A Multi-Environment Trial Analysis of Frost Susceptibility in Wheat and Barley Under Australian Frost-Prone Field Conditions

Abstract

Low temperatures during the flowering period of cereals can lead to floret sterility, yield reduction, and economic losses in Australian crops. In order to breed for improved frost susceptibility, selection methods are urgently required to identify novel sources of frost tolerant germplasm. However, the presence of genotype by environment interactions (i.e. variety responses to a change in environment) is a major constraint to select the most appropriate varieties in any given target environment. An advanced method of analysis for multi-environment trials that includes factor analytic selection tools to summarize overall performance and stability to a specific trait across the environments could deliver useful information to guide growers and plant breeding programs in providing the most appropriate decision making-strategy. In this study, the updated selection tools approached in this multi-environment trials (MET) analysis have allowed variety comparisons with similar frost susceptibility but which have a different response to changes in the environment or vice versa. This MET analysis included a wide range of sowing dates grown at multiple locations from 2010 to 2019, respectively. These results, as far as we are aware, show for the first-time genotypic differences to frost damage through a MET analysis by phenotyping a vast number of accurate empirical measurements that reached in excess of 557,000 spikes. This has resulted in a substantial number of experimental units (10,317 and 5,563 in wheat and barley, respectively) across a wide range of sowing times grown at multiple locations from 2010 to 2019. Varieties with low frost overall performance (OP) and low frost stability (root mean square deviation -RMSD) were less frost susceptible, with performance more consistent across all environments, while varieties with low OP and high RMSD were adapted to specific environmental conditions.

Keywords: Hordeum vulgare L.; Triticum aestivum; factor analytic selection tool; genotype by environment interactions (GEI); interaction classes; spike fertility; spring radiation frost.

Figure 1

Accumulated rainfall, evapotranspiration (ET), daily maximum and minimum air temperature as a function of time from April to December between 2010 and 2019 growing seasons in SA, NSW and WA. Solid and dotted lines correspond to in-crop and long-term values [from 1960 up to the previous year for each frost expression experiments (FEE)] of accumulated ET (red color) and accumulated rainfall (blue color), respectively. Horizontal dotted black lines are temperature values at 30°C or 0°C. Values between parentheses represent rainfall deciles.

Figure 2

Heat map showing the occurrence of frost events expressed as a percentage of air temperature values falling from 2°C to −4°C from April to November across growing seasons in SA, NSW and WA regions.

Figure 3

Frost overall performance (OP, frost transformed values) as a function of frost stability for wheat (A–D) and barley (E–H). OP between different I-classes for wheat and barley are presented in panels (A-H), respectively. The I-classes are labeled with a three-character code (one for each factor), where each character is either “p” or “n” (for positive or negative loadings). For example, the I-class labeled “pnp” contains all experiments that had positive loadings in the first and third factors and negative loadings in the second factor. The FEEs within I-classes are presented in Table 6.

Figure 4

Frost overall performance (OP) between I-classes in wheat (panels A-F) and barley (panels G-L). The I-classes are labeled with a three-character code (one for each factor), where each character is either “p” or “n” (for positive or negative loadings). Colors correspond to difference in maturity type. The FEEs within I-classes are presented in Table 6 and Supplementary Figure 1.