An Economically Important Crop
A. sativa is an economically important crop and ranks sixth in world cereal production after wheat, rice, maize barley and sorghum (FAO, 2012). It is an important role as food for human and feed for animals in central high lands of Ethiopia; it is one of the best dual-purpose cereal crops. Ethiopia as a region with wide altitudinal range, substantial temperature, and rainfall differences with diverse edaphic conditions create a wide range of agro-ecological conditions and microenvironments.
Ethiopia, is considered as a secondary center of diversity for the oat, little has so far been done towards determining the genetic diversity, population structure and acid soil tolerance capacity screening of Ethiopian oat accessions. More nutritious and high yielding oat varieties are needed to run an efficient livestock industry as well as to secure human food security on which dependence of increasing population is taking ride.
So, it becomes important to take advantage of the germplasm available to develop the superior cultivars for specific needs.Thus, the present study was undertaken to identify or catalogue oats genotypes along with the assessment of genetic diversity prevalent in different geographical regions in the country and from USA, Netherlands and Australia.
The 176 oat accessions were used for the present investigation and they were sown in a RCBD design with two replications at each site. Observations were recorded on various morpho-agronomic characters viz; plant height (cm), internode length (cm), number of nodes per main stem of a plant, number of tillers /plant, Flag leaf length (cm), length of panicle (cm), number of spikelets per panicle, days to 50% flowering, days to maturity, biological yield per m2 (g), grain yield per m2 (g), and harvest index (%).
This study also provides one of the first reported investigations of association analysis in a diverse population of oat, and thus, it will provide a useful benchmark for comparison with future results and with results from other species. Accurate assessment of the levels and patterns of genetic diversity has tremendous importance in the analysis of genetic variability in cultivars; identifying diverse parental combinations to create segregating progenies with maximum genetic variability for further selection; and introgression of genes from more exotic germplasm to broaden the genetic diversity of oats.
The results obtained in our study provide a better understanding of genetic diversity along with its aluminium tolerance from different regions of Ethiopia as well as USA and Netherlands and Australia oat germplasm accessionsBased on molecular and agro morphological data there are no clear differentiation between populations; the population that were analyzed as genus level, A. sativa population and A. abyssinica population.
The present study revealed that the oat accessions had significant wide range variability with respect to qualitative and quantitative traits. Moreover, the variations observed (both qualitatively and quantitatively) were fairly distributed across the regions/populations the accessions were collected from. These indicated potential genetic diversity prevalent in oat accessions, which can be harnessed future breeding and conservation endeavors in Ethiopia.
A high genetic diversity exists in Ethiopian accessions as well as in USA and Netherlands- Australia accessions. There is a significantly higher variation within the populations than among the populations. In addition, there is a significantly higher variation within cultivated as well as within wild than among the cultivated and among wild. Furthermore, there is a significantly higher variation within species than among the species.The molecular diversity analysis was carried out using 19 SSR markers in all the 176 germplasm.
The SSR markers showed clear differentiation between wild and cultivated, but they failed to differentiate from Ethiopian and USA and Netherlands-Australia cultivated oat accessions. The following molecular data were recorded for allelic parameters like, number of alleles/effective alleles; average heterozygosity; genetic diversity; and Polymorphic Information Content (PIC), demonstrating the availability of adequate genetic diversity in the wild oat accessions that can be exploited in the future.
These variations in the allelic parameters were also noticeable across regions/populations sites. Peculiarly, the geographic populations, Shewa and Gondar and Arsi, had the most excessive number of effective alleles in 176 oat accessions the whole, 81 A. sativa accessions, and A. abyssinica accessions; and expected/unbiased expected heterozygosity measures.
This indicated that these regions possess higher importance towards through introgression desirable genes into other oat genotypes in Ethiopia.
The following molecular data were recorded for allelic parameters like, number of alleles/effective alleles; average heterozygosity; genetic diversity; and Polymorphic Information Content (PIC), demonstrating the availability of adequate genetic diversity in the wild oat accessions that can be exploited in the future.
These variations in the allelic parameters were also noticeable across regions/populations sites. Peculiarly, the geographic populations, Shewa and Gondar and Arsi, had the most excessive number of effective alleles in 176 oat accessions the whole, 81 A. sativa accessions, and A. abyssinica accessions.
This indicated that these regions possess higher importance towards through introgression desirable genes into other oat genotypes in Ethiopia.Cluster analysis grouped 176 genotypes into five clusters whereby the individuals within any one cluster are more closely related than are individuals in different clusters.
Our expectations were, the hexaploid specie might be grouped together and tetraploid species may have clustered together, while hexaploid and tetraploid species should have to be clustered separately since they possessed different genome. unlikely to our expectation the result showed that hexaploid and tetraploid were grouped together.
Clustering these groups were similar both in molecular and agro-morphological data. Similar results were found for molecular data. The DARwin 5.0 software was used to generate the dendrogram. All the genotypes were clustered into 3 clusters of different sizes. On the other hand, results of PCA and various recorded values of important agro-morphological descriptors were jointly used to determine the groups identified in the molecular analysis at a STRUCTURE present k=2.
As a result, the first group, USA and the Netherlands – Australia belonged to the cultivated oats, A. sativa; whilst the second groups were predominated by accessions from the Ethiopia, both cultivated and wild. Consequently, it was concluded that Cultivated oat groups had higher genetic diversity than their respective Wild oat counterparts in Ethiopian oat germplasm.
The current study showed that Root Length (RL) was affected more by Al toxicity. Lower Al toxicity levels less than 50 µM had no significant effect on the growth performance in most oat accessions, while the growth of RL showed a decline with increasing Al concentration and toxicity levels. The impact of Al toxicity on oats germplasm became influential upon toxicity level increments.
The optimum Al3+ concentration for tolerance level could be 112.5 µM oats. Thus, these accessions should not be recommended in area where soil acidity is predominant. However, A. vaviloviana accessions were highly Al tolerant as revealed by root growth performance and can be promoted in area where soil acidity is a challenge. This study is the first of its kind to evaluate the performance of Ethiopian oats to Al-toxicity.
The study clearly showed the possibility of developing lines and genotypes that can tolerate acidity in Ethiopian context and support agricultural development in acidic soil area in the country. In conclusion, the present study generated unique outcomes in terms of directing the phenotypic and molecular genetic diversity; population structure of the genepools; and to identity of sub-groups up to the species level. It is considered to put the platform for future breeding and genetic resource conservation programs in Ethiopia.
