Genetic diversity, seed traits and salinity tolerance of Millettia pinnata (L.) Panigrahi, a biodiesel tree

The leguminous tree, Millettia pinnata (pongamia) produces oilseed suitable for biodiesel production. Assessment of oil production and genetic, morphological and physiological traits are required. Collections from the Forest Products Commission in Kununurra, Western Australia were compared with accessions from India, Indonesia, Queensland and the Northern Territory in Australia. Molecular diversity, examined using the internal transcribed spacer region, indicated distinctiveness of genotypes from Java, Indonesia. Seed traits varied across trees with the smallest seeds from Indonesia and the largest from Kununurra. Oil content varied across trees with a minimum of 28 % in an Indonesian accession and the highest of 45 % from Kununurra. Major fatty acids across trees were oleic (51 %), linoleic (19 %), palmitic (11 %) stearic (6 %), linolenic (4.5 %) and behenic (4.5 %) acids. Seed weight and oil content per seed of developing seeds increased with a sigmoid pattern and oleic acid was the major fatty acid throughout seed development. Waterlogging and salinity tolerance were assessed. Four month-old seedlings from Kununurra, Western Australia and India were exposed to: non-saline drained control, saline drained, non-saline waterlogged and saline waterlogged treatments. Seedlings were waterlogging tolerant. Salt, applied in weekly increments of 50 mM, led to reduced survival, height growth rate, leaf number and stomatal conductance and increased concentrations of leaf Na⁺ and Cl⁻. Salinity tolerance was 200 mM NaCl under saline drained and 150 mM NaCl under waterlogged conditions. Milletia pinnata diversity could be exploited for selection of superior genotypes for oil production on marginal land.