ST. PETERSBURG
I. G. Loskutov
N.I.Vavilov Institute of
Plant Industry,
St.Petersburg, 190000, Russia.
i.loskutov@vir.nw.ru
This research
(1988-2001, St. Petersburg, Russia) presents the field results of studying
about 2000 accessions of 22 wild oat species of different ploidy levels. The study was targeted at agronomic traits
and resistance to the most widespread diseases (assessment based on the digital
code scale): crown and stem rusts, powdery mildew, Helminthosporium leaf
blotch, Septoria blight, Mirothecium necrotic mottle and barley
yellow dwarf virus (BYDV). Besides, a representative collection of all species
was analysed for groat protein – amino acid content and groat oil – fatty acid
content. The study’s representative set of accessions of genus Avena L. species with different ploidy
levels helped determine intraspecific diversity in all researched characters. A
majority of identified sources may be directly involved in the breeding process
for disease resistance, agronomic traits, and grain quality in oats.
Key words: agronomic traits, Avena
species, disease resistance, oat protein and oil content.
Comparative
analysis of the whole specific diversity of oats was incited by the profound
interest to use these forms in breeding practice, and was reinforced by the
recent conduct of plant immunological, biochemical and other studies (Frey,
1983; Harder et al., 1992; Leggett, 1992).
The practical importance of interspecies hybridization lies in
recombining properties of various species that drifted apart in the process of
evolution. With this, the cultivated species, in most cases, have lost numerous
traits initially inherent in their wild ancestors. Resistance to unfavorable
environmental factors, a wide range of adaptation to diverse soil and climate
conditions, resistance to pathogens, and a number of other characters encompassing increased productivity and quality
– all of these present unique breeding sources for oat improvement (Frey, 1994;
Loskutov et al., 1997; Ohm et al., 1992; Webster, 1986; Welch, 1995;). The fusion of high biochemical and agronomic parameters in one
cultivar has been the goal of breeding in the past years. According to many
researchers, the utilization of intra- and inter-specific hybridization
together with various breeding techniques may raise the percentage of quality groat
components to a very high level, while the nutritive value of such grain will
remain unchanged (Frey, 1991; Welch et al., 1997).
The
vast area of distribution of wild oat species provides for the formation of
extensive intra-specific diversity of the characters in the polyploidy rank. At
the same time, further search for and utilization of new oat breeding sources
for breeding purposes is one of the objectives pursued by the Vavilov Institute
of Plant Industry (VIR) in studying its global germplasm collections (Loskutov
et al., 1999; Loskutov, 2002). The study of the representative set of
accessions of genus Avena L. with
different ploidy levels has made it possible to disclose intra-specific
diversity of all characters involved in the research, which will contribute to
a targeted search for the best breeding sources and broadening the genetic base
of the released oat cultivars.
The research conducted in 1988-2001 in the fields of
Pushkin Laboratories of VIR (St.Petersburg, Russia) encompassed over 2000
accessions belonging to 22 wild oat species. Field data were obtained on a
number of agronomic traits and resistance to the most widespread diseases
(assessment based on the digital code scale): crown and stem rusts, powdery mildew,
Helminthosporium leaf blotch, Septoria leaf blight, Mirothecium
necrotic mottle and barley yellow dwarf virus (BYDV). The
research was based on the International Descriptors of Avena L. (1984) and Oat
Descriptors List (1985). Besides, the representative collection of all species was analyzed for
groat protein content – amino acid content and groat oil content – fatty acid
content.
As
a result of this study (Table 1), when crown rust (caused by Puccinia coronata
Cda. f. sp. avenae Faser et Led.) resistance had been assessed on the
level of species, it was observed that most diploid wild species were missing
this character. Among the tetraploid
species, resistance was observed in most species. Hexaploid species A.
sterilis was the most resistant and promising for character-targeted
breeding. A. ludoviciana and A. occidentalis may also be regarded as
promising. Resistance was most
expressed in the hexaploid accessions from Spain, Italy, Turkey, Israel, and
Iran. Resistant forms for all groups of
species came mostly from North Africa, such as Tunisia, Algeria and Morocco.
While
assessing stem rust (caused by Puccinia graminis Pers. f. sp. avenae
Eriks.) resistance, variation of responses in the wild species studied was
wider than in cultivated oats. At the same time, among few diploid species
medium resistance to this disease was identified only. Tetraploid wild species
were characterized as strongly susceptible to this pathogen. All hexaploid wild
species, on the average, demonstrated medium resistance to the agent of stem
rust. Resistant forms were identified among the accessions from Italy, Iran,
Iraq, Israel, Tunisia, Algeria, Morocco and Ethiopia. Group resistance to major
obligate fungal diseases (crown and stem rust) was observed in the forms
belonging to species A. longiglumis (Al),
A. canariensis (Ac), A. hirtula (As), A. barbata (AB), A.
agadiriana (AB), A. magna (AC), A. insularis (CD), A. macrostachya (AA), A.
occidentalis and A. sterilis (ACD).
The highest
resistance to powdery mildew (caused by Erysiphe graminis D. C. f. sp. avenae
Em. March.) was shown by all Azerbaijan accessions of diploid and tetraploid
species only. In the majority of hexaploid forms this disease was not
manifested in the given environments.
Resistant to oat leaf blotch
(caused by Helmithosporium avenae Eidam.) was identified in some
forms of diploid species. Among the tetraploid wild species, high resistance
was observed in the species with AC genomes, A. magna and A. murphyi.
Hexaploids demonstrated medium resistance against this pathogen. Worth
mentioning is the strong resistance of A.
occidentalis. The disease’s severity was minimal in the accessions from
Krasnodar Region of Russia, Spain,Italy, Azerbaijan, Turkey, Iran, Iraq,
Lebanon, Israel, Morocco, Tunisia and Ethiopia.
Resistance to oat
leaf blight (caused by Septoria avenae Frank.) was observed in
the diploid species containing variants of the A genome. Among the tetraploid
wild species, resistance to this diseases was obvious in the perennial species A. macrostachya and some other species. The hexaploid diversity of wild species
harbored sufficient number of resistant forms. The most resistant forms were
the accessions from Spain, Italy, Portugal, Czechia, Turkey, Iran, Israel,
Morocco and Algeria.
Resistance to oat
necrotic mottle (caused by Mirothecium verrucaria Ditmar. ex Fr.) was
demonstrated by the accessions collected in various regions of Azerbaijan and
belonging to the diploid and tetraploid species and the forms of different
geographic origin of tetraploids too. A majority of the hexaploid forms with
resistance to this disease had originated in Russia, other CIS countries,
Turkey and Algeria.
Medium tolerance
to BYDV (caused by Hordeum virus nanescens Rademacer et Schwarz.)
was observed in the
diploid species with A genome variants. An overwhelming majority of tetraploid
species with different genomes had medium tolerance to this virus, except
highly susceptible A. agadiriana (AB)
and A. murphyi (AC). All hexaploid
species basically demonstrated medium tolerance to BYDV, with A. occidentalis having the highest
percentage of resistant accessions. The strongest and medium tolerance was
typical of the oat forms from Greece, Turkey, Syria, Israel, Morocco, Algeria
and Tunisia. Comparing the data of BYDV resistance and strong aphid
colonization ascertained identification of BYDV resistant accessions belonging
to diploid species A. clauda, A. pilosa (Cp), A. damascena (Ad), A.
canariensis (Ac) and A. hirtula (As).
The results of
our field researches reported great diversity in the structure and separate
elements of panicle (Table 2). Variation of these descriptors was insignificant
throughout the years of study. Analyzing the panicle structure on the species
level certified that such parameters as panicle length, number of spikelets and
panicle density varied greater in the diploid wild species that in other groups
of species. The smallest values of these parameters was observed in the early
species A. canariensis, with a very
short panicle of 12 cm, 9.4 spikelets per panicle, and panicle density no more
than 0.7. A. damascena also had a
small number of spikelets per panicle and low panicle density, while A. longiglumis demonstrated minimal
panicle density in spite of the fact that the panicle of this species was long
enough (24.4 cm). Maximal values of all three parameters were observed in
relatively species A. wiestii and A. hirtula. Tetraploid species
demonstrated lesser variation of these parameters. Minimal panicle length,
spikelet number and panicle density were reported in the interrelated species A. magna, A. murphyi and A. insularis.
Maximal values of the parameters studied were identified in the forms of A. barbata. Studying the diversity of
the same descriptors of panicle structure in hexaploid species proved their
variability to be minimal. The smallest values of panicle length, spikelet
number and panicle density were observed in A.
occidentalis and A. sterilis,
while the highest ones were demonstrated by the forms of A. fatua.
Besides, field
evaluation of wild oat species cast light on the rich diversity in kernel
characters (Table 3). Analyzing the percentage of husk and size of kernels on
the species level helped to determine that diploid wild species had greater
variation of these descriptors than the other groups of species. On the whole,
it was ascertained that diploid species had the highest values of husk
percentage and the lowest of kernel size. The least percentage of husk (43-46%
on the average) was observed in A.
damascena, A. wiestii and A. hirtula, and the greatest among all
species studied (60-70%) in A. ventricosa,
A.pilosa, A. longiglumis and A.
canariensis. The size of kernel was notable in the forms of A. longiglumis with 1000 grain weight
over 14 g. The smallest values of this descriptor (3.6-3.7 g) among all species
studied were shown by A. ventricosa and
A. atlantica. Variation of these
parameters was clearly less in tetraploid species. A. vaviloviana appeared among the species with the smallest (32.7%)
percentage of husk (on the level of A.
sativa), while A. magna and A. murphyi demonstrated the highest
values (58.9-59.5%) among the tetraploid species. The same two interrelated
species A. magna and A. murphyi were also distinguished for a
large size of their kernels, since their 1000 grain weight (23.5-23.8 g)
reliably exceeded maximal average values of all species studied. The smallest
size of kernel (7.2-9.2 g) was observed in the species with the AB genome, A. barbata and A. agadiriana. Hexaploid species demonstrated even less variation
in the structure of kernel than tetraploid ones. A. fatua was reported to be among the wild species with the lowest
(38.5%) percentage of husk (on the level of A.
sativa, 31.7%), while A. sterilis
had the highest values (53.2%) among this group of species. Variation of kernel
size (15.1-17.1 g) was insignificant among these species, being comparable with
A. sativa (15.9 g).
The data of
biochemical research (Table 4) on wild and weedy field oat species showed the
highest groat protein content (over 20.0%) in the accessions of diploid A. longiglumis and A. atlantica, tetraploid A.
magna and A. barbata, and
hexaploid A. sterilis. Potential
sources of high protein content would be A.
murphyi and A. occidentalis (over
19.0%). High nutritive value of protein was notable in tetraploid A. barbata (5.6% of lysine in protein).
Hexaploid species appeared to have the percentage content of lysine and other
essential amino acids in protein comparable with the level of A. sativa. Noteworthy for high groat oil
content (7-10%) were accessions of diploid A.
pilosa and A. canariensis,
tetraploid A. murphyi and A. magna, hexaploid A. fatua, A. ludoviciana and A.
sterilis. The quality of oil in oat may be determined by the content of
monounsaturated fatty acids, such as oleic acid capable of prolonging oil
preservation time during storage. The highest content of oleic acid (over 46%
of the sum of acids) was detected in the forms of diploid A. hirtula, A. longiglumis and A.
wiestii, tetraploid A. barbata, A.
vaviloviana and A. magna,
hexaploid A. fatua and A. ludoviciana. At the same time,
biological activity of such oil is determined by the correlation between
linoleic and oleic acids that should be equal to one. This correlation was
observed in the accessions of diploid A.ventricosa,
A clauda, A. pilosa and tetraploid A.
vaviloviana. This research resulted in mapping the geographic distribution
of intraspecific diversity with regard to all oat species and forms. It appeared
that accessions with high groat protein content had originated mainly from
Israel, Morocco and Azerbaijan, while those with high groat oil content from
the Ukraine, Azerbaijan, Georgia and Morocco.
The study of such
an representative set of accessions of genus Avena L. with different ploidy level made it possible to display
intraspecific diversity on all the characters involved. A part of tetraploid
species and especially hexaploid ones identified as sources of the assessed
descriptors may be directly included in the breeding process for disease
resistance, agronomic traits, and grain quality for feed and food. Numerous
researches in this direction and practical results of oat breeding have
evidenced that utilization of wild species alongside with the cultivar
diversity of cultivated forms is the most promising trend of oat breeding,
capable of broadening genetic base and reducing genetic erosion of this crop.
Frey K.J. Genes from wild relatives for improving
plants. // Crop improvement research, 1983, p.1-20.
Frey K.J. Genetic resources of oats. // In: Use of
plant introductions in cultivar development. Part 1, 1991, CSSA Special publ.
N.17, p.15-24.
Frey K.J. Remaking a crop gene pool: the case history of Avena. //
Proceedings of SABRAO seventh international congress and WSAA symposium held at
Academia Sinica. Volume I. 1994, No. 35, p.1-14.
Harder D.E., Chong J., Brown P.D., Sebesta J., Fox S.
Wild oat as a source of disease resistance: history, utilization and prospects.
// Proc. 4th Int. Oat Confer., Adelaide, Australia, v.II, 1992a, p.71-81.
International descriptor list genus Avena L. 1984,
Leningrad, USSR.
Leggett J.M. The conservation and exploration of wild
oat species. // Proc. 4th Int. Oat Confer., Adelaide, Australia, v.II, 1992,
p.57-60.
Oat Descriptors List, IBPGR, 1985, Rome, Italy.
Ohm H.W., Shaner G. Breeding oat for resistance to
diseases. // In: Oat Science and Technology. Ed. by H.G.Marshall and
M.E.Sorrels. Agronomy No.33, USA, 1992, p.657-698.
Webster F.H. (ed.) Oat. // Chemistry and technology.
Amer. Ass. Cereal Chem., USA, 1986, 433 pp.
Welch R.W. The chemical composition of oats. // In:
The oat crop. Production and utilization. Ed. by R.W.Welch. Chapman & Hall.
1995, p.279-320.
Welch R.W., Leggett J.M. Nitrogen content, oil content
and oil composition of oat cultivars (A.sativa) and wild Avena
species in relation to nitrogen fertility, yield and partitioning of
assimilates. // J. Cereal Sci., 1997, 26, p.105-120.
Лоскутов
И.Г., Мережко
В.Е. Овес.
Каталог мировой
коллекции
ВИР. вып.686, С-П., 1997, 83
с.
Лоскутов
И.Г., Чмелева
З.В., Губарева
Н.К., Хорева В.И.,
Низова Г.К.
Овес. Каталог
мировой
коллекции
ВИР., вып.704, С-П., 1999, 44
с.
Лоскутов
И.Г. Овес. Каталог
мировой
коллекции
ВИР., вып.735, С-П., 2002, 73
с.