student profile: Mr Yoav Yichie


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Thesis work

Thesis title: Mechanisms of salt tolerance in the Australian wild rice species

Supervisors: Brian ATWELL, Thomas ROBERTS

Thesis abstract:

Salinity affects a substantial and growing proportion of arable land globally and is particularly detrimental for irrigated cropping, which provides approximately one-third of the world’s food supply. Millions of hectares in the humid regions of South and Southeast Asia are otherwise suited for rice production but are left uncultivated, or give very low yields, because of soil salinity. With ongoing climate change, ocean surges are posing an increasing threat to low-lying rice cultivation. Cultivated rice (Oryza sativa), the most important food crop in Asia much of the pantropical zone, is a highly salt-sensitive species. Creating salt-tolerant cultivars of rice is thus an international priority, especially in SE and southern Asia where rice is the major food crop.

Wild crop relatives are an effective approach to provide improved traits of commercial varieties. While there continues to be a strong emphasis on employing resistance genes for pests and diseases (biotic stresses), a range of genes for abiotic stress resistance are now being introduced to various types of vegetables, cereals, pulses and other crops. The genetic pool within the two cultivated rice species is small relative to the genetic pool within the 22 wild species of the Oryza genus as a whole. Some of these wild Oryza species are endemic to the north of Australia and have therefore adapted to resist a range of abiotic stresses including heat, drought and salt stress.

My research focuses on the vast genetic diversity of endemic Australian rice species, particularly O. australiensis and O. meridionalis. There is now a burgeoning interest in these species as a source of abiotic stress tolerance genes, but so far no work has been published on their salt tolerance.
Two rounds of physiological experiments at Macquarie University revealed significant differences in relative growth, biomass and overall performance of several wild Australian rice accessions grown under saline conditions, even compared with the salt-tolerant O. sativa landrace Pokkali. The results strongly suggest that salt tolerance was peculiar to the ecotypes from saline landscapes.

Building on this work, in early 2017 I conducted a high-throughput, glasshouse-based, salt-tolerance phenotype screening experiment at The Plant Accelerator, a national phenomics facility in the University of Adelaide, using Australian wild rice species and known salt-tolerant cultivars of O. sativa. The large datasets obtained, comprising non-destructive measurements of plant growth and function, enabled me to elucidate dynamic responses of rice growth and morphology in response to salinity. The experiment validated my previous findings by identifying the same salt tolerant ecotypes.

In 2018, I have been working to reveal the mechanisms that underlie the salt tolerance of the wild rice accessions using state-of-the-art proteomics experiments. The preliminary results show differential expression of several proteins of interest in the salt-tolerant accession compared with the sensitive one. More broadly, this work represents my contribution to addressing the phenotyping bottleneck that is restricting the flow-through of genomics advances into improvements in crop performance.

I have also been constructing a mapping population to enable a genetic analysis of the salt tolerance trait by crossing salt tolerant accession with salt sensitive. The goal is to use F2 mapping population in order to discover key quantitative trait loci (QTL)/gene(s) that characterise these tolerant ecotypes by using a tailored Chip-SNP database.

My project outcomes are an entirely novel approach to addressing the problem of salt sensitivity in rice by utilising the genetic diversity in the Australian wild rice germplasm; this has the potential to strengthen food security because rice is such a vital crop in world terms. My findings will be utilised in breeding programs to generate novel rice cultivars for farmers in salt-affected lands, using local recipient genotypes enhanced with Australian wild rice gene(s).

Note: This profile is for a student at the University of Sydney. Views presented here are not necessarily those of the University.