in the range of 21-35% across different cultivars compared with ear ly sown crop. Variations were also apparent among cultivars regarding their response to sowing dates. The cultivar Faisalabad-2008 ontogenically being more plastic, performed well in late sown con ditions, nonetheless, cultivar Iqlab-91 remained superior to rest of cultivars, when planted early i n season. These results are of practical concern fo r wheat growers in Pakistan and may be fruitful in fu ture for crop modelling in wheat.