Provenance-related seed heterogeneity and germination in Brassica insularis Moris

Morphological seed heterogeneity, defined as the production of different types of seeds by a single individual, appears in many different species of angiosperms and it is also reported for the genus Brassica. B. insularis is a member of the B. oleracea L. group which occurs only in Corsica, Sardinia, Sicily (Pantelleria) and Tunisia (La Galite) and is inserted in the Annex II of Habitats Directive 92/43/EEC. Seeds of B. insularis, collected in 2010 from three Sardinian populations [Planu Sartu and Masua (SW Sardinia) and Isola dei Cavoli (SE Sardinia)], were analyzed through an image analysis system. In addition, germination tests were conducted on seeds from each population, in the light (12/12), at a range of constant temperatures (5-25°C) and at an alternating temperature regime (25/10°C). The morphocolorimetric analysis, clearly identified seeds from different populations (in 97.6% of the cases) and discriminated three chromatic categories (black, orange and brown) for seeds belonging to the “Isola dei Cavoli” population, with a percentage of correct identification of 90%, while seeds of the two other populations were morphologically homogenous. Germination ranged from 45% to 60% for “Planu Sartu” and “Isola dei Cavoli” populations, respectively and temperature had not a significant effect. Seed moisture content (%) did not vary significantly among chromatic categories, highlighting as heterogeneity was not related to different stages of seed maturation. Germination was highly influenced both from colour and temperature, and high germination percentages (ranging from 50% to 80% for black and orange seeds, respectively) were detected at 5°C. These results showed the significant variability in morphology and germination among B. insularis seeds from different provenances, indicating the presence of morphological and physiological seed heterogeneity in this species.