Genetic Diversity, Relation Between Characters, and Aluminium Toxicity Tolerance of Avena Species From Ethiopia
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Date
2018-11-12
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Addis Ababa University
Abstract
Oat is used for animal feed and human food. It is well adapted to a wide range of environments, but it
grows well in cool-temperate and tropical African regions, particularly Ethiopia. Ethiopia is one center of
origin for A. abyssinica and A. vaviloviana oat species, but in Ethiopia oat is a minor crop and only a few
cultivars have been used. Despite the many benefits oat has, the production and productivity of the crop
have been highly constrained by the inadequacy of improved varieties and narrow genetic base of the
germplasm used in breeding. Aluminium toxicity is a substantial agronomic problem in Ethiopia and
developing Al tolerant oat cultivar is crucial. Therefore, this study was primarily aimed to assess the
genetic diversity, population structure, relation between characters and evaluating the aluminum toxicity
tolerance potential of oat accessions in Ethiopia. A total of 176 accessions from five Avena species
namely, A. sativa (82), A. fatua (18), A. sterilis (12), A. abyssinica (44), and A. vaviloviana (20) were used
for morpho-agronomic experiment and molecular genetic diversity study. Except for the number of
accessions of A. sativa obtained from USA, the Netherlands, and Australia all the accessions were from
Ethiopia. The mopho-agronomic experiment was conducted using RCBD design at Debre Brehan and
Holetta Agricultural Research Centers. Data were collected on 22 qualitative and 12 quantitative traits.
The Shannon diversity index was analyzed for qualitative traits. The mean, ANOVA, heritability, genetic
advance, principal component analysis, clustering, cluster distance, and association of traits were analyzed
for the quantitative trait. The molecular genetic diversity analysis was carried out at ILRI-BecA Hub,
Nairobi, Kenya, using 19 SSR markers with fluorescently labeled forward primers. The analysis of the
allelic pattern and distribution, MANOVA, clustering, PCoA, population structure, and differentiation
were analyzed. The hydroponic experiment was conducted at Addis Ababa University to evaluate
aluminum toxicity tolerance of the accessions. The hydroponic experiment was carried out on 150
accessions including accessions from, A. sativa (74), A. fatua (16), A. sterilis (5), A. abyssinica (40), and
A. vaviloviana (15). Regarding morpho-agronomic traits, accession had low to high heritability and
genotypic advance of mean. The wide range of heritability and genotypic advance of mean were found in
five Avena species. Similarly, wide range correlation of grain yield with other traits were observed. The
Agglomerate hieratical clustering at a phenotypic level among five Avena species revealed three clusters.
The first two clusters were predominantly consisted of A. sativa accessions with only a few wild Avena
accessions and the third one cluster with two sub-clusters consisted accessions of wild species. Most
accessions of A. abyssinica and A. fatua were clustered together in one group (sub-cluster 1) regardless to
their geographical origin, and similarly A. sterilis and A. vaviloviana accessions were found together in
another group (sub-cluster 2). The distances between clusters of species were different and relatively the
highest cluster distance was observed between A. sativa and A. abyssinica accessions. Results of analysis
of molecular variance (AMOVA) showed that 26% variation was between the wild and the cultivated
species. Calculated FST value between wild and cultivated species was high (FST = 0.080), with moderate
gene flow (Nm = 0.943). In addition, 33% of genetic variation was due to the differences among oat
species. The calculated FST value among oat species was high (FST = 0.325) with a moderate gene flow
(Nm = 0.519). We found FST value of A. sativa populations and A. abyssinica populations to be 0.051 and
0.034, respectively. Unweighted pairwise method with arithmetic mean (UPGMA) clustering and
Principal Coordinate analyses (PCoA) revealed that accessions from different collection sites clustered
together. Three groups of clusters were recognized in the UPGMA Dendrogram, the first cluster contained
A. abyssinica and A. fatua, the second cluster contained A. vaviloviana and A. sterilis, and the third cluster
contained only A. sativa accessions. Not only the UPGMA clustering but also had the PCoA clustered
revealed the wild and cultivated species grouped separately. At K=2 (optimal gene pool number), two
gene pools were found; one dominated by the cultivated oat and the second by wild oat species.
Predominantly, A. sativa had one gene pool type, whereas, A. sterilis and A. vaviloviana had an admixture
of the two gene pools. A. abyssinica and A. fatua accessions had the second gene pool type (wild gene
pool). The oat species was variable in Al3+ toxicity tolerance to acid soil and the majority of the accessions
were tolerant to aluminium toxicity. On the basis of the species type, ploidy level, and genome type, that
a comparison was made and it was found more similarity between species of different ploidy levels and
genome type, for example, A. sterilis and A. vaviloviana and between A. abyssinica and A. fatua than
species having similar genome and ploidy level. A. sativa had relatively high genetic distance to the four
wild Avena species, especially A. abyssinica and A. fatua. Low differentiation among populations may
imply significant gene flow through the exchange of planting materials among farmers. The high genetic
diversity from morpho-agronomic traits within a population would be harnessed for oat improvement.
That the majority of the accessions are aluminium toxicity tolerance shows the potential of the oat to
produce cultivars tolerant to acidic soil. The best top 5% performing accessions for grain yield and other
important agronomic traits and the best top 5% aluminium toxicity tolerant accessions were identified. It
is recommended that the breeder would be consider these for the future improvement of oat crop. It is
recommended that future research would be for production stability of identified accessions across a wide
range of environment and their Al toxicity potential in the actual field condition. Thus, it is considered
this study will provide useful information for the breeders and conservationists for proper conservation
management, and utilization of oat germplasm and improve oat production and productivity to sustain
food security.
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Keywords
Morpho-Agronomic, Avena Species, Oat, Ssr Marker, Aluminium Toxicity Tolerance, and Genetic Diversity