ANNOUNCEMENTS
The present study was conducted with the following aims and objectives:
1. Assessment of genetic diversity using TE-AFLP markers: A total of 275 accessions were used for genetic diversity analysis. The current study led to evaluation and identification of suitable AFLP technique for analysis of genetic diversity in P. pinnata germplasm. In this regard, a relatively less known but highly robust method of TE-AFLP was shown to be useful. The ease in scoring TE-AFLP profiles is extremely important and especially desirable in studies requiring genotyping of large number of individuals distributed across many gels.The study showed that the genetic diversity in Pongamia is high even within smaller geographic distances. This shows that there is high scope for selection of trees with desirable traits in the existing plantations. The study also identified a core germplasm of 20 accessions with high genetic diversity. As a long term strategy, the diverse accessions can be used to generate new and improved genotypes through controlled crossing and field selection. Some of the accessions with high seed size and oil content can be used for new plantations by utilizing clonal techniques such as macro and micropropagation.
2. Development of microsatellite markers: This is the first report on isolation and characterization of microsatellite markers in Pongamia till date. In the present study, 39 microsatellite loci were isolated and sequences submitted to GenBank. Nine of these microsatellites produced polymorphic bands on a panel of eight accessions. The nine polymorphic microsatellite markers were also characterized across a panel of 24 Pongamia accessions. Despite the modest number of accessions analyzed, the results indicate that the new microsatellite markers developed in this study will serve as a very useful tool for genetic diversity analysis, mapping and clonal identification in P. pinnata.
3. Oil content and fatty acid analysis: For fatty acid analysis using gas chromatography (GC), 38 candidate plus trees (CPTs) were selected based on oil content from both the tails (the top as well as the bottom) of distribution in 157 accessions. In case of developing seeds, all the sampled seed stages were analyzed. Selection of Pongamia accessions with high oil content and higher proportion of unsaturated FAMEs would be desirable. Seeds harvested at full maturity (255 days after anthesis and onwards) are expected to contain maximum oil content with high oleic acid content and cetane value which are desirable for biodiesel production.
4. Estimation of outcrossing rates: The estimates of outcrossing rates based on AFLP and SSR alleles showed that outcrossing is the predominant mode of reproduction on Pongamia. This is the first study on Pongamia using dominant AFLP and codominant SSR markers for study of mating-system.
5. Population structure and marker-trait association: Population structure indicated presence of nine clusters in the dataset based on allele frequencies. This again indicates towards a high genetic diversity and possibility of selection in relatively smaller geographical areas. Marker-trait association between TE-AFLP markers and oil content indicated two markers, found to be associated with oil content within limits of very high statistical significance and several others within 95% confidence level. These markers need to be validated on another independent population for applications in marker assisted breeding.
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