Enhancing cassava reproductive development does not negatively impact shoot to root ratio and dry matter content in storage roots

Abstract

From previous studies we developed treatments that significantly improved cassava female flower and fruit development, using a combination of the anti-ethylene, silver thiosulfate (STS), and the cytokinin, benzyladenine (BA); collectively referred to as plant growth regulators (PGR). In this study, we investigated whether the benefit derived from this treatment altered partitioning of photosynthate to other sinks and general vegetative growth of cassava in the first six months of plants growth, when reproductive growth initiates and peaks. Our flower enhancing treatment did not significantly alter shoot and storage root fresh weight, partitioning index on a fresh weight basis and percent dry matter content of storage roots between Months 2 and 5. With the onset of the dry season in Month 6, PGR treated plants had higher shoot and storage root fresh weight than controls but these plant parts responded proportionally and so partitioning index between controls and treated plants was not significantly different. The nighttime starch export under PGR treatments was reduced at Months 2, 4 and 5 but this was not correlated with flower development at these months. The survival of PGR treated plants until harvest was however reduced owing to increased mortality arising from phytotoxicity and increased susceptibility to disease. We therefore conclude that PGRs have effects more directly on flower and fruit reproductive signaling and regulatory pathways rather than on an indirect effect on resource partitioning.