Abstract
The inter relationships between the two progenitors is interesting as both wild relatives are known to be the great untapped gene reservoirs. The debate continues on granting a separate species status to Oryza nivara. The present study was conducted on populations of Oryza rufipogon and Oryza nivara from Eastern India employing morphological and molecular characteristics. The cluster analysis of the data on morphological traits could clearly classify the two wild forms into two separate discrete groups without any overlaps i.e. lack of intermediate forms, suggesting the non-sympatric existence of the wild forms. Amplification of hyper variable regions of the genome could reveal 144 alleles suggesting high genetic diversity values (average He = 0.566). Moreover, with 42.37% of uncommon alleles between the two wild relatives, the molecular variance analysis (AMOVA) could detect only 21% of total variation (p < 0.001) among them and rest 59% was within them. The population structure analysis clearly classified these two wild populations into two distinct sub-populations (K = 2) without any overlaps i.e. lack of intermediate forms, suggesting the non-sympatric existence of the wild forms. Clear differentiation into two distinct groups indicates that O. rufipogon and O. nivara could be treated as two different species.
Highlights
Rice, the world’s most important food crop and primary food source for more than one third of the world’s population, accounts for around half of the calories consumed by three billion Asians
The data derived from isozymes[12], RAPIDs13, allozymes and RFLPs14, transposon display markers[15], tourist sequences[16], miniature inverted-repeat transposable elements inAFLPs17, SSRs13, STSs18 and various gene sequences[19,20,21] did not detect any significant divergence between O. nivara and O. rufipogon, while the data derived from AFLPs22, microsatellites[23,24], combined sequence data from chloroplast, mitochondrial and nuclear DNA25 and SNPs26 did indicate differences to grant a species status to O. nivara
The present study reports the results based on detailed investigations on morphological characteristics and several loci at molecular level in O. nivara and O. rufipogon populations with an objective to understand their inter relationship and evolutionary aspects
Summary
The world’s most important food crop and primary food source for more than one third of the world’s population, accounts for around half of the calories consumed by three billion Asians. The crop improvement programs are dependent on continuous infusions of genes/QTLs from landraces and wild relatives to address the genetic enhancement programs and this path requires an assessment of diversity in the base populations to select desirable genotypes for use. Though utilization of natural variation available in the landraces is a continuous ongoing process of the crop improvement programs, it is important to explore the wild germplasm forms with novel traits as wild relatives of cultivated crop species are increasingly recognized as a valuable repository of useful variation. Oryza rufipogon and Oryza nivara, the two closest relatives of Asian cultivated rice (O. sativa L.) are considered to be its progenitors[2,3]. As the wild relatives of rice can be an important source of beneficial genes in rice breeding, O. rufipogon and O. nivara have long been the subject of extensive taxonomic, phylogenetic and population studies[3,4]. The data derived from isozymes[12], RAPIDs13, allozymes and RFLPs14, transposon display markers[15], tourist sequences[16], miniature inverted-repeat transposable elements inAFLPs17, SSRs13, STSs18 and various gene sequences[19,20,21] did not detect any significant divergence between O. nivara and O. rufipogon, while the data derived from AFLPs22, microsatellites[23,24], combined sequence data from chloroplast, mitochondrial and nuclear DNA25 and SNPs26 did indicate differences to grant a species status to O. nivara
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