This study was conducted during two consecutive seasons (2020 and 2021) in a plastic house located at the citrus seedling production unit of the Horticulture Research Institute, Agriculture Research Center, Giza Governorate, Egypt. To investigate the effects of different pre-sowing soak treatments on seed germination and growth performance of four citrus rootstocks: Rangpur lime (Citrus limonia L.), Carizzo citrange (Citrus sinensis Osb. X Poncirus trifoliate L.), Cleopatra mandarin (Citrus reshni L.) and sour orange (Citrus aurantium L.). Five pre-sowing treatments were applied by soaking rootstock seeds for 24 hours as follows: tap water (control), acetic acid at 1%, yeast extract at 1%, algae extract at 1%, and GA₃ at 20 ppm. The same five previous soaking treatments with the same doses were used as foliar treatments monthly until the grafting time.
The results revealed that the type of rootstock, pre-sowing treatment, and foliar fertilization significantly affected seed germination percentage and seedling attributes in both seasons. Concerning the effect of pre-sowing and foliar treatment, data showed that soaking seeds in acetic acid at 1% for 24 hours were more effective than other treatments in enhancing the germination percentage and all seedling traits, i.e., seedling height, number of leaves, root length, and number of roots. Regarding the effect of rootstock type, it was quite clear that sour orange rootstock significantly achieved the highest percentage of germination and all seedling characteristics.