Development of an in vitro pod culture technique for young pods of Phaseolus vulgaris L.

A research program to develop an in vitro culture technique adapted to very immature Phaseolus zygotic embryos indicated that osmolality within young pods in vivo ranged from 580 to 350 mosm during the first 10 d after pollin ation. Different culture techniques for 2-d-old Phaseolus pods are describe d using a modified Phillips medium for maturation. The application of high and variable osmolality conditions, similar to what is observed in vivo, du ring pod culture (1 wk) and before extracting the embryos, gave the best re sults in terms of ovule and embryo development. To solve contamination prob lems affecting pod development during these investigations, a sterilizing t echnique was tested combining various concentrations of polpoxyethylenesorb itan monolaurate (Tween 20) and a broad-spectrum industrial biocide, Plant preservative Mixture (PPM). The PPM sterilizing method totally eliminated p od contamination and did not affect ovule growth, but significantly reduced the embryo germination rate.