Our results are consistent with the previous studies indicating high level of landrace accession polymorphism. Landraces from Ethiopia were highly polymorphic and formed a distinct and separate grouping from Australian cultivars, breeding lines, and European cultivars, which cluster together, probably revealing their pedigree and breeding history . Further development of molecular markers and application in genetic diversity studies could enhance our understanding of white lupin genetic resources and promote their use in modern breeding. The Greek landscape is characterized by a mountainous terrain, with numerous peninsulas and islands, and is considered a hotspot of L. albus diversity. Such isolated regions, justify divergence of local landraces, explaining the finding that landraces from Andros and Lemnos islands and from Mani peninsula are clustered separately from the cultivars examined. Additionally, landraces from Andros island are distinctly diversified from the rest accessions, implying that Andros constitutes a genetic pool of unique genes, potentially useful for white lupin breeding. Eventual exchange of landraces between Greek farmers and dispersal of their cultivation farther than their local point of origin may explain landrace sub-clusters on the dendrogram.
It is also a common practice for smallholder farmers to use a portion of the seed yield for the next growing season, exclusively, or in mixtures with high yielding cultivars. Long periods of recycling the seed of a commercial variety, along with potential adaptation pressure and selection by the farmers, promote the generation of new variability, resulting in new landraces that are well adapted to the specific geoclimatic conditions and to their traditional management and uses . Moreover, potential gene flow from neighboring white lupin cultivar crops could justify that landraces appear genetically in close proximity with commercial germplasm. Quinolizidine alkaloids are predominantly found in high levels in natural populations and landraces, making lupin a repulsive choice for lambs and goats, that feed on pasture . That justifies the presence of white lupin natural populations throughout uncultivated lands, that shelter underutilized genetic diversity. QA biosynthesis occurs in the vegetative upper part of the plant, and they are subsequently transported to the seeds. Modern breeding strategies focus on creating elite cultivars, with low alkaloid content , as well as cultivars that retain QAs in vegetative tissues, thus producing hardy plants with “sweet” seeds . Their biosynthesis is regulated by five different loci, with pauper being thoroughly investigated thus far, on account of its contribution to QA synthesis regulation. Regarding the accessions under examination, the “sweet” pauper marker was detected in all cultivars, in breeding lines GRKML and GRKAL, and in GR26 landrace.
Absence of the “sweet” pauper marker from the vast majority of the landraces is in accordance with their high QA content. However, presence of the marker in high QA genotypes, like the cultivar “Multitalia”, makes this marker a weak predictor of low QA content with broad applicability. In Mediterranean farming systems, white lupin is considered a winter crop and sowing takes place in autumn, in order for the crop to take advantage of the late winter rainfalls. Thus, sufficient seed filling is succeeded before the early dry spells that occur in May, which have been more frequent and severe in Mediterranean ecosystems, due to the climate change . Early flowering is considered to be an effective stress escape mechanism, in that it promotes fulfillment of the plants biological cycle, prior to terminal drought stress . Additionally, genotypes non-responsive to vernalization, suggest crops suitable for spring sown cultivation, in northern regions, with long lasting winter. While white lupin germplasm native to the Balkan peninsula has been previously characterized as vernalization responsive , among the local landraces under investigation, GR3, GR7, GR12, GR16, GR19, GR21, and GR26 hold both SEPALLATA 3 and FLOWERING LOCUS T early flowering alleles, implying a vernalization independence-promoting regional microclimate at the collection sites . Moreover, the early flowering allele of SEPALLATA 3 was detected in all commercial varieties, except for Ulysse.
The inability of FTa1 primer set to hybridize in three landraces from Andros island and in cultivars Frieda and Celina,suggest contingent mutations located at the primer binding site, in the genomes of those accessions . The GIGANTEA early flowering promoting allele was detected only in GR5, GR10, and Frieda cultivar. However, further experimentation on the aforementioned landraces is needed, in order to examine the predictive power of those molecular markers, and their potential implementation in white lupin breeding programs. Alleles that confer resistance to anthracnose, were previously found only in Ethiopian landraces, which are distinctly related to European improved germplasm. Resistanceconferring alleles, located in antr04_1/antr05_1 and antr04_2/antr05_2 loci, were also detected in the Greek landraces examined, with GR23 and GR25 from Andros, having both of them in their genome . Summarizing these results, molecular markers linked to important agronomic traits have been identified in white lupin germplasm from the Greek rural areas.