Triticeae Genomics and Genetics, 2025, Vol.16, No.2, 79-91 http://cropscipublisher.com/index.php/tgg 86 of disease resistance. We observed only extremely minor and rare effects (such as minor leaf tip necrosis in a few cases) that were not considered problematic. This comprehensive evaluation addresses potential concerns and demonstrates that the disease resistance modification did not inadvertently render the barley "unhealthy" in any other way. 7 Case Studies 7.1 Japan’s NARO: barley with a chitinase gene for Fusarium resistance The National Agriculture and Food Research Organization (NARO) in Japan has been working on genetically engineered solutions to Fusarium head blight (FHB), a notorious fungal disease that affects barley (and wheat) by infecting the grain heads. FHB, caused by Fusarium species, not only reduces yield but also contaminates grain with mycotoxins like DON. The NARO researchers took a chitinase gene (which we know is a PR protein that attacks fungal cell walls) from barley itself and introduced it into barley (and also into wheat) using a biolistic (gene gun) method. By using barley’s own gene (a class II chitinase, which is a PR3-type protein) and putting it into barley and wheat, they created transgenic plants that produce extra chitinase. In field inoculation trials, the transgenic barley with the chitinase gene showed remarkable resistance to Fusarium head blight (Shin et al., 2008). When Fusarium spores were sprayed onto the ears, the transgenic barley had very little disease. Only a few spikelets (florets) on an ear would show infection, and those didn’t spread or cause the whole head to rot. The grain set and filled normally in the transgenic plants. In contrast, the conventional (non-transgenic) barley in the same test got widespread infection across the ears, leading to rotten patches on the heads and a lot of shriveled, light-weight grains. Most importantly, they measured the content of DON (deoxynivalenol, a vomitoxin produced by Fusarium) in the harvested grains. In the transgenic barley grain, DON levels were more than 80% lower than in grain from the susceptible control. In many transgenic grain samples, DON was essentially undetectable. This is a critical result because in Fusarium infestations, often the yield loss is one issue but the safety of the grain is another. The transgenic barley’s ability to prevent DON accumulation means the grain is much safer for food or feed. This Japanese NARO study demonstrated that expressing a single antifungal gene (chitinase) can make barley highly resistant to Fusarium head blight. It not only suppressed the disease symptoms but also the toxin that comes with the disease. Because chitinase breaks down fungal cell walls, it likely halted the fungus’s progress early, thus also preventing it from synthesizing much toxin. They also noted that the chitinase-expressing plants showed a degree of enhanced resistance to other diseases. For example, in greenhouse tests with multiple pathogens, those transgenic barley (and wheat) plants were better at fending off not just Fusarium but also some foliar diseases like powdery mildew. That makes sense because chitinase can act broadly against many fungi (any fungus that has chitin in its cell wall could potentially be affected). The implications of this are huge especially for crops like wheat, which lack strong native resistance to Fusarium head blight. Introducing a barley gene into wheat (or barley) gave them a powerful tool to combat a disease that traditional breeding hasn’t solved (wheat doesn’t have highly FHB-resistant varieties). NARO is taking this further by incorporating the chitinase transgene into their breeding programs to create new barley lines that are both Fusarium-resistant and agronomically competitive. They are evaluating important traits like agronomic performance (yield, growth) and malting/brewing quality in these lines. According to their reports, the transgenic barley with the chitinase gene had similar agronomic traits to the normal variety - meaning it grew and yielded similarly, with no negative effects - which is encouraging for commercialization. The fact that barley’s own gene was used and yet it could protect wheat too is interesting; it shows a cross-application (“cross-species disease resistance”) - barley and wheat are different species, but a defense from one can work in the other. NARO’s success shows that by focusing on key defense proteins (like chitinase), we can engineer cereals to resist diseases that their inherent genetics couldn’t handle well. It’s an important
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