Abiotic Stress II

Project Leader: Warren Conaty
Key Researchers: Katie Broughton
Brief Summary of Project Objectives: The aim of this project is two-fold:

  1. Identify genetic diversity in the limiting transpiration trait (TRLim VPD)and evaluate the suitability of this trait to cotton production environments/systems, and; 
  2. Investigate the genetic diversity and impact of high temperature stress on floral reproduction. 
Although this research has taken a more fundamental approach than the Abiotic Stress I project, the ultimate application of this work is still to identify abiotic stress resistance traits for application in the CSIRO cotton breeding program.

Executive Summary

In the first year of the project significant work has been undertaken to address the research milestones of this project. Germplasm has been screened for the presence of the TRLim VPD trait, with diverse responses in transpiration as a function of VPD observed. An initial study of the effect that this trait has in two genotypes was conducted, uncovering that the TRLim VPD trait provides a yield benefit in scenarios where VPD is high. Importantly, access to soil water is still required for this yield advantage to be achieved. This is logical as without access to some water the crop cannot grow and produce yield. Further work needs to be conducted to further pinpoint the scenarios where this trait is beneficial, and why. This may include the characterisation of environments (e.g. terminal drought vs. episodic drought associated with summer rainfall events) and the degree to which transpiration is limited to conserves water for use during reproductive growth. Further studies will also aim to identify secondary physiological, morphological and biochemical traits associated with the TRLim VPD trait.
Significant progress has also been made on the reproductive heat tolerance portion of the project. Field studies have identified genetic variation in pollen viability, as determined via a triphenyl tetrazolium chloride based cellular viability assay. A detailed glasshouse study has also been conducted. This study aimed to independently test the effect of temperature on pollen viability and subsequent fruit retention and boll components. While the viability of pollen samples has not yet been analysed, this study has shown that genotype differences in fruit retention occur. Once pollen viability data is finalised, we will be able to definitively determine whether genotype differences in pollen viability have an influence on ovule fertilisation and fruit retention. This knowledge will provide the final piece in the puzzle to determine if genotypes expressing higher pollen viabilities confer an increase in fruit retention at high temperatures.
Recent Project Research Achievements

  • Genetic variation to the TRLim VPD trait has been identified.
  • Preliminary studies show that the TRLim VPD trait provides a competitive yield advantage in scenarios where high VPD is observed, and where water is available for the crop to grow and produce yield.
  • Genetic variation in pollen viability has been observed using a triphenyl tetrazolium chloride (TTC) based cell viability assay
  • A glasshouse experiment has isolated the effect of pollen viability on fruit retention, future work will link this effect to pollen viability as measured by the TTC cell viability assay.