bushy, a dominant pea mutant characterised by short, thin stems, tiny leaves and a major reduction in epical dominance

The spontaneous, single-gene dominant, pea (Pisum sativum L.) mutant bushy is characterised by short, thin stems, tiny leaves and a proliferation of b asal lateral branches. We symbolised the dominant mutant allele bsh and the recessive wild-type allele BSH, Some effects were very. large, e.g. the re duction in internode length was around 10-fold in pure mutant plants. The e ffect on branching was qualitative under our conditions as the wild-type di d not branch and the mutant branched extensively, Analysis of epidermal cel ls indicated the reduction in internode length arose principally from a red uction in cell length. The bushy mutation also altered root morphology with a reduction in the number and length of lateral roots. Time to first open flower was increased but node of flower initiation was not affected, In a f ew cases, bushy plants died before producing an open flower even though tin y abortive flower buds were produced in the upper leaf axils. In pure mutan t plants, individual seed weight mas reduced by 30%, number of seeds per po d was reduced 3-fold, and seed number per plant was reduced 4-fold, However , pod size was essentially normal for a given seed content, and the flowers were fertile and of normal structure. Grafting studies showed the primary action of the bushy, mutation occurred in the shoot, In summary, the reduce d cell and shoot elongation, loss of apical dominance and a primary action in the shoot, all point toward auxin deficiency (or perceived deficiency) a s a possible cause of the bushy phenotype. The overall characteristics of b ushy make it a useful mutant for research on plant development.