Anatomical Basis of Shatter-Resistance in the Oilseed Brassicas

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Abstract
Anatomical features of the siliqua valve and suture were studied in 13 Brassica accessions representing B. napus, B. campestris and B. juncea in order to investigate the basis of shatter-resistance and the mechanism of shattering (dehiscence). The high level of shatter-resistance of certain accessions of B. campestris var. Yellow Sarson and var. Brown Sarson was associated with the absence of an abscission (separation) layer in the region of attachment of the siliqua valve to the replum. There were no differences in this regard between intermediate shattering and shatter-susceptible accessions; both these types had a completely developed abscission layer. Orientation of the tissue and of the microfibrils of the cells of the siliqua valve did not differ between different layers of the valve in any of the accessions studied. This implied that the forces giving rise to dehiscence (shattering) are unlikely to develop within the siliqua and thus the mechanism of dehiscence is most likely passive.