Apple (Malus domestica) is a delicious fruit of high economic value. However, numerous destructive fungi affect apples, greatly limiting their production. Many studies have shown that salicylic acid and jasmonic acid improve plant resistance to fungal diseases, but the potential mechanisms of cytokinin action and fungal diseases remain largely unreported. The IPT gene family encodes the proteins required for cytokinin biosynthesis and plays a central role in plant biological progresses. In our previous study, we found that the disease resistance in autotetraploid apple was much better than ‘Hanfu’ diploid and analyzed the transcriptome data between ‘Hanfu’ diploid and autotetraploid apple. We found that the MdIPT8 gene was significantly differentially expressed. Therefore, we focused on gene family functions in cytokinin biosynthesis and biotic stress responses. We identified ten IPT genes in the ‘Hanfu’ whole genome that are unevenly distributed across the five apple chromosomes. Phylogenetic analysis indicated that this gene family belonged to two groups. Transcriptional analysis of the ten IPT genes indicated that MdIPT8 could be induced under Colletotrichum gloeosporioides infection in apple leaves. The MdIPT8 protein, when fused to the green fluorescent protein, identified the chloroplast as the site of protein localization. Finally, we confirmed that overexpression of MdIPT8 increased the resistance of C. gloeosporioides infection. Taken together, we have identified that the endogenous cytokinin content of ‘Hanfu’ leaves increased during C. gloeosporioides infection and the application of exogenous cytokinin improved the resistance of apple leaves to C. gloeosporioides and found that MdIPT8 can increase apple anthracnose resistance by improving the biosynthesis of cytokinin.

苹果（Malus domestica）是一种具有很高经济价值的美味水果。然而，许多破坏性真菌会影响苹果，极大地限制了它们的生产。许多研究表明，水杨酸和茉莉酸可提高植物对真菌病害的抵抗力，但细胞分裂素作用和真菌病害的潜在机制仍未见报道。IPT基因家族编码细胞分裂素生物合成所需的蛋白质，并在植物生物学进程中发挥核心作用。在我们之前的研究中，我们发现同源四倍体苹果的抗病性明显优于‘汉服’二倍体，并分析了‘汉服’二倍体与同源四倍体苹果之间的转录组数据。我们发现MdIPT8基因显着差异表达。因此，我们专注于细胞分裂素生物合成和生物应激反应中的基因家族功能。我们在“汉服”全基因组中鉴定了 10 个IPT基因，这些基因在五个苹果染色体上分布不均。系统发育分析表明该基因家族属于两个群体。十个IPT基因的转录分析表明MdIPT8可以在苹果叶炭疽菌感染下被诱导。MdIPT8 蛋白与绿色荧光蛋白融合后，将叶绿体识别为蛋白质定位位点。最后，我们证实MdIPT8的过表达增加了抗性C. gloeosporioides感染。综上所述，我们发现'汉服'叶片的内源性细胞分裂素含量在C. gloeosporioides感染期间增加，并且外源性细胞分裂素的应用提高了苹果叶对C. gloeosporioides的抗性，并发现MdIPT8可以通过改善苹果炭疽病抗性来提高抗炭疽病的能力。细胞分裂素的生物合成。