Triticeae Genomics and Genetics, 2025, Vol.16, No.2, 79-91 http://cropscipublisher.com/index.php/tgg 84 They also conducted an interesting test under high nitrogen fertilizer conditions. Often, if plants have hidden weaknesses, they might show up under stress or high input conditions. They wanted to see if the transgenics could utilize nutrients as effectively as controls. They observed that as they increased nitrogen fertilization, both transgenic and control plants showed the expected yield component responses (e.g., more grains per spike, heavier grains up to a point) and the transgenic lines responded just like the controls. They did not see any anomaly like the transgenics failing to take advantage of more fertilizer or, say, becoming more prone to lodging (falling over) under high fertility (excessive growth can cause lodging, but that didn’t happen disproportionately in the transgenics). The transgenic barley was able to fully utilize high nitrogen without any issues such as “excessive greening”. So nutrient response was normal. They also looked at grain quality parameters like crude protein and starch content of the grains. The crude protein content in the transgenic lines was slightly lower than the control (by about 0.5% to 2.4%, depending on the line). However, this still fell within the normal range of variation one might see due to environmental effects or different varieties. Starch content and other quality metrics didn’t show significant differences. A small drop in grain protein could simply be due to a dilution effect if yield (starch) went up a bit, or perhaps because the antifungal proteins made up a small part of the total protein (which might slightly alter the measured crude protein percentage). But again, these differences were minor and within normal fluctuation. Crucially, there was no significant yield penalty associated with the disease resistance trait. In disease-free conditions, the transgenic barley basically yielded the same as conventional barley. In disease conditions, one would expect the transgenics to actually yield more because they would lose less to disease (though these particular controlled trials didn’t explicitly measure yield under diseased vs. protected conditions, one can infer yield would be better for transgenics in a real disease epidemic). This aligns with many reports in other crops where introducing disease resistance helps protect yield (by reducing losses), and if the gene itself doesn’t cause problems, yield in absence of disease stays normal (Horvath et al., 2001). In our case, the transgenic barley had minimal yield loss even when there was no disease, and in the presence of disease pressure, it maintained yield much better than diseased controls - in fact likely resulting in higher realized yield because the control would suffer while the transgenic thrives. They do note that more multi-year, multi-location field trials would be ideal to fully confirm these yield and quality outcomes. But overall, the evidence so far indicates that the disease-resistant transgenic barley performs on par with standard barley in yield and grain quality. There’s no trade-off like “you get resistance but you lose yield” - which is an extremely important validation for the practicality of this approach. 6.3 Evaluation of fitness cost or abnormal phenotypes Whenever we introduce new genes, especially ones related to defense (which can sometimes trigger stress responses), it’s important to check for any unintended “fitness costs” or abnormal traits. The study carefully evaluated whether the transgenic barley had any such issues. They looked at general plant morphology and found that the transgenic barley had a normal appearance. Plant architecture (height, leaf shape, ear type) was consistent and comparable to the control. They did not observe abnormalities like dwarfism, distorted organs, leaf lesions, or color variegation in the transgenic lines. This is reassuring because sometimes the expression of foreign genes can unintentionally affect development, but that didn’t happen here. Overexpression of some resistance genes in other cases has led to things like premature senescence or spontaneous leaf necrotic spots (this is often referred to as the “fitness cost” of resistance, where the plant’s immune system being constantly active can slightly damage the plant itself). In our transgenic barley, they saw only a very minor instance of this: a few plants with extremely high chitinase expression showed some mild necrotic streaks at the leaf tips during the grain-filling stage (milky stage of the grain). This was a very low-frequency occurrence and when it happened, it was just the very tip of the leaf and did not affect the overall leaf health or photosynthesis substantially. They note that this kind of leaf tip necrosis is actually a known
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