Differences in yield physiology in wheat cultivars grown under frost-prone field conditions in Southern Australia

Abstract

Low temperatures during the flowering period of cereals can lead to floret sterility and subsequent yield reduction. In this study we aimed to understand the physiological bases of yield determination among wheat genotypes grown under frost conditions in southern Australia. One experiment was carried out at Mintaro in South Australia in 2016. Treatments consisted of five wheat cultivars and a synthetic-derived wheat line sown at two different times of sowing (TOS) under field conditions. Yield and yield components were analysed at maturity. To analyse in more detail changes in grain number m-2 in response to frost, we mapped the distribution of grains within the spike. The trial experienced early frosts that mostly affected TOS 1, as a result the grain yield of TOS 2 was 3-fold higher than TOS 1. Sterility varied depending on TOS, cultivars and their interactions. For example, the later maturing variety ‘Yitpi’, which in part avoided the early frost, had the lowest level of sterility in contrast to the earlier maturing varieties such as ‘Scout’, ‘Wyalkatchem’ and ‘Mace’ which showed up to 100% sterility in TOS 1. In addition, we showed a clear trend to increase the number of spikelets exhibiting a significant difference in fertility between TOS. Therefore, optimising flowering time to minimise frost exposure is amongst the most important strategies to minimise frost damage while managing heat and drought stress.