Numerous Cucurbitaceae species are seriously threatened by the hemibiotrophic oomycetes with a severe negative impact on plant yields. In particular, Phytophthora melonis causes severe symptoms that significantly reduce cucumber productions. However, there is currently little known about the Cucurbita pepo-P. melonis interaction. This study analyzed enzymatic activity of defense-related antioxidant enzymes peroxidase (POX), superoxide dismutase (SOD), polyphenol oxidase (PPOs), catalase (CAT); hydrolytic enzymes- β-1,3-glucanase; phenylalanine ammonia-lyase (PAL) and phenolic content in two resistant pumpkin “Tanbal” and “Ghelyani” and two susceptible, “Marmai” and “Khoreshti”, in response to Phytophthora blight disease (PBD), caused by Phytophthora melonis over the time courses of 24, 48 and 72 h post inoculation (hpi). All enzymes were highly up-regulated in the resistant C. pepo accessions “Tanbal” and “Ghelyani” inoculated with P. melonis. The mean level of enzyme activity varied from 1.3 to 6-fold higher in the resistant genotypes, of which SOD was increased by 6-fold, followed by PPOs and PAL 5.3-fold in comparison to untreated controls. Conversely, the lower or negative expression of these enzymes was observed in susceptible pumpkins. The highest β-1,3-glucanases activity, marker of salicylic acid pathway, was recorded in resistant “Tanbal” with 3-fold increase, followed by 2.4-fold increase in Ghelyani 24 hpi following inoculation which shows the involvement of salicylic acid (SA)-mediated defense. Furthermore, significantly higher activities of the ROS-scavenging-defense-enzymes CAT (1.6-fold), and POX (6-fold), CAT (6-fold (, and POX (6-fold) were observed in the roots of resistant-cultivars at different-wpis, compared with non-inoculated-controls. We also analyzed the quantitative-gene-expression-changes of three-candidate-gene-markers; PR-1, POD and WRKY21 by qRT-PCR along the related time-courses revealed the considerable transcriptomic-response in the resistant-genotypes, 1.1–2.7-fold in the roots and leaves, respectively. Surprisingly, PR-1-gene-marker, basically resistant to wilting agent- Verticillium dahlia was overexpressed in resistant “Tanbal” and “Ghelyani” against P. melonis. Similar results were obtained on POD-gene-marker resistant to powdery mildew, Podosphaera xanthii that similarly modulates immunity against P. melonis. There was also a highly significant correlation between the related enzymes and gene-markers, predominantly between PPO-enzyme and PR-1, POD and WRKY21; r = 0.851**r = 0.878** and r = 0.866**, followed by PAL and SOD respectively. Thus, molecular pathways associated to P. melonis resistance may be considered as future targets for manipulation in the development of resistant cultivars.

许多葫芦科物种受到半生物营养卵菌的严重威胁，对植物产量产生严重的负面影响。特别是，瓜疫霉会引起严重的症状，从而显着降低黄瓜产量。然而，目前人们对西葫芦与甜瓜之间的相互作用知之甚少。本研究分析了防御相关抗氧化酶过氧化物酶（POX）、超氧化物歧化酶（SOD）、多酚氧化酶（PPO）、过氧化氢酶（CAT）的酶活性；水解酶-β-1,3-葡聚糖酶；两种抗性南瓜“Tanbal”和“Ghelyani”以及两种易感南瓜“Marmai”和“Khoreshti”中的苯丙氨酸解氨酶（PAL ）和酚含量，以应对由瓜疫霉引起的疫霉病（PBD ）接种后 24、48 和 72 小时的疗程 (hpi)。在接种了甜瓜的抗性C. pepo品种“Tanbal”和“Ghelyani”中，所有酶均高度上调。与未处理的对照相比，抗性基因型的酶活性平均水平高出 1.3 至 6 倍，其中 SOD 增加了 6 倍，其次是 PPO 和 PAL 增加了 5.3 倍。相反，在易感南瓜中观察到这些酶的表达较低或呈负表达。最高的β-1,3-葡聚糖酶活性（水杨酸途径的标志物）在抗性“Tanbal”中记录到增加了 3 倍，随后在接种后 24 hpi 的 Ghelyani 中增加了 2.4 倍，这表明水杨酸的参与（ SA）介导的防御。此外，在抗性植物的根部观察到ROS清除防御酶CAT（1.6倍）和POX（6倍）、CAT（6倍）和POX（6倍）的活性显着升高。 -与未接种对照相比，不同 wpi 的品种。我们还通过 qRT-PCR分析了三个候选基因标记的定量基因表达变化； PR-1、POD和WRKY2 1时间进程揭示了抗性基因型中相当大的转录组反应，在根和叶中分别是 1.1-2.7 倍。令人惊讶的是，PR-1 -基因标记，基本上对萎蔫剂 -黄萎病在抗性中过度表达“Tanbal”和“Ghelyani”针对甜瓜疫病菌。在抗白粉病的POD基因标记上也获得了类似的结果， Podosphaera xanthii也同样调节针对甜瓜疫病菌的免疫力。相关酶与抗白粉病菌之间也存在高度显着的相关性。基因标记，主要在 PPO 酶和PR-1、POD和WRKY21 ; r = 0.851**r = 0.878** 和 r = 0.866**，随后分别是 PAL 和 SOD。因此，与甜瓜疫病抗性相关的分子途径可能被认为是抗性品种开发的未来操纵目标。