Comparison of winter habit and photoperiod sensitivity in delaying development in early-sown wheat at a site in New South Wales

Abstract

Summary. This study compared 2 mechanisms that delay the development of early-sown wheat, winter habit and sensitivity to photoperiod. To conduct this study, ear emergence dates were recorded for serial sowings of 15 wheats over 4 consecutive years at Temora, New South Wales, comprising 36 sowings in total. Ear emergence was measured as day of the year, and in both thermal and photothermal time from sowing.

The timing of ear emergence was first considered in 3 wheats that were insensitive to photoperiod and vernalisation. In contrast to thermal time, the duration from sowing to ear emergence did not vary with sowing time when measured in photothermal units. Such a measurement is essential for the study of mechanisms whose effect in delaying development is a function of sowing time. These results were obtained using a more simply calculated measure of photothermal time than has been previously reported.

For early-sown wheat, winter habit was found to more strongly delay ear emergence and provide greater flexibility in sowing time than responsiveness to photoperiod. Our study provided evidence that winter habit is a more attractive method of delaying ear emergence in early-sown wheat than photoperiod sensitivity. This finding supports the continued breeding of winter wheats for early sowings in the south-central wheat belt of New South Wales.