Dr David Collings1, Ms Maketalena Aleamotu’a1, Dr Harsh Raman2, Dr David McCurdy1

1The University of Newcastle, Callaghan, Australia,
2NSW Department of Primary Industries, Wagga Wagga, Australia\

Phi thickenings are single bands of secondary cell wall formed within the apex of the developing root in many species, particularly in Brassica. While their function(s) remain unknown, we speculate that they stiffen the root tip, aiding in soil penetration, thus representing a potentially important agricultural trait. Our aims are to determine the molecular pathways leading to thickening development, and subsequently to determine their functions. We have previously demonstrated that different Brassica cultivars vary in their ability to form phi thickening in response to salt and the stress hormone jasmonic acid (JA). In this project, we use this variability to characterise the molecular development of thickenings.

We initiated a genome wide association study (GWAS) using more than 200 lines from the BnAssyst diversity panel by phenotyping phi thickening induction in response to salt or JA. Strong variability was detected: some lines induced strongly with both stimuli while some formed no thickenings, and others responded to only one stimulus. We have also assessed several Brassica breeding populations, identifying crosses in which parental lines showed different phi thickening induction responses. In one Brassica rapa cross, for example, the segregtation of two separate phenotypes in the F2 progeny is consistent with the presence of multiple genetic differences in both JA signalling and late in the phi thickening developmental pathway. Data from both analyses are currently being processed to determine genetic loci associated with phi thickening induction, an outcome directly applicable to crop breeding strategies in Brassica and other crops where phi thickenings occur.


A plant cell and molecular biologist interested in root growth and development, from the biophysical through to the cellular level.



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