Field Crop 2025, Vol.8, No.2, 93-101 http://cropscipublisher.com/index.php/fc 94 loves living tissue. You will see the characteristic white powder on leaves, stems and fruits, especially in warm and humid seasons, and it spreads at an alarming rate (Gadoury et al., 2012; Weng et al., 2014). However, in terms of the degree of damage, gray mold is not much less, especially in rainy areas. Speaking of gray mold, the pathogen Botrytis cinerea is much more cunning. It kills plant tissue first and then slowly eats it-a typical "carrion-eating" fungus. It is most dangerous when the fruit is about to mature, not only reducing production but also affecting quality (Kelloniemi et al., 2015). By the way, the Malviya et al. (2022) developed a powdery mildew severity scoring system, which is very helpful for breeding disease-resistant varieties (Figure 1). In addition to these, fungal diseases such as black rot are also a headache. Usually, they are prone to outbreaks when the weather is hot and humid. Now they are mainly dealt with by spraying pesticides and cultivating disease-resistant varieties (Qiu et al., 2015). Figure 1 Pictorial depiction of 0~4 rating scale for powdery mildew disease severity (Adopted from Malviya et al., 2022) 2.2 Pests Speaking of insect pests, phylloxera is a tough guy, specifically eating grape roots, and in severe cases, the entire plant will die. European grapes (Vitis vinifera) are particularly susceptible to the disease, and now resistant rootstocks are often used to prevent it (Fedorina et al., 2022). 2.3 Viral diseases In terms of viral diseases, leaf curl virus is quite common. The leaves will change color and the quality of the fruit will deteriorate. It is mainly spread by mealybugs. There is also a red spot virus, which will cause red spots on the leaves and late ripening of the fruit. These two viruses cannot be cured now, and they mainly rely on controlling the spreading insects and cutting down the diseased plants (Fedorina et al., 2022). Massonnet et al (2022)’s study showed that poor management of these diseases can really seriously affect the harvest. 3 Defense Mechanisms of Grapes Against Biotic Stresses 3.1 Innate immune response In fact, many plants have this ability-those special receptors (PRRs) on the surface of grape leaves can recognize the molecular characteristics of pathogens (PAMPs). Santos et al. (2020) conducted an experiment and found that when downy mildew was first infected, grapes would quickly adjust a bunch of defense-related proteins. However, this first line of defense (what experts call PTI) is sometimes not very reliable. For example, the Roatti et al. (2013) found that although the use of biological pesticides such as Trichoderma can strengthen defense, the effect is discounted when encountering drought or something. 3.2 Specific immune response Speaking of this, we have to mention the R gene-equivalent to the "special forces" of grapes. Fröbel et al. (2019) found that grapes with the Rpv10 gene would quickly activate dozens of defense genes when encountering downy mildew. Recently, Ricciardi et al. (2024) also found several new disease resistance gene clusters. Of course, scientists are not idle now. For example, the Capriotti et al. (2020) tried to use genetic modification technology to make these genes more active, but whether this method can be effective in the long run remains to be seen.
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