Genetic and Physiological Characterisation of Cotton Sodicity Tolerance
Project Leader: Shiming Liu
Key Researchers: Manasi Karmarkar, Zhonghua Chen (WSU), Michelle Mak (WSU) and Warwick Stiller
Brief Summary of Project Objectives:
After the discovery of low leaf sodium (Na) trait from Gossypium barbadense and its introgression into elite G. hirsutum backgrounds, this project aims to enhance understanding of underlying trait genetic and physiological mechanisms. The efforts also extend to the development of laboratory-based screening protocols for cotton sodicity tolerance and/or molecular markers applicable to future breeding as well as to demonstrate trait agronomic values in commercial farms.
Market/ end user:
Cotton growers, through the Cotton Breeding program and abiotic stress projects are the primary end users of this research.
Estimated year to uptake by end user:
Low leaf Na elite germplasm has already been used in our ongoing core breeding. The low cost and rapid screening tools from this project will accelerate the process of developing high performance cotton with improved sodicity tolerance adaptable to commercial production, however it will be up to 10 years until a variety may be released.
Executive Summary:
The ultimate objectives of this project are to identify and characterise the traits associated with cotton sodicity tolerance and to demonstrate the value to the industry.
Good progress has been made towards three of the four project milestones in the 2012/22 season.
The effort in developing laboratory-based screening protocols for cotton sodicity tolerance has resulted in the creation of sand, and sand-top soil base sodic media with a similar nature to sodic soils commonly observed in cotton regions, in terms of pH, electricity conductivity (EC) and exchangeable sodium percentage (ESP).
The candidate media identified were further used in screening experiments in the glasshouse that demonstrated their capability of differentiating the responses of test lines to sodicity treatment at seed germination and seedling stages in cotton. Despite this success, continuing efforts are required to improve screening reliability and repeatability through refining the media.
A recombinant inbred line population was tested in a replicated field experiment for the first time in the season. The population is derived from an interspecific cross between G. hirsutum and G. barbadense CSIRO bred varieties. During the season, genotyping for the population has been completed and the samples for tissue nutrient analysis and phenotyping of yield and fibre quality traits were collected and undergone the process. Field observations for plant morphology demonstrated the segregation and variation in the population for plant species types, leaf types and plant height, which provided an initial indication of the variability existing in the population, deeming it suitable for genetic studies and mapping for traits of interest.
The experiments to understand the agronomic values of low leaf Na trait in cotton were repeated at the non-sodic (Myall Vale) and sodic (Beloka, Wee Waa) sites. Leaf gas exchange parameters, biomass production, yield, nutrient uptake, and accumulation were measured in the experiments, and soil samples were collected twice during the season.Interestingly, soil sodic conditions did not impact dry matter production, nutrient accumulation, and seed cotton yield in the experiments this season, likely due to the high amount of in-crop rainfall. The leaf Na trait did modulate plant tissue Na statues, the lines with low Na trait, lower Na content in leaves were combined with higher Na in roots, and the oppose combination was observed for the lines with high leaf Na trait.
This evidence is consistent with the previous season results. Given lint yield data is still not available, K and P use efficiency was calculated according to estimated seed cotton yield. The results demonstrated low leaf Na trait enhanced P use efficiency in both sodic and non-sodic soils and could prevent rapid decline of K use efficiency from non-sodic to sodic soils as a contrast to high Na trait.The evidence confirms previous season’s results further proving low leaf Na trait’s value for cotton tolerance to sodicity as well as nutrient use efficiency.Future experiments will focus on validation, extension and enrichment of project scientific outcomes as well as development of new tools applicable to future breeding.
CSIRO Myall Vale Cotton Breeding Team