Lupin mutants

There are ample a priori reasons to suspect that different plants of a single species may elaborate different amounts of alkaloids. It is well known that strains of tobacco and of lupines can be selected to yield greater or lesser amounts of alkaloids. That mutants occur is also highly probable. In this connection it is not unreasonable to suspect that the opium poppy may in fact be a mutant which was selected and cultivated because of its unique alkaloids. Neither morphine nor codeine have been found in any other species of Papaver and the basic ring system in these alkaloids has been found in part only in alkaloids derived from plants of a family (Menispermaceae) whose affinities with Papaveraceae can only be remote. 

Figure 2.2. Schematic illustration of the pathways for alkaloid synthesis in a bitter (wild type) form (1) of lupines and in two different sweet mutants (2 and 3). The pathways are depicted as two parallel lines since in a plant usually two sets of genes are operating. The x indicates the blocked reaction in the sweet form. In the Fi generation of the cross between 2 and 3, i.e., 4, the biosynthetic pathway is regained, and the resulting plant is bitter. In crosses involving a bitter form and a sweet form the Fi generation is always bitter (5 and 6). In 7 there is a double recessive homozygote, and when these plants are crossed with either 2 or 3 only sweet plants are produced (Nowacki, 1966). Courtesy of the journal.

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