Potential for gene transfer from Saccharum species (sugarcane)

Abstract

Trait development by genetic modification (GM) technology is viewed as complementary to traditional breeding programmes in the sugarcane industry. However, before commercial release of GM sugarcane, risk assessment studies are required to evaluate the potential impact of such crops on the environment. Unintentional transfer of the transgenes to related species is undesirable. The aim of the study was to assess the gene flow potential from sugarcane to wild relatives, by reviewing the literature around sugarcane hybridization and assessing pollen viability of commercial sugarcane varieties. A systematic literature study was conducted to identify species that are most likely to spontaneously hybridise with sugarcane. While neither interspecific nor intergeneric hybridization has been reported in the wild in South Africa, crosses under experimental conditions between sugarcane and related taxa have been carried out by breeders elsewhere in the world. Genera crossed with sugarcane include Bambusa, Imperata, Miscanthus, Saccharum and Sorghum. However, the putative hybrids generated are reported to be weak with slow growth rates and poor establishment. In the second part of the study, pollen viability was assessed from selected flowering sugarcane in plantations from the coastal regions of KwaZulu-Natal and in Mpumalanga. Pollen viability of up to 64% (determined using potassium iodide and triphenyl tetrazolium chloride stains and visualised microscopically) was observed in cultivar N36. It is therefore recommended for future studies to determine (a) the geographical proximity of related genera, (b) overlap of flowering times, and (c) pollen longevity, to determine the risk of GM sugarcane outcrossing with a related plant