Organizations such as the Canadian Wheat Board rely on yield forecasts to plan grain handling and marketing strategies. Therefore, a model that accurately predicts yield would be useful. In plant breeding programmes involving advanced line evaluations at different locations, lack of adequate resources may be a limitation. Differences among genotypes at different locations are due to genetic as well as environmental effects. These studies investigated the effects of temperature, photoperiod, and vernalization on the growth and development of spring wheat cultivars, and assessed the ability of the CERES-wheat model to predict yield in yield trials conducted in western Canada. Field experiments were conducted at Winnipeg and Carman, Manitoba, using three seeding dates at each location, to provide data for model calibration and validation. Controlled environment studies elucidated environmental effects which may be difficult to discern under field conditions. Da a on phenology, yield-related components, weather, and model-required soil properties were collected for all trials. High temperatures accelerated the growth of vernalization-insensitive cultivars by decreasing time to anthesis and time to maturity, and reduced the number of main stem leaves and yield-related components. High temperatures decelerated the growth of vernalizafion-sensitive cultivars and prolonged the length of the vegetative growth period. Differential cultivar phyllochron responses to temperature increases were evident. Therefore, the use of modified thermal time calculations in the CERES-wheat model may not be appropriate for all genotypes. To reduce errors in phyllochron interval calculations, crop modellers may need new equations to address temperature sensitivity of cultivars. Cultivar differences in time to heading, anthesis, and maturity, were attributable to differences in the time to terminal spikelet initiation. The CERES-wheat model was sensitive to changes in seeding date and locations.

Manipulation of Flowering presents the edited proceedings of the 45th University of Nottingham Easter School in Agricultural Science held at Sutton Bonington in England on April 7-10, 1986. This book is organized into eight sections. The first main section examines the measurement and prediction of flowering and analyzes how best to measure flowering when the aim is either to assist physiological interpretations or construct predictive models. The following sections explore juvenility, the nature of determination in meristems, vernalization, photoperiodic induction and flower evocation, and initiation and development to anthesis. Each of the main sections provides an analysis of the flowering problems and a critical view of how to achieve a better understanding and use of the physiology of flowering. This book will be of interest to crop researchers, plant physiologists, geneticists, and others interested in understanding flowering manipulation.