Grafting is widely used in cucumbers to enhance their tolerance to environmental stress. Compatibility is a key factor for successful grafting, however, the physiological mechanisms that affect grafting compatibility are not clear. This study aimed to investigate the physiological mechanism underlying cucumber/pumpkin grafting compatibility. Two pumpkin cultivars with significant differences in compatibility, Figleaf gourd (compatible rootstock, Cf) and Dongyangshenli (incompatible rootstock, Cmo), were used as rootstocks. Three cucumber cultivars with different growth rates were used as scions, including cucumber ‘Shenluchunsi’ (strong growth, V1), ‘Cuilü’ (weak growth, V2), and ‘Liangyoulüjian 102’ (medium growth, V3). Six grafting combinations (V1/Cf, V2/Cf, V3/Cf, V1/Cmo, V2/Cmo, and V3/Cmo) were used to analyze the effect of scion and rootstock varieties, as well as the chemical composition of the exudate from the stem cutting surface, on the compatibility of grafted plants. Here, we found that rootstock was closely correlated with the compatibility of cucumber/pumpkin grafted plants. The sucrose content in the exudate of the stem, enzyme activity, and the expression of genes related to sucrose biosynthesis in Cmo were significantly higher than those in Cf. Correlation analysis showed that the sucrose content difference between the exudate of rootstock and scion stems was negatively correlated with graft compatibility. Exogenous treatment with a 0.5 % sucrose solution on the scions significantly reduced the difference in sucrose content between rootstock and scion and enhanced graft survival rate in the incompatible combination. The stem segment grafting experiment in vitro found that the high difference in sucrose concentration between the rootstock and scion decreased the grafting compatibility of cucumber/pumpkin by reducing the adhesion of the cutting surface. Taken together, the higher sucrose concentration difference between rootstock and scion decreased the adhesion of the cutting surface, resulting in the incompatibility of cucumber/pumpkin grafted plants.

中文翻译：

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接穗和砧木之间蔗糖浓度的差异影响黄瓜/南瓜嫁接植株的不亲和性


嫁接广泛用于黄瓜，以提高它们对环境压力的耐受性。相容性是成功接枝的关键因素，然而，影响接枝相容性的生理机制尚不清楚。本研究旨在探讨黄瓜/南瓜嫁接相容性的生理机制。以无花果叶葫芦（相容砧木，Cf）和东阳神里（不相容砧木，Cmo）两个相容性差异显著的南瓜品种为砧木。以3个不同生长速率的黄瓜品种为接穗，包括'神鹿春丝'（强势生长，V1）、'翠禄'（弱生长，V2）和'良友绿剑102'（中等生长，V3）。采用 6 种嫁接组合 （V1/Cf、V2/Cf、V3/Cf、V1/Cmo、V2/CMO 和 V3/Cmo） 分析接穗和砧木品种以及茎切割表面分泌物的化学组成对嫁接植物相容性的影响。在这里，我们发现砧木与黄瓜/南瓜嫁接植物的相容性密切相关。茎分泌物中蔗糖含量、酶活性和 CMO 中蔗糖生物合成相关基因的表达显著高于 Cf。相关性分析表明，砧木和接穗茎分泌物的蔗糖含量差异与嫁接相容性呈负相关。在不相容组合中，用 0.5 % 蔗糖溶液对接穗进行外源处理可显著降低砧木和接穗之间蔗糖含量的差异，并提高嫁接成活率。 体外茎段嫁接实验 发现，砧木与接穗之间蔗糖浓度的高差异通过减少切割面的粘附性，降低了黄瓜/南瓜的嫁接相容性。综上所述，砧木和接穗之间较高的蔗糖浓度差异降低了切割表面的粘附性，导致黄瓜/南瓜嫁接植株的不相容性。