The tolerance of wheat to hight temperatures during reproductive growth. 2. Grain development

Abstract

A study was undertaken in the Canberra phytotron of the response of 66 cultivars of wheat to high temperature (30/25¦C) imposed throughout the period of grain development. The results from 20 Australian cultivars and their parental lines showed half of these to be clustered in the range where grain dry weight was reduced by 30-35% in response to high temperature when compared with 18/13¦C controls. The non-Australian lines were more normally distributed in their response to high temperature and included some cultivars that were less sensitive to high temperature than the best of the Australian lines. It was concluded that there is a need for a wider assessment of genetic variation if a response to high temperature is to be incorporated in a breeding programme. A more specific study on Kalyansona, one of the better cultivars under high temperature conditions and high radiation levels, failed to reveal a specific source of temperature insensitivity in the background of Kalyansona. A comparison of the response to high temperature during grain development of twoF1 hybrids with their parental lines (Banks, Kalyansona and Pinnacle) provided some evidence that traits such as high grain number per ear, large grains and low sensitivity to high temperature could be effectively combined to produce a high grain weight per ear under high temperature conditions.