Triticeae Genomics and Genetics, 2025, Vol.16, No.2, 79-91 http://cropscipublisher.com/index.php/tgg 82 offered is that the chitinase gene alone already provided such a high level of resistance (nearly immune in some tests) that adding the AMP gene didn’t dramatically improve upon it. In other words, there might have been a ceiling effect where once you reach near-immunity with one strategy, adding another doesn’t show much additional benefit in measured outcomes. However, it’s worth noting that in conditions or diseases where chitinase alone might not give immunity, the combination could still prove more valuable. The lack of a statistically significant difference in this particular set of experiments doesn’t diminish the fact that both genes contributed to the overall resistance seen across different scenarios. The researchers also mentioned that they repeated key trials across multiple plant generations and in different locations, and the resistance traits held steady. This is important because it shows the trait is stable (the genes are inherited and expressed in subsequent generations) and robust across different environments. There was no sign that the resistance was a fluke of one generation or that it would break down under slightly different conditions. That stability is crucial if one were to consider developing a commercial variety - you want to ensure the resistance will persist. 6 Agronomic Performance Evaluation of Transgenic Barley 6.1 Growth traits Improving disease resistance is great, but not if it comes at the cost of poor growth or other problems. So, the study also paid close attention to the general growth and development of the transgenic barley to see if the foreign gene expression had any negative effects on normal plant growth. They systematically observed things like germination, seedling vigor, plant height, tillering (number of stems), and development timing in the transgenic lines compared to non-transgenic controls. First, at the seedling stage, they found no significant differences in how the transgenic seeds germinated or how the seedlings grew initially. The emergence rate of transgenic seedlings was around 96%, compared to 94% for controls - essentially the same (the slight difference was not statistically significant). The seedlings looked healthy and of similar quality in both groups. As the plants grew, they measured plant height and tiller number. By the late jointing stage, they noticed that some transgenic lines were just a little bit shorter than the control plants - about 2-4 cm shorter, which is less than a 5% difference in height (Boni et al., 2017). This is a minor difference and could be due to normal variation; it wasn’t large enough to be of practical concern. As for tillers, which are the shoots that can form grain heads, the transgenics had about the same number of effective tillers as the controls on average. In some transgenic lines, the tiller count even slightly exceeded the control. The authors speculate that maybe because the transgenic plants stayed healthier (less disease stress), they were able to support as many or more tillers. They observed the overall growth duration and found that the transgenic lines went through their life cycle in sync with the control. The time to heading (flowering) and maturity was virtually the same, with at most a two-day difference between transgenics and controls. This indicates that the insertion and expression of the antifungal genes didn’t disrupt the developmental timing - the plants weren’t delayed or sped up in their growth phases. They also looked at physiological indicators like leaf chlorophyll content and photosynthetic rates during the grain-filling period. They saw that the transgenic plants’ leaves stayed green and functional just as long as the control leaves did after heading. In fact, if anything, the transgenic leaves senesced (aged) slightly more slowly than the control leaves, although the difference was not statistically significant. This could be because the healthier, disease-free leaves in the transgenics were under less stress, but the key point is there was no adverse effect like premature aging of the plant due to the transgene. One observation was that a few transgenic lines, specifically those carrying both the chitinase and AMP genes, showed a very slight growth delay at the seedling stage. These lines were a bit slower to get started and were slightly shorter early on. However, this difference was temporary - after the jointing stage, these plants caught up
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