Abstract

The Northern Barley Improvement Program conducted a structured environment trial with Stage IV breeding lines at the southern Queensland site of Jondaryan over two seasons. The design included three sowing dates and three nitrogen rates, under irrigated conditions. The trial was analysed for agronomic as well as quality effects. Sowing date had the most significant effect (p > 0.05) on grain protein, friability, hot water extract (Institute of Brewing and European Brewery Convention methods) and diastatic power. Whereas grain size, Kolbach Index (KI) and malt alpha-amylase were significantly affected by genotype. One of the aims of this trial was to assess the malting potential of advanced breeding lines through the examination of malt with a range in KI levels. The results indicate that this type of trial provides useful information on both the agronomic and malt behaviour of elite lines. Variability in malt quality can be interpreted more easily when samples with a varying range in grain quality are analysed from a single site.

Introduction

Recent studies evaluating genotype and environmental effects have examined a range of malt quality traits and interactions between genotypes and sites. Overseas, a number of studies have investigated beta-glucanase, beta-glucan and hordein fractions (Molina-Cano et al. 1995; Swanston et al., 1995; Molina-Cano et al., 2000). In Australia, studies have reported genotype and environmental effects on malt quality including the key malt enzymes (Arends et al., 1994; Gibson et al. 1995), barley alpha-amylase subtilisin inhibitor (Jarrett et al. 1996) and Protein Z and Lipid Transfer Protein (Evans et al., 2000). For each of these studies the results demonstrated the variability between genotype and environmental interactions for specific commercial varieties. In addition, all studies evaluated barley samples with malting protein specifications. No recent research has been reported investigating the effect of environment and genotype interactions when evaluating malting performance of breeding lines, particularly evaluation of samples outside malting quality specifications.

The aim of this study was to use a controlled environment with a range of sowing dates and nitrogen applications to evaluate malt quality

Materials and Methods

Samples

Seven barley cultivars were obtained from 8 sites from the Stage IV advanced breeding trials (Northern Barley Improvement Program). The treatments were created from all possible combinations of three rates of applied Nitrogen (90 [N1], 120 [N2] and 150 [N3] kg/Ha) and three sowing dates (May 31^st [SD1], June 17^th [SD2] and July 13^th [SD3]).

Detailed grain and malt analysis and statistical was carried out as described in Fox et al. (2001)

Results and Discussion

Grain Quality

The effects of the treatments used in this field study had a significant effect (p < 0.001) on all grain size parameters measured (Table I). For plump grain (PG) and the > 2.8 fraction, both genotype and treatment had significant effects. In addition, for the > 2.8 fraction, the difference in grain sizes between the highest and lowest genotypes was much greater than for plump grain (Figure 1). Also the largest plump grain genotype (90S:202-33-2) had the highest percentage of > 2.8 fraction. While the smallest grain genotype (Camo*Koru 123) had the lowest > 2.8 mm fraction. These results suggest that using the > 2.8 fraction could be useful, in addition to the plump grain parameter, in selecting breeding lines for large grain characteristics.

Table I. Level of significance and percentage of effect for controlled environment trial

ns not sigifiicant, * p < 0.05, ** p < 0.001

Figure 1. Distribution of grain size fractions ten genotypes evaluated

For the two remaining grain quality characteristics measured, grain protein (GP) and thousand grain weight (TGW), treatment had a significant effect on both. While only TGW was effected by genotypes.

Malt Quality

Friability was significantly effected (p < 0.001) by genotype and treatment, although treatment had a much greater effect (Table II). Friability provides a physical measure of barley modification during malting and has previously been demonstrated as useful in evaluating malt modification (Altunkaya et al. 2001), particularly those characteristics that are controlled during malting, specifically beta-glucan. The results presented here support other data demonstrating the impact of genotype and environmental interactions on friability (Altunkaya et al. 2001).

Table II. Summary of quality data from controlled environment trial

The most important malt quality characteristic for selecting breeding lines is hot water extract. Under Australian brewing conditions, high temperature infusion mashing is common. Thus to select breeding lines with suitable extract levels, our program has focused on using an Institute of Brewing (IoB) style mash in selecting breeding material. The benefit of using such a mashing procedure was highlighted with this study. Extract measured using the IoB style (Fox and Henry 1992) showed significant differences between genotypes while the European Brewing Congress (EBC) mash did not show significant difference effect on genotypes. This highlights the difference between the two methods and demonstrates the value of selecting breeding lines for extract based on high temperature infusion mashes.

In regards to modification, genotype had a greater influence on KI than treatment although both were significant (p <0.05) (Table II). Although a number of treatment resulted in grain protein contents outside acceptable grain protein for malting, the data from this study provide valuable information on the modification potential of breeding lines. The factors used to derive KI, soluble nitrogen (SN) and total nitrogen (TN) were both significant for genotype and treatment. In the genotypes evaluated here, where KI was less than 40, the genotype generally had a low IoB extract. However, under EBC method conditions there was little variation between genotypes regardless of KI. Soluble nitrogen was more influenced by genotype. The variation between genotypes for SN could be explained by insufficient storage protein hydrolysis through the level in endoproteinase activity or substrate availability to endoproteinases (Osman et al. 2001). Alternative methods such as Hartong may provide more useful information as to the breakdown of protein matrix during malting.

Hydrolytic enzymes are responsible of the degradation of starch into fermentable sugars. Method to measure these enzymes include diastatic power (DP) and malt alpha-amylase (MAA). Genotype and treatment significantly effected the DP and AA measured evaluated in this study. However, treatment had a greater effect on DP than MAA. However, for malt alpha-amylase, genotype had a greater influence. These results support previous studies in Australia (Gibson et al. 1995; Arends et al. 1996) and overseas (Swanston et al. 1995; Molina-Cano et al. 2000a).

The impact of DP and MAA levels on extract was variable. Although there were differences between DP and MAA levels for genotypes, the differences did not impact directly on the EBC extract. However, under high temperature mashing conditions (IoB), it would appear only that genotypes with high MAA levels produced high IoB extracts. Little starch breakdown is required during malting so to achieve desirable level of extract with high temperature mashing, MAA levels in new varieties should remain high.

Conclusion

The use of a controlled environment trial to study the impact of sowing date and nitrogen fertilizer interaction with grain and malt quality has provided important preliminary information genotype performance. Specifically, the changes in extract and modification levels between genotypes subjected to varying level of nitrogen fertiliser and sowing dates have been highlighted. In addition, the benefit for breeding program in using methods that are similar to processing conditions increases the chances of selection lines suitable for Australian brewing conditions. Further analysis of multiple years of data from this structured trial will compare the benefits of a controlled environment over multiple site assessment of grain and malt quality.

Acknowledgements

The authors gratefully acknowledge the continuing support of GRDC for the Northern Barley Improvement Program.

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