Drought tolerant stem anatomy characteristics in Manihot esculenta (Euphorbiaceae) and a wild relative.

The stem structure of two cassava cultivars, UnB 99 and UnB 110, known for being adapted to humid conditions and tolerant to drought, respectively, and of a wild species, Manihot glaziovii, was examined anatomically. Free-hand sections of secondary stems were made, clarified with 50% sodium hypochlorite solution, stained with 1% alcian-blue safranin, and then passed through an ethanol series and butyl acetate, followed by mounting in synthetic resin. M. glaziovii stems had dense prismatic and druse crystals in the cortical parenchyma, along with abundant gelatinous fibers. The pericycle fibers also had thicker walls. An absence of crystals, offset by abundant starch, was observed in clone UnB 99. In M. glaziovii, abundant tyloses were found in vessel elements; these were rare in clones UnB 99 and UnB 110. The wild species had larger vascular vessels; the secondary xylem showed very little starch, unlike UnB 99 and UnB 110. In clone UnB 110, starch was observed in the cortical region, and medulla and gelatinous fibers were found in the pericycle and secondary xylem. Brown stem color was found to be associated with tolerance to drought.

Compatibility of interspecific Manihot crosses presaged by protein electrophoresis .

Cross incompatibility of wild Manihot species with cassava (M. esculenta) can impede their utilization for improving this cultigen. We tested whether compatibility could be determined based on electrophoresis results. Manihot pilosa, M. glaziovii, M. reptans, and M. cearulescens were tested. These species were allowed to hybridize with cassava to determine whether hybridization coincides with the similarity index based on electrophoresis analysis. Gene markers of leaf shape, stem surface, disk color, and fruit shape were used to confirm hybridization. Manihot pilosa and M. glaziovii successfully hybridized with cassava, while the others failed to do so under natural conditions. This result coincided with the similarity index from electrophoresis.