Testing Transgenic Aspen Plants with bar Gene for Herbicide Resistance under Semi-natural Conditions

Abstract

Obtaining herbicide resistant plants is an important task in the genetic engineering of forest trees. Transgenic European aspen plants (Populus tremula L.) expressing the bar gene for phosphinothricin resistance have been produced using Agrobacterium tumefaciens-mediated transformation. Successful genetic transformation was confirmed by PCR analysis for thirteen lines derived from two elite genotypes. In 2014–2015, six lines were evaluated for resistance to herbicide treatment under semi-natural conditions. All selected transgenic lines were resistant to the herbicide Basta at doses equivalent to 10 l/ha (twofold normal field dosage) whereas the control plants died at 2.5 l/ha. Foliar NH4-N concentrations in transgenic plants did not change after treatment. Extremely low temperatures in the third ten-day period of October 2014 revealed differences in freeze tolerance between the lines obtained from Pt of f2 aspen genotypes. Stable expression of the bar gene after overwintering outdoors was confirmed by RT-PCR. On the basis of the tests, four transgenic aspen lines were selected. The bar gene could be used for retransformation of transgenic forest trees expressing valuable traits, such as increased productivity.

Does Acid Rain Alter the Leaf Anatomy and Photosynthetic Pigments in Urban Trees?

“…Previous studies found that the intensity of leaf damage depends on the concentration of the sprinkled acids [16,18,30,31,34], in which visible damage appears when acidity is below pH 3. The damages we found in the leaves of L. styraciflua at pH 2.5, were the necrosis of tissue forming spots in the intercostal area, some distorted margin areas, similar to those found in transgenic Populus tremula (Salicaceae) and Betula pubescens (Betulaceae), in which their resistance to the herbicide phosphinothricin was tested [35,36]. Another found alteration was the abscission of some leaves; this is consistent with previous reports for this species at pH 3 [37].…”

Effect of Phosphinothricin on Transgenic Downy Birch (Betula pubescens Ehrh.) Containing bar or GS1 Genes

“…In our work, all transgenic and control birch lines had a similar initial level of ammonium-an average of 9-13 µg/g of fresh weight. In our other study of two aspen genotypes and the transgenic lines obtained from them with the bar gene also did not significantly differ in ammonium content, but they contained it almost twice as much as birch saplings-on average 18-24 µg/g fresh weight [30]. At the same time, cotton plants with the pat gene contained three times more ammonium than the control non-transgenic cotton [40] and rice plants with the OsGS1;1 and OsGS2 genes contained three times less ammonium than the control non-transgenic rice [39].…”

“…We are unaware of any other previously published study on the transgenic herbicide-tolerant birch saplings, but other woody species containing the bar gene such as Populus spp. [28][29][30] and Eucalyptus camaldulensis [31] demonstrated similar levels of tolerance sufficient for their commercial use. Minor symptoms of the lesion were observed mainly on the apical leaves.…”

“…In the two-year-old birch saplings, leaf necrosis developed somewhat more slowly compared to the one-year-old plants in our study (Tables 1 and 2). It should be noted that the wild-type Betula pubescens plants were less sensitive to PPT than Populus tremula plants-complete leaf necrosis was observed in birch saplings after seven or more days, while in aspen plants, complete leaf necrosis occurred three days after being treated with the same doses of herbicide treatment [30].…”

“…There are only a few studies to assess the level of ammonium in plants with the GS gene after PPT treatment [30,39]. Treatment of birch saplings containing the GS gene using the 1% herbicide solution caused the same increase in the ammonium levels, as in the non-transgenic control species, but a lower dose increased the ammonium level insignificantly.…”