Some Quality Groat Characters in Oat Wild Species
Dr. Igor Loskutov
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Abstract

This research presents the results of studying (1989-1997) 16 wild species with different ploidy level. The range of variability by quality parameters have been demonstrated and valuable forms have been identified by such characters as weight of 1000 grains, percent of huskness, groat protein and oil content, groat aminoacid and fatty acid composition. Relationship between geographical origin of the accessions studied and their quality characters was found.

Introduction

The data on yields and other characters indicated that the wild and weedy relatives possess genes that can increase the productive potential of the crops (3). Cultivated and wild oat, in addition to its agricultural traits, manifests high levels of grain and green matter quality (9, 11, 18). Protein content in oat grain averages 9-12%, though maximum content in some commercial characters may reach 20% and oil percentage in groats may be as high as 11% (14, 15) with well-balanced aminoacid and fatty acid composition (10, 13). However, in a number of cases grain yield shows adverse correlation with grain protein content. Interspecific hybridisation was more efficient in the breeding process targeted at this feature (1, 8). Some wild diploids and tetraploids had high groat oil content (12-13%) (17). Hexaploid weedy oat species appeared to have 27-28% (2) of protein in naked seed, being however reported sometimes to reach 35%. According to numerous reference sources, quite many forms of hexaploid species Avena sterilis and A.fatua have been analysed for this trait, and the samples identified by such analysis are presently used in oat breeding to obtain high-yielding lines and varieties with higher protein content in grain (12, 16). The forms of A.sterilis with high protein and oil content were reported to have cytoplasmic genes which are capable to provide a 20-30% increase in the yield of a hybrid population (2). The effect of such genes takes place without depressing the increase of grain protein content. In addition to qualitative parameters, such wild forms must possess a number of agricultural features which could provide for enhancement of other properties in cultivated oat (5, 6).

Materials and methods

Having at our disposal a rich collection of wild and weedy oat species, we started studying biochemical characters of oat grain, continuing, at the same time, the analysis of commercial traits (5, 7). This study involved about 180 forms of oat species with different ploidy levels: diploids (A.pilosa, A.clauda, A.ventricosa, A.longiglumis, A.canariensis, A.hirtula, A.wiestii, A.atlantica), tetraploids (A.barbata, A.vaviloviana, A.magna, A.murphyi) and hexaploids (A.fatua, A.occidentalis, A.ludoviciana, A.sterilis).
Sowing was performed at Pavlovsk Experiment Station of VIR in 1989-1997. Borrus, a released cultivar oat from Germany, was taken as the standard reference. Evaluation of original materials was based on the methods and descriptors of VIR (4). Protein content and aminoacid composition were analysed at the Laboratory of Protein and Nucleic Acids of VIR.
The purpose of this research was to identify interspecific differences in groat protein and groat oil content and aminoacid and fatty acid composition, disclose intraspecific variation of these parameters in correlation with the geographic origin of these forms, and to trace the dependence between grain quality parameters and cultivation conditions characteristic of these species.

Results and discussion
Species Weight of 1000 grains,
g		 Percent of huskness,
%		 Groat-protein content,
%		 Groat-oil content,
%
A.ventricosa Bal. 3.9 68.9 15.4 8.7
A.clauda Dur. 4.7 55.0 10.2 8.9
A.pilosa M.B. 3.2 74.5 9.7 10.4
A.longiglumis Dur. 13.6 57.8 22.1 7.8
A.canariensis Baum 7.5 71.4 14.7 11.2
A.wiestii Steud. 5.1 59.3 19.9 8.8
A.hirtula Lag. 8.4 42.8 13.7 7.4
A.atlantica Baum 4.3 53.6 20.1 7.6
A.barbata Pott. 6.4 51.6 21.1 7.1
A.vaviloviana Mord. 8.3 41.9 17.8 6.8
A.magna Mur.et Terr. 19.6 65.5 21.9 7.6
A.murphyi Ladiz. 18.2 64.8 19.1 8.9
A.fatua L. 13.9 36.7 18.5 9.1
A.occidentalis Dur. 11.5 53.8 19.8 7.8
A.ludoviciana Dur. 15.6 44.9 18.7 9.6
A.sterilis L. 14.4 53.6 21.8 8.0

In this study, it was measured not only biochemical parameters, but weight of 1000 grains and percent of huskness. The results showed that among diploid species grain weight and percent of huskness was ranges 3.2 – 13.6 g and 42.8% - 74.5% respectively (Table). The highest groats protein content in A.longiglumis, A.atlantica, A.wiestii ranged from 19.9% - 22.1% and oil content more than 10% had forms of A.canariensis and A.pilosa. Groat oil fatty acid composition demonstrated that concentration of saturated (palmitic and stearic) fatty acids were higher in A.hirtula and A.longiglumis; monounsatured (oleic) – in A.hirtula, A.longiglumis and A.wiestii; polyunsatured – (linoleic) in A.clauda and A.pilosa, (linolenic) in A.atlantica and A.longiglumis.
The weight of 1000 grains in tetraploid species A.barbata was not high (6.4 g), but the degree of huskness was 51.6%. The average percentage of grain protein was 21.1%. The highest average values of this parameter for the study was demonstrated by the samples from Azerbaijan Iran and Portugal. Lysine content in the protein of this species averaged 5.6%, being less than in cultivated oat, but reliably higher than in hexaploid species. All accessions of A.magna had groat protein content more than 20.0%. Aminoacid composition in the present species was advantageously and reliably different from that in cultivated oat and other hexaploid species. In the forms of A. barbata the content of essential aminoacids (valine, methionine, isoleucine, tyrosine and phenylalanine) in the protein was reliably higher than in the reference cv. Borrus, lysine and threonine content was similar to cultivated oat, while leucine content was lower. These data indicate an increased nutritive value of the protein contained in this tetraploid species. The highest average values in tetraplids of groats oil content (more 8%) was demonstrated by the accessions from Azerbaijan, Spain (Canary Is.), Italy and Morocco (A.magna). Concentration of oil fatty acid showed that saturated (palmitic) fatty acid was higher in A.barbata and A.vaviloviana; monounsatured (oleic) – in A.barbata, A.vaviloviana and A.magna; polyunsatured – (linoleic) in A.vaviloviana, (linolenic) in A.barbata and A.murphyi. Correlation analysis showed that such qualitative parameters as the weight of 1000 grains and protein and oil content in grain were directly proportional to each other, whereas grain size had inverse correlation with grain huskness.
Grain weight of hexaploid species A.ludoviciana was 15.6 g. Percentage of huskness was 44.9%. The highest mean values of grain protein content (21.2-22.6%) were reported in the samples from Azerbaijan, Iraq and Israel. Lysine content in the protein of this species appeared to be the lowest among all analysed species (0.65 g per 100 g) and was closely connected with grain protein content. At the same time, the content of a number of essential aminoacids (phenylalanine) was reliably higher than in Borrus, the content of threonine, valine, isoleucine, leucine and tyrosine was at cultivated oats level, while lysine and methionine content was lower; thus this species had practically the same nutritive value as cultivated oat. The highest mean values of groat oil content (more than 8%) were reported in the accessions from Azerbaijan, Georgia and Armenia. Grain weight in this species was inversely proportional to huskness and had a reliably direct correlation with the percentage of protein in grain, the latter being in its turn inversely linked with huskness.
Another hexaploid species A.sterilis, which is regarded in numerous publications as a donor of increased groat protein and oil content, in our research also manifested higher parameters of this trait than the other species of this group. Forms from Morocco, Turkey and Tunisia were identified for the grain weight which sometimes reached the level of cultivated oat (24.3-32.7 g). The level of huskness in these accessions was the highest among this group of species and amounted at the average to 53.6%. As for the percentage of grain protein, this species had the best parameters among hexaploid species. The highest mean values (more than 21%) for all years were manifested by the forms from Israel, Morocco, Lebanon, Algeria and Tunisia. It was identified a large group of forms accumulating an increased groat protein content which was stable during the years of study and amounted to 21.3-24.4%. These accessions were: VIR-142 (Morocco), VIR-473 (Lebanon), VIR-653 (Algeria), VIR-644 (Tunisia), VIR-502, VIR-529, VIR-550 and VIR-551 (Israel). Aminoacid content of protein in A.sterilis was in many aspects similar to the parameters of the previous species with nutritive value reaching the level of cultivated oat. Isoleucine and phenylalanine content reliably exceeded the reference; threonine, valine, leucine and tyrosine equalled the reference, while lysine and methionine content was lower. The highest mean values of groat oil content (more than 8%) for all years were manifested by the forms from Iraq, Israel and Algeria. It was demonstrated a large group of accessions accumulating an increased groat oil content: VIR-431 (Iraq), VIR-502 (Israel), VIR-653, VIR-1699, VIR-1887 (Algeria). Correlation analysis showed that the weight of 1000 grains was directly and reliably linked with huskness and adversely with grain protein content. The latter, in its turn, was adversely proportional to huskness of the samples.
The most early hexaploid species A. fatua was similar in many parameters to cultivated oat. The grain weight in this species ranged 13.9 g, and grain huskness was about 30% (at the cultivated level). Grain protein percentage in A.fatua was the lowest (18-19%) among all the species studied, but exceeded the level of cultivated oat. As for the composition of essential aminoacids, this species demonstrated the level higher than in cultivated oat in the content of leucine and phenylalanine; isoleucine and tyrosine equalled with the reference; whereas lysine, threonine, valine and methionine were below the reference level, which is an evidence of insufficient nutritive value of protein in this species. Groat oil percentage in A.fatua was the highest from Greece, Ukraine, Georgia, Kazakhstan and Tadjikistan. The results of correlation analysis witnessed that huskness was directly linked with grain protein content and adversely with the grain weight.
Fatty acid composition of oil in groat in hexaploids was demonstrated that in saturated (palmitic and stearic) fatty acid was higher in A.fatua, A.ludoviciana and A.sterilis; monounsatured (oleic) – in A.fatua and A.ludoviciana; polyunsatured – (linoleic) in A.ludoviciana.

Conclusion

Thus, on the basis of the studying wild and weedy oat forms, it was determined that diploid and tetraploid species, due to less ploidy, don’t directly mating with hexaploid cultivated oat. On the other hand, a series of accessions were marked for higher protein and oil content in grain (A.magna ect.), and their aminoacid and fatty acid composition was balanced in essential aminoacids better than in other hexaploid species and better ratio of fatty acid of this species increased nutritive value. It is also worth mentioning that with a thrice lower weight of 1000 grains than in hexaploid species, the samples of this group, especially those from Azerbaijan, Portugal, Spain (Canary is.) and Morocco had the highest values of protein and oil content in grain. Direct correlation between grain size and grain protein and oil content witnessed to a possibility of using forms of this species in oat breeding practice. At the same time, many biochemical parameters of grain quality in this species were more strongly affected by changes in environments. And finally, the problems arising when inter-specific mating these species with cultivated oat would restrict the possibility to recommend it directly as a donor of high groat protein and oil content.
Hexaploid species A.ludoviciana and A.sterilis were similar to each other in many features with only one difference: the latter exceeded the former in the parameters of agricultural traits and in grain quality, especially the forms from Israel, Algeria and Tunisia. However, the parameters of grain size and percentage of huskness produced different effect upon grain protein and oil content in these species. In A.ludoviciana, forms with larger grain size had higher protein content in grain and less percentage of huskness. A.sterilis showed the opposite tendency in these parameters. At the same time, good combining ability with cultivated oat, high groat protein and oil content and nutritive value of protein and oil make it possible to recommend these species as donors in the breeding process for quality.
A.fatua did not possess a wide range of valuable agricultural traits compared with the previous species. In the percentage of protein and oil in grain they were at an intermediate level, especially the samples from Kazakhstan, Georgia and Ukraine, and exceeded the value demonstrated by cultivated oat, but they showed less nutritive value of protein. This species had the lowest percentage of grain huskness and thus it may be recommended as a donor for enhancement of quality in cultivated oat.
In the result of this evaluation it was disclosed intraspecific diversity of all parameters in correlation with the geographic origin of these species and forms. The accessions with high groat protein content mostly were origin from Israel, Morocco and Azerbaijan and the highest groat oil content forms usually were from Azerbaijan, Morocco, Ukraine and Georgia.
These studies confirmed that species A.sterilis and A.ludoviciana are the most promising and important both in terms of grain quality and in terms of transferring this trait onto cultivated oat. The research resulted in finding intraspecific variation in biochemical parameters under study, which opens a possibility to search for forms with a complex of commercially valuable properties and high grain quality.

References

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