Growth, development and yield of transgenic 35S-thaumatin II-expressing cucumber plants – open field evaluation

Abstract

Transgenic cucumber plants (line 210, 225, 212, 224) expressing the thaumatin II transgene of three subsequent generations (T5, T6, T7) were cultivated in open field trials (N: 52°9’34.94”; E: 21°6’22.8”) for three seasons (2005, 2006, 2007) to establish if they perform equivalently to their non-transgenic counterpart – Borszczagowski inbred line of Cucumis sativus L. (line B). In each season, chosen phenotypic (stem length, leaf number, leaf area) and agronomic (dynamics of yielding, total yield) characteristics as well as weather conditions were analysed. Additionally, using immunoblotting, the presence of the sweet protein – thaumatin II in fruits of various classes was assessed. It has been shown that under open field conditions, the presence of the thaumatin II transgene does not limit transgenic plant performance of subsequent progenies, with the exception of line 224. The reduced growth and development of plants of line 224 most probably decreased their yielding potential. Total yield of other transgenic lines (210, 225, 212) and the non-transgenic line B was comparable, however yield variation was strongly defined by weather conditions that were far from optimal over the three seasons (2005–2007). Clearly, whereby the mean temperature of the fruiting period was higher than the multi-annual mean, the total yield of cucumber lines was relatively weakly related to the line and monthly mean temperature, yet strongly defined by monthly total precipitation. As transgenic cucumber fruit maturity progressed, thaumatin II protein accumulated in the fruit.