Previous PageTable Of ContentsNext Page

Identification and characterisation of water limiting environments within Queensland wheat breeding trials

M. Cooper1, D.R. Woodruff2 and D.E. Byth3

1 Department of Agriculture, University of Queenslamd, St Lucia Q 4067
.Queensland Wheat Research Institute, P 0 Box 2282, Toowoomba Q 4350
Queensland Agricultural College, Lawes Q 4343

The objective of genotype selection in plant breeding trials is the identification of genotypes expressing improved adaptation to environments within a specified crop production system. The effectiveness of any selection experiment relies heavily upon the nature of gemotypediscrimination withim the environment and the relevance of the test environment to the crop production system. Therefore characterisation of breeding trial emvironments is am important component of interpreting and improving crop adaptation, defiming the envirommental challenge implicit within the breeding trial. This paper considers the use of three measurements, leaf water potential (LWP), osmotic potential (OP) and thermometer (IRT) air canopy temperature differentials, as techniques for assessing thewater status of wheat breeding trial environments in Queemsland.


Fifteen wheat genotypes were grown in four managed environments in which water availability was manipu.lated. Three environments were grown under rain.out shelters , low (LROS), medium (MROS) and high (HROS), and one was a fully irrigated (IRRIG) trial (Table 1). The rainout shelter plots were each four rows with 18 cm spacing by three metres, while the irrigated trial plots were four rows by 14 metres. All four trials were grown at Gatton, S E Qld during 1988. Between flag leaf emergence and anthesis LWP and OP measurements were taken on the flag leaf of each line in each environment. IRT readings were taken at flag leaf and a crop water stress imdex' (CWSI) was calculated. Environment means were calculated for each set of measurements and related to site mean grain yield and grain yield components.

Results and discussion

Water stress around anthesis is considered a major limitation to wheat grain yield in QId2. Identification of the presence and extent of water limitation around anthesis in breeding trials could provide useful information for investigation of the adaptation of wheat genotypes in breeding trial series. Severe water stress at anthesis was detected by each water stress measurement in two environments, LROS amd MROS. This was reflected in a reduction in grain number and graim size, reducing grain yield (Table 1). One environment, HROS experienced a mild water stress at anthesis but suffered no reduction in grain number or grain yield relative to the fully irrigated environmemt. The identification of presence or absence of anthesis water stress in this form of preliminary analysis provides a useful basis for investigatiom of genotype adaptation in these environments3. LWP, OP and IRT measurements wereeach useful in this environmental characterisation. The ease and speed with which the IRT could be used is a distinct advantage for characterising a large number of trials.

Table 1. Env. mean, grain yield, yield component and water status measurements for 15 genotypes in 4 envs

1. Idso S.B., Jackson R.D., Pinter P.J., Reginato R.J. and Hatfield J.L. (1981). Agr. Met. 24, 45.55

2. Woodruff D.R. and Tonks J. (1983). Aust J. Agric Res, 34, 1-11

3. Cooper M., Woodruff D.R. and Byth D.E. (1989). An investigation of the adaptation of selected CIMMYT wheat germplasm to water limiting environments in Queensland. This volume.

Previous PageTop Of PageNext Page