Mass spectrometric fingerprints of seed protein for defining Lupinus spp. relationships

The Lupinus genus consists of 200-600 species with diversified morphological and biochemical characteristics that provide scope for increasing the value of protein attributes in commercial lupin species through genetic improvement. This study characterised protein polymorphism among 33 selected lupin genotypes representing 19 species from Old World and New World using Matrix-Assisted Laser Desorption Ionization Time-Of-Flight (MALDI-TOF) mass spectrometry with the aim of developing a high throughput screen for assessing variation among samples within a genetic resource. MALDI-TOF mass spectrometry analysis recognized 630 polymorphic protein mass peaks. A total of 19 protein mass peaks were identified as species specific and 23 were recognized to be generally common (observed in more than 10 species). A set of 111 rare protein mass peaks common to 2-3 species were identified to uniquely distinguish the respective species in combination with the species specific mass peaks. Overall, the seed protein profiles showed extensive diversity among the species analysed. Phylogenic analysis based on the protein mass peaks clustered the Old World smooth and rough-seeded and New World lupin species separately, in broad agreement with clustering based on morphological characters, life history, cytogenetics, DNA polymorphism and electrophoreses of seed proteins. Two New World lupin species, L. mutabilis Lindl. and L. succulentus Douglas ex K. Koch were grouped into the smooth-seeded Old World group.