Fruit shape index (round shape) and seed size have important effects on pumpkin yield. To investigate these traits and to create the most desirable state, a cross was made between two pumpkin cultivars. This study aimed to estimate the main gene effects (additive, dominant and di-genic epistasis) and to determine the mode of inheritance for fruit shape and seed size by generation mean analysis. Six generations, namely P₁, P₂, F₁, F₂, BC₁, and BC₂ from a cross between Zucchini and hull-less seed Pumpkin, S10 × P25, were constructed and evaluated for fruit length, fruit width, fruit shape index, and some seed-related traits (seed length, seed width, and seed thickness). The experiment was conducted in the research field of the Faculty of Agricultural Science, University of Guilan, Rasht, Iran in 2019. Results showed a significant difference between generations in terms of fruit and seed traits. Scale and joint scale tests showed the presence of epistasis for some traits. According to the results of the average traits of different generations, standard heterosis and hetrobeltiosis were observed. Concerning the fruit shape index and seed width, there was a dominance effect. The broad-sense heritability of the traits was relatively high for all traits and between 52 and 94%. Narrow sense heritability was between 26 and 90% and relatively low for the fruit shape index and seed width. Therefore, selection of elite lines and production of their hybrids are recommended as two methods suitable for breeding to achieve a round shape index and a larger seed size.

果实形状指数（圆形）和种子大小对南瓜产量有重要影响。为了研究这些特性并创造最理想的状态，在两个南瓜品种之间进行了杂交。本研究旨在估计主要基因效应（加性、显性和双基因上位性），并通过世代平均分析确定果实形状和种子大小的遗传模式。六代，即P ₁、P ₂、F ₁、F ₂、BC ₁和BC ₂从西葫芦和无壳种子南瓜 S10 × P25 之间的杂交中构建并评估果实长度、果实宽度、果实形状指数和一些种子相关性状（种子长度、种子宽度和种子厚度）。该实验于2019年在伊朗拉什特市桂兰大学农业科学学院的研究领域进行，结果表明，在果实和种子性状方面，世代之间存在显着差异。量表和联合量表测试显示某些性状存在上位性。根据不同世代平均性状的结果，观察到标准杂种优势和异种优势。关于果实形状指数和种子宽度，存在优势效应。这些性状的广义遗传力在所有性状中都较高，在 52% 至 94% 之间。狭义遗传力在 26% 到 90% 之间，果实形状指数和种子宽度相对较低。因此，推荐选择优良品系和生产它们的杂种作为两种适合育种的方法，以实现圆形指数和更大的种子大小。