Field Crop 2025, Vol.8, No.2, 93-101 http://cropscipublisher.com/index.php/fc 96 4.2 Molecular breeding technologies Breeding is different now, with the magic tool of marker-assisted selection (MAS). In 2024, Ricciardi's team found that it was very fast to use it to find gene loci such as Rpv36 and Rpv37 that are resistant to downy mildew. But being fast is not enough. Genomic selection (GS) is more powerful and can deal with multiple traits at once (Fang, 2024). Dry et al. (2010) predicted that combining traditional breeding with these new technologies is the best way. For example, the project done by Qiu et al. (2015) proved that grapes bred in this way can resist several diseases at the same time. 4.3 Gene-editing technologies The CRISPR/Cas9 technology, which has been very popular recently, has played a new trick in grape disease resistance. Wan et al. (2020) found that by cutting the VvMLO3 gene, the resistance of grapes to powdery mildew increased. Interestingly, the grapes treated in this way grew quite normal. The principle is that the pathogens cannot find a breakthrough point to attack, and the grapes can also produce defensive substances themselves. However, the disadvantage is that the operation is more delicate and not every laboratory can do it. 4.4 Exploration and utilization of resistant germplasm resources Did you know that many disease-resistant genes are actually "borrowed" from wild grapes. For example, against phylloxera, wild germplasm is a great savior. Agurto et al. (2017) conducted an interesting experiment: they combined the Run1 of wild species with the REN1 of cultivated species. As a result, the new variety cultivated had a particularly powerful defense system, which could produce a large amount of bactericidal substances and directly "starve" the bacteria to death. This also reminds us that it is really important to protect wild grape resources. Maybe one day we can find precious genes from them. 5 Interactions Between Grape Defense Mechanisms and the Environment 5.1 Combined effects of stresses When it comes to the defense system of grapes, it is actually quite complicated. You may not know that grapes often have to deal with pests and diseases and weather changes in the field at the same time, and the two will affect each other. Take powdery mildew for example. Grapes are originally resistant to this disease, but the situation changes when they encounter high temperature and drought. Roatti et al. (2013) conducted an experimentand found that high temperature or drought alone is not a big deal, but if both come together, the disease resistance of grapes will be significantly reduced. This is mainly because the leaves lack water, causing some disease resistance genes to not work properly. 5.2 Relationship between diseases and climate change Here is an interesting phenomenon: powdery mildew (caused by the fungus called Erysiphe necator) is more difficult to deal with under drought conditions. Zhou et al. (2024)'s study pointed out that drought can disrupt the hormone balance in plants, especially the two signaling pathways of salicylic acid and ethylene. You know, transcription factors such as VviWRKY10 and VviWRKY30 are supposed to help grapes resist powdery mildew, but once they encounter drought, they don't work well. Climate warming is really a big problem now. As the weather becomes more unstable, pathogens like Erysiphe necator have a better life. Agurto et al. (2017) found that powdery mildew may become more common and more serious. Fortunately, scientists have found some disease-resistant genes, such as Run1 and REN1. Combining these genes can make grapes more disease-resistant. Speaking of future research directions, Liu et al. (2024) proposed that we must first understand how the grape defense system and environmental changes affect each other. The new disease-resistant gene loci found through GWAS technology are very helpful for breeding new varieties. As Ricciardi et al. (2024) said, if we can know the resistance genes for downy mildew and powdery mildew in advance, we can breed grape varieties that are more adaptable to climate change.
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