Understanding the genetic determinants and population structure of Pongamia pinnata (L.) Pierre for oil yield and its properties using transcriptome derived SSR markers

Pongamia is a commercially important tree; its seed oil has the potential to be used as a biofuel worldwide. The seed traits have huge genetic diversity, which suggests its scope for genetic improvement. However, lack of improved genetic stock is a major bottleneck to establishing plantations for biodiesel production. Assessment of genetic diversity, population genetic structure, and biodiesel properties in 18 Pongamia accessions were studied using eight morphological traits and 11 SSR markers. The accessions exhibited a high degree of genetic variability at both levels, indicating the potential scope of this population for further tree breeding. Certain morphological traits are governed by additive genes and may provide indirect selection to yield improvement. Based on the dissimilarity of the coefficient, NRCP10 and NRCP20 were identified as the most distinct accessions, and, interestingly, these two accessions also have a higher cetane index for better biofuel properties. The dendrogram divided 18 accessions into two major clusters. The principal component analysis revealed a total of 70.92% variability in this population. On the other hand, molecular characterization using eleven SSR markers exhibited a significant level of polymorphism across the accessions. A dendrogram based on SSR markers clearly separated the 18 accessions into five groups, which resulted in NRCP11, NRCP14 and NRCP21 being the most distinct accessions. Also, the dendrogram conforms to the first and second coordinates by principal component analysis. The population structure of these 18 accessions also revealed the presence of two gene pools. In addition, analysis of molecular variance found 97% of the variability within the population, while only 3% occurred between populations. The genotypes identified in this study using morphological and molecular markers could be selected as donor parents in Pongamia tree breeding programs to improve economic trait values.