The genetic analysis of physiological traits in rice (Oryza sativa L.) contributing to aerobic adaption

Abstract

The adoption of non-flooded aerobic rice production in Australia would be advantageous to improve water productivity, however two varietal constraints are preventing its adoption. Firstly, current varieties are susceptible to cold temperatures at the early microspore stage (EMS) as deep-water is currently used as a thermal-buffer. Secondly, Australian varieties are not adapted to aerobic conditions. Furthermore, the expression of EMS cold tolerance under aerobic conditions is not well understood. This thesis examined genetic variation in traits and their contribution to aerobic adaption in rice. The objectives were to: 1) determine the expression of cold tolerance at EMS under aerobic conditions; 2) identify markers associated with quantitative trait loci for cold tolerance at EMS; and 3) determine whether early vigour could be used as an indirect selection method for aerobic adaption. Four glasshouse and seven field experiments were conducted. Firstly a set of 17 fixed genotypes were screened in a controlled temperature glasshouse under aerobic and flooded conditions to examine early vigour, and the consistency of cold tolerance between water regimes. The M205/3/M205//Millin/Lijiangheigu (2MML; 259 individuals, F6:7) population was phenotyped for cold tolerance at the EMS to identify associated markers. The 2MML population was then screened for EMS cold tolerance under aerobic and flooded conditions in controlled temperatures, and also in two field aerobic experiments located near Mackay. A further five yield experiments with the 2MML population examined genotype by environment interactions, and assessed any benefit of early vigour under aerobic conditions. Strong positive correlations existed between spikelet fertility obtained under flooded and aerobic conditions in 17 genotypes (rp=0.73**) and a subset of 52 2MML genotypes (rp=0.84**; rg=0.91) after exposure to cold temperatures (15/21.5°C) at EMS. Therefore, cold temperature screening may be conducted under flooded conditions, which is simpler to conduct, for cold tolerance under aerobic environment. Furthermore, strong genetic correlations existed for spikelet fertility between the glasshouse and the aerobic field screening in Mackay (rg=0.49-0.63). The broad-sense heritability was higher in the glasshouse (0.87-0.96 vs 0.53), demonstrating that selection in the glasshouse is more repeatable. Among 12 genotypes sampled for floral traits after cold exposure, spikelet fertility was correlated with the pollen number in anther, filled pollen on stigma, basal dehiscence Declaration by author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial ...