Summary

Traditionally based in southern New South Wales, the Australian rice production system can suffer from severe yield reductions due to cold damage at any time. To reduce potential damage to rice crops farmers raise the standing water level after panicle initiation to protect young developing inflorescences. With increasing irrigation costs and water limitations to rice crops, varieties adapted to cold tolerance would reduce the need for this practise and hence the cost, while stabilising water productivity. The proposed project will evaluate variation and elucidate the underlying mechanisms in key physiological traits and molecular quantitative trait loci (QTLs) that may contribute to cold tolerance. Ye et al. (2009) grouped varieties into those that had a ‘general’ cold tolerance unrelated to reproductive organ structures, and those that had ‘specific’ or reproductive cold tolerance. This project will aim to differentiate between physiological mechanisms involved in vegetative and reproductive cold tolerance mechanisms using a large number of lines from a number of populations. Initially we will utilise the Reiziq x Lijiangheigu population (Ye et al. 2010) which is available for immediate use, and additional populations relevant to cold tolerance are currently being generated in the rice breeding program. Screening will be conducted at both vegetative and reproductive stages, the latter focusing on key components of floral architecture including basal dehiscence length, stigma area and their associations with spikelet fertility. Identified trait/QTLs will then be available for incorporation into the breeding program to maximize productivity of rice adapted to southern Australian production areas.

Program

Rice

Research Organisation

The University of Queensland

Objective Summary

The major objective of the project will be to improve understanding of cold tolerance in terms of underlying physiological mechanisms and the molecular basis (genomics) of traits involved in the maintenance of cold tolerance. We will expand on the work of Ye et al. (2009) which distinguished between ‘general’ cold tolerance unrelated to reproductive organ structures, and those that had ‘specific’ or reproductive cold tolerance, to try and identify mechanisms and associated QTLs. Aside from vegetative screenings, the proposed project will investigate floral architecture in the genetic material available. Recently basal dehiscence length has been identified as a mechanism contributing to improved production under high temperature, and this mechanism is also likely to contribute positively to cold tolerance, and will be investigated. The project will aim to identify a floral characteristic ‘ideotype’ for cold (and concurrently heat) tolerance for rice under current temperate production methods (ie – high nitrogen and plant populations). Our understanding may be further improved by the imposition of a number of treatments for example the role of nitrogen and its negative effect on cold tolerance of rice floral development and fertilisation, and these may also be investigated. This project will aim to differentiate between physiological mechanisms and QTLs involved in vegetative and reproductive cold tolerance mechanisms using sets of recombinant inbred lines (RILs) generated from crosses using cold tolerance donors from diverse genetic background and current temperate rice varieties.