Breeding cotton for a variable rainfall environment 18th Australian Cotton Conference, Broadbeach, QLD Warren Conaty, David Johnston, Alan Thompson, Susan Jaconis, and Greg Constable August 11th 2016 CSIRO agriculture AND FOOD

CSIRO rainfed breeding program Parental Selection F2& F3 Evaluations F4 Single Plant Selection Initial Evaluations (Narrabri) Progeny Rows Intermediate Preliminary Offsite Preliminary Onsite Advanced Material onsite location (Narrabri) Up to 5 offsite locations Managed water stress to improve rainfed breeding | Warren Conaty

Australian rainfall patterns Highly variable rainfall Summer dominant Average 650mm In-crop 350mm Skewed Figure 1. (a) Frequency of in-crop rainfall and (b) variability in monthly in-crop rainfall for Narrabri. Managed water stress to improve rainfed breeding | Warren Conaty

The problem One-in-five years has low yield (<550 kg ha-1) and has no statistical difference between genotypes i.e. we cannot reliably select superior lines. Historically, to manage the risk of rainfall variability the CSIRO rainfed breeding program has: selected for indeterminate cultivars; utilised skip-row configurations; reduced nitrogen inputs, and; pre-irrigated rainfed evaluations to simulate a full soil water profile. However: One-in-five years has low yield (<550 kg ha-1) and has no statistical difference between genotypes - i.e. we cannot reliably select superior lines. Managed water stress to improve rainfed breeding | Warren Conaty

Hypothesis Application of a single furrow irrigation in dry years will increase trial yields above the threshold of statistical genotypic resolution Managed water stress to improve rainfed breeding | Warren Conaty

Aims To determine if and when a single irrigation could be applied to rainfed evaluations when yield is expected to fall below the confidence threshold (Crop Modeling) To assess the stability of germplasm performance under both rainfed conditions and limited water situations (Field Trials) clarify if germplasm selected under rainfed conditions can produce high lint yields in seasons with higher than average rainfall. Managed water stress to improve rainfed breeding | Warren Conaty

Development of: Managed stress system (MSS) Result: An irrigation should be applied to a ‘rainfed’ experiment when soil water deficit reached 90-100mm by 100-110 DAS Managed water stress to improve rainfed breeding | Warren Conaty

Field Validation: MSS Three seasons Figure 4. Soil water deficit for each season in Rainfed and MSS treatment Three seasons 21 genotypes grown under rainfed and managed stress Soil water deficit measured via neutron attenuation Yield analysis Managed water stress to improve rainfed breeding | Warren Conaty

MSS Validation- Results Rainfed Sowing year Treatment Rainfall (mm) Avg. trial yield (kg ha-1) Genotype p-value Co-efficient of variation (%) Treatment x genotype 2013 Rainfed 127 546 0.329 16.4 0.726 MSS 1121 0.008 9.9 2014 199 785 0.002 11.0 0.020 1324 0.004 7.8 2015 350 823 <0.001 14.1 n/a Managed water stress to improve rainfed breeding | Warren Conaty

Interactions Genotype rankings differed significantly between rainfed and MSS in 2014/2015. different rainfall and crop fruit setting pattern. driven by low and medium yielding genotypes high yielding genotypes are consistent interaction is no longer significant when looking at multiple years Genotype rankings under MSS were different to rainfed in 2014/15. Due to effect of different rainfall pattern on genotypes with different crop setting pattern. Genotype rankings differed significantly between rainfed and MSS. This interaction was driven by low and medium yielding genotypes. Thus selection for yield under MSS would not necessarily omit the best yielders from rainfed in dry seasons. More seasons of testing are required to evaluate this interaction. Figure 5. Rainfed and MSS rankings for lint yields (2013/2014 and 2014/2015). Managed water stress to improve rainfed breeding | Warren Conaty

Main Conclusions Developed a managed stress system that optimized a single irrigation to meet yield threshold Irrigating the MSS was necessary to resolve genotype differences in 2013/14 When rainfed yields increase due to rainfall, the MSS was not necessary to resolve genotype differences MSS Rainfed Managed water stress to improve rainfed breeding | Warren Conaty

What does this mean for our breeding program? Using the MSS, we are able to get useful data in years when yields would be too low to evaluate genotypes Since grower income is greater under better environments than very limited water situations, genotype performance under MSS may actually identify better and more realistic long term options for growers. Best performing genotypes under rainfed conditions in dry seasons will also be captured. Rainfed genotype evaluation is repeated over multiple seasons and sites and genotype selection is based on all sites, not just MSS. Rainfed genotype evaluation is repeated over multiple seasons and sites and genotype selection is based on all sites, not just MSS. Thus best performers under rainfed conditions in dry seasons will not be missed. Note however that since grower income is greater under better environments than very limited water situations, genotype performance under MSS may actually identify better long term options for growers. Managed water stress to improve rainfed breeding | Warren Conaty

CSIRO rainfed breeding program Parental Selection F2& F3 Evaluations F4 Single Plant Selection Initial Evaluations (Narrabri) Progeny Rows Intermediate Preliminary Offsite Preliminary Onsite Advanced Material MSS onsite location (Narrabri) 5 offsite locations Managed water stress to improve rainfed breeding | Warren Conaty

Thank you Thank you to the technical staff of CSIRO cotton breeding group, particularly Mark Laird, Mick Price, Adam Suckling, Megan Cameron, Deon Cameron, Jo Price and Kellie Cooper for their invaluable contribution to this work. CSIRO cotton breeding is undertaken in the Cotton Breeding Australia joint venture between CSIRO and Cotton Seed Distributors. CSRIO AGRICULTURE AND FOOD Dr Warren Conaty Research Scientist Warren.Conaty@csiro.au CSIRO AGRICULTURE AND FOOD