Stability of Gene Expression and Agronomic Performance of a Transgenic Herbicide-Resistant Sugarcane Line in South Africa

Abstract

Sugarcane (Saccharum hybrid) cultivar NCo310 was transformed with the pat gene, which confers resistance to the herbicide Buster (glufosinate ammonium; Bayer CropScience, Monheim am Rhein, Germany). The effect of the expression of this gene on the agronomic performance of a successful transgenic line, 22.2, was investigated. Field testing showed that the pat gene was stably expressed during three rounds of vegetative propagation. Morphological and agronomic characters such as stalk height, diameter, population, fiber, disease resistance, and yield, measured in the first ratoon, were not significantly different in the transgenic line and its untransformed counterpart. Of four weed treatments applied to transformed and untransformed plots, there were two scenarios in which significantly higher yields were observed: (i) untransformed cane treated using the conventional (non-Buster) herbicide protocol, widely used for weed control in the South African sugar industry, and (ii) transformed cane treated with a conventional preemergence cocktail, followed by two 5-L ha−1 Buster applications. However, the most economical weed control treatment is dependent on the cost of the herbicide to which resistance has been engineered. Buster currently costs (in South African Rand) ZAR150 (≈US $14.01) L−1 For Buster treatments to be cost effective for commercial growers, the price would have to be considerably lower. However, since hand-hoeing is deleterious to the cane, small-scale growers currently controlling weeds manually would find herbicide use an advantage. If they were to adopt transgenic sugarcane, Buster costs would need to be reduced only slightly for them to increase their returns.