Internal phloem in an interspecific hybrid of cassava, an indicator of breeding value for drought resistance.

We examined the stem anatomy of Manihot esculenta Crantz and its hybrid with M. oligantha Pax. Cross-sections were stained with safranin-alcian blue. Manihot esculenta and its hybrid were found to have the same vascular structure in bicollateral bundles with internal phloem, which has been associated with drought resistance in other plant groups. If this association is established for cassava, it would facilitate the selection of lines that are more adapted to arid regions. This is the first report of internal phloem in this genus.