RELATIONSHIPS AND CORRELATIONS BETWEEN BREWERY TRAITS OF THE SPRING BARLEY VARIETIES

Andrzej Bichoński, Tadeusz Śmiałowski

ABSTRACT

Interrelationships between fine grid extract (as a dependent trait – X) and 6 independent traits (Y₁, Y₂…Y₆): grain filling, malt protein, malt fragility, wort viscosity, diastatic power and fermentability were examined. The material for investigation was 235 varieties and strains of brewery spring barley examined in preliminary and secondary trials in 1999-2001.

Key words: path coefficient analysis, bewaring quality, brewery spring barely, traits..

INTRODUCTION

High quality of brewery spring barley used for malting and then brewing beer [2, 11, 13] requires from the brewers the observation of very strict norms of grain quality. Therefore, the evaluation of brewing quality of breeding materials of brewery spring barley is made on the basis of detailed analyses of technological traits of grain, of which the most important brewing quality indicator is fine grid extract, and then: grain filling, malt protein, malt fragility, wort viscosity, diastatic power and fermentability [1, 6, 11]. The traits of brewing quality remain strictly correlated with each other; and disruption of this correlation in the breeding process might deteriorate quality norms, and thus deprives the cultivated barley of brewery qualities [1, 22, 23].

The investigation conducted [23] indicate that technological traits are strongly genetically determined and, to a large extent, hereditary [25], but their effects on the final brewing quality is not uniform [16]. Other studies [2, 3] indicated highly significant phenotype and genotype correlations between the traits of brewing quality of barley. It must be supposed that there are also strong cause-and-effect correlations between these traits. One of the methods of determination of the traits which are biologically correlated is path coefficient analysis of the coefficients of phenotype and genotype correlations [4, 5, 7, 8, 10, 15, 20].

A measurement of this correlation is the direct and indirect effects of influence of the examined traits calculated with the method of path coefficient analysis. In our research this is the evaluation of the common relation and of the influence of 6 variable traits (explanatory – independent or causality) grain filling (Y₁), malt protein (Y₂), malt fragility (Y₃), wort viscosity (Y₄), diastatic power (Y₅), fermentability (Y₆) on the explained trait (dependent of effective); fine grid extract (X). With the application of path coefficient analysis, based on the coefficients of genetic correlation calculated between the above-named technological traits of varieties and strains of brewery spring barley in 1996-1998 in the barley collection and first and second preliminary trials, Śmiałowski et al. [21] determined strong cause-and-effect correlations between the traits of brewing quality. As the obtained results explained t he correlations between the traits with older objects, the aim of the present work was to determine the correlation between selected traits of brewing quality with brewery barley based on the newest materials examined in first and second preliminary trials in 1999-2001.

MATERIALS AND METHODS

The research material was model 349 strains and 3 varieties: Rudzik, Stratus and Scarlet of brewery spring barley evaluated in first and second preliminary trials in 1999-2001. Altogether, during 3 years, in the first preliminary trials 249 objects were examined and in the second preliminary – 104 objects. In a laboratory, the analyses of 10 traits were performed; 1000 kernel weight, grain filling, protein content in malt, soluble protein, Kolbach index, fine grid extract, malt fragility, wort viscosity, diastatic power and fermentability.

Phenotype and genotype correlations between these traits were examined with the application of the FEGEKOR 3 (TP) computer program worked out by Professor Węgrzyn in Zakład Roślin Zbożowych (Grain Plant Institute) of IHAR (Plant Breeding and Acclimatization Institute). The obtained results were described in the work of Bichoński et al. [3].

For the performance of path coefficient analysis, the method described by Dewey and Lu (1959) was applied. According to the assumption, the coefficient of genotype correlations between fine grid extract (as the explained traits – dependent or effective (X) and 6 explaining traits – independent or causality (Y₁, Y₂…Y₆) i.e.: grain filling, malt protein, malt fragility, wort viscosity, diastatic power and fermentability. The cause-and-effect relationships and correlations between the examined traits were presented on the path diagram (Fig.1) in a form of arrows directed from the explaining variables (cause) to explained (effect).

Table 1 presents the results of laboratory analyses and variability coefficient for 7 technological traits: grain filling, malt protein, malt fragility, wort viscosity, diastatic power, fermentability and fine grid extract. Equalised breeding material was determined as well as nearing variability coefficient in both series of experiments (Table 1). Strong equalisation of barley strains with respect to brewing quality means strict observation of very high quality norms during particular breeding stages.

Among 7 examined technological traits, the most important one determining a high level of brewing quality of grain was the content of fine grain extract. This trait is connected with other traits of brewing quality [3, 11, 16, 22, 23]. In relation to this, the cause-and-effect analysis was applied to the relationships between the fine gird extract and 6 remaining technological traits.

Table 2 presents the correlation coefficients between fine grid extract and 6 selected traits. Only in the first preliminary series, highly significant positive favourable correlation coefficient between malt fragility and fine grid extract as well as between wort viscosity and fine grid extract were observed (Table 2).

Correlation coefficients were characterised by nearing activity directions in both series (Table 2). A similar phenomenon was noted in some earlier research by Bichoński [1] and Śmiałowski [21], who examined the relationships between brewing quality with the strains of brewery barley collected in two collections and 2 series of first and second preliminary trials in 1996-1998. With other grain species, such as wheat, winter crop rye and oat the breeding material is frequently characterised by adverse correlations between quality and agronomic traits at various breeding stages [9, 17, 20, 21]. At that time, the search for the forms which could change adverse correlations becomes a necessity.

Breeding brewery barley requires from a breeder, the observance of strict technological norms. Some strong relations are observed between technological traits, therefore disruption of one trait means a change in the value of another. In order to clarity the relationships between the examined traits, an attempt was made to explain their cause-and-effect relations. The results of the path analysis of brewer spring barley strains in both series of experiments are presented in tables 3 and 4. The path analysis made in a series of first preliminary trials (synthesis from 1999-2001) indicated strongly significant direct effects between technological traits and fine grid extract. They turned out to be generally higher than the values of the correlation co-efficients (Table 3). Especially high, negative favourable direct effect (-1.185), stronger than correlation coefficient (-0.50) was observed between fine grid extract and wort vi scosity (Table 3). In this case, a negative, favourable direct effect is weakened by adverse positive indirect effects of such traits as: grain filling (0.239), protein content (0.105), malt fragility (0.152) and wort viscosity (0.190) (Table 3). The sum of indirect effects obscures the correlation co-efficient, which is significantly lower (-0.50) than the effect of direct activity effect (-1.185) (Table 3). Another important relation between fine grid extract and protein content is characterised by w strong direct effect of correlation (-0.533), thus being significantly higher than correlation coefficient (-0.49) (Table 3). It turned out that the direct effect is intensified by indirect effect of malt fragility (-0.263).

Another relationship between fine grid extract and malt fragility for which positive direct effect was observed, is also worth noting (0.461) (Table 3). The value of the effect is lower than of its corresponding coefficient of genetic correlation (0.55) (Table 3). It turned out that the reason is weakening activity of another trait, i.e. wort viscosity (-0.391), which slightly lowers the correlation coefficient between fine gird extract and malt fragility (Table 3). The analysis performed (regression - R²) indicated in 56.4 % variability of fine grid extract in a series of first preliminary trials (Table 3).

In the second preliminary trials, both genetic coefficients of examined technological traits and direct effects were of lower value than in the first preliminary trials (Table 4). An exception is the correlation coefficient between protein malt and fine grid extract (-0.66) (Table 4). In this case direct effect between these two traits (-0.426) was slightly intensified by indirect effects of the remaining trials examined (Table 4). The reason for low values of remaining correlation coefficients must be seen in a larger equalisation of brewery barley in second preliminary trials. The observed phenomenon results from the role played by second preliminary trials in pre-register attestation, in which the best, equalisation breeding strains are evaluated both with respect to brewing quality and agro-technical traits. The analysis performed (regression - R²) explained in 100 % variability of fine grid extract in second p reliminary tests.

Summing up the results of path analysis for the straits and varieties of brewery spring barley investigated in first and second preliminary trials, it turned out that only between one relationship, i.e. the protein content in the malt and fine grid extract, genetic correlation and direct effects were nearing in both experiments. Therefore, maintaining appropriate level of protein, first in the grain, than in the malt of brewery barley influences the quality of fine grid extract, which means that it determines barley technological traits.

The phenomena described here indicate also that genetic correlations between significant technological traits of brewery spring barley i.e. fine grid extract and malt viscosity as well as fine grid extract and malt protein are obscured by other, seemingly less significant technological traits such as: grain filling, malt fragility, diastatic power and fermentability. These traits might intensify or weaken, directly or indirectly, these important correlations. That is why, this phenomenon must be taken into consideration during the selection performed in order to improve fine grid extract or protein content or malt fragility of brewery spring barley.

In the experiments carried out in 1996-1998 [2003] it was found that only malt viscosity in a significant way strongly and directly influences fine grid extract. Such a varied observation indicates that both value and direction of correlation between the examined technological traits of brewery barley may be determined by examination material and modified by the environment e.g. the years of experiments. This phenomenon must also be taken into consideration while making breeding plans for brewery barley.

CONCLUSIONS

1. Strong direct correlation between malt protein and fine grid extract was observed in brewery spring barley in both series of examinations. The remaining traits i.e.: grain filling, malt fragility, wort viscosity and fermentability in a direct and strong influenced fine grid extract only on the earlier stage of breeding.

2. As between the traits of brewing quality some strong correlations were observed, in the cultivation aiming at the improvement of fine grid extract, also the activity of favourable and adverse influence of remaining traits, such as malt fragility, wort viscosity and fermentability must be taken into consideration. At the same time, thanks to these traits, the level of fine grid extract may be modified in the breeding process, using the indirect activity of other quality traits.

3. Taking into consideration all cause-and-effect relationships between the technological traits may speed up the effectiveness of cultivation of brewery spring barley with high brewing quality.

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