PARENT SESSION
Posters P4B Sugar signalling: Photosynthesis, hormones and development. Abstracts (480-527)

Does externally supplied sucrose act as an alternative to photosynthates or a signal which can alleviate root growth failure in the common bean (Phaseolus vulgaris L.) dwarf plants? Muhammad Iqbal^*,1, Evangelos Leonardos¹, Bernard Grodzinski¹, ¹ Department of Plant Agriculture, Guelph, ON, Canada

ABSTRACT- Dwarfing in common beans can result from the action of the semi-dominant alleles DL₁ and DL₂ at two complementary loci, which are expressed in the root and shoot, respectively. The DL genotypes can also be simulated using grafting techniques. Seedlings of Phaseolus vulgaris cultivars Carioca (Ca, genotype DL₁DL₁dl₂dl₂) and Prelude (Pd, dl₁dl₁DL₂DL₂) were used. Self-grafts (Ca/Ca and Pd/Pd) and Ca/Pd (DL₁DL₁dl₂dl₂/dl₁dl₁DL₂DL₂, scion/rootstock) have normal growth whereas Pd/Ca (dl₁dl₁DL₂DL₂/DL₁DL₁dl₂dl₂) fails to grow after graft healing. Lethal dwarfing and the analogous lethal graft combination Pd/Ca are specifically associated with a failure of root growth. This system may offer opportunities to study fundamental mechanisms of source and sink relationships. Root growth was observed in both lethal dwarfs and lethal graft combinations after the addition of sucrose to the MS growth medium. When these lethal dwarfs and grafted plants were transplanted into solution culture without sucrose, there was no new root growth and the existing root system died. These data and ¹⁴C-partitioning studies were used to test the hypothesis that failure of root growth may be a consequence of photosynthate deprivation of the roots due in part to signaling incompatibilities between the genotypes.

KEY WORDS: DL-gene system, Phaseolus vulgaris, root shoot partitioning, sugar signalling