Study on the effects of pollen sources on the agronomic, biochemical, mineral, and pomological traits of date palm (Phoenix dactylifera L.) cv

Genet Resour Crop Evol https://doi.org/10.1007/s10722-024-01885-9 RESEARCH ARTICLE Study on the effects of pollen sources on the agronomic, biochemical, mineral, and pomological traits of date palm (Phoenix dactylifera L.) cv ’Deglet Nour’ fruits in Degache Oases (Tunisia) Karim Kadri · Monia Jemni · Mohammed Mesnoua · Shyam Sundar Sharma · Anoop Anand Malik · Souhayla Makhlouf · Mohammed Elsafy Received: 16 September 2023 / Accepted: 13 January 2024 © The Author(s) 2024 Abstract Given the dioecious nature of date palms, selecting an effective pollinizer bearing a substantial quantity of high-quality pollen is imperative. In this study, we investigated the effects of 11 male date palm cultivars from Tunisia on the production of female trees, fruit sets, and the characteristics of ’Deglet Nour’ cultivar dates. The comparison of pollen germination rates showed that ABD1 and P169 pollens exhibited outstanding viability, with 98.7% and 98.3%, respectively. On the other hand, P169 pollen had the highest germination rate, at 86.3%. The most remarkable fruit set (90.7%) and retention rate (69.7%) were observed in response to P13 pollen. In response to the P165 pollinator, the fruit stood out among the resulting fruits for their notable weight, averaging 11.6 g. In addition, pollination with P90 increased total soluble solids (measured at 74.4°Brix in the Tamr stage), whereas P7-pollinated fruits recorded the highest levels of reducing sugars, reaching 41%. Notably, the highest acidity levels were found in P7-pollinated fruits (0.29%), and pollen K. Kadri · M. Jemni · S. Makhlouf Regional Research Center on Oasis Agriculture of Degache, BP 62, km1 Road of Tozeur, 2260 Degache, Tunisia e-mail: S. S. Sharma TERI‑Deakin Nano‑Biotechnology Centre, The Energy and Resources Institute, Gurugram, Haryana 122 001, India e-mail: M. Jemni e-mail: S. Makhlouf e-mail: K. Kadri Laboratory of Biotechnology Applied on Agriculture, National Institute of Agronomic Research of Tunis, University of Carthage, Street Hedi Karray, 2049 Ariana, Tunisia A. A. Malik Department of Biotechnology, TERI School of Advanced Studies, Vasant Kunj, New Delhi, India e-mail: M. Elsafy (*) Department of Plant Breeding, Swedish University of Agricultural Sciences, Alnarp, Skåne, Sweden e-mail: M. Mesnoua Department of Phœniciculture, Biotechnology, and Valorization of Date Palm Products and By‑Products, Centre for Scientific and Technical Research on Arid Regions, BP 1682 R.P., 07000 Biskra, Algeria e-mail: Vol.: (0123456789) 13 Genet Resour Crop Evol sources significantly influenced the fruits’ mineral content. Moreover, regarding pomological characteristics, fruits pollinated with P4 attained maximum size, measuring 4.10 cm. Conversely, P7-pollinated fruits had a notable width of 2.02 cm. These findings illustrate the possibility of the selective application of high-value pollinizers and emphasize the direct influence of pollen sources on fruit quantity and quality. Keywords Date palm · Pollen source · Fruit characteristics · Metazinia Introduction The date palm (Phoenix dactylifera L.) is a dioecious, perennial, diploid, monocotyledonous plant. Its dioecious reproduction has resulted in significant variability when propagated by seed (Alyafei et al. 2022; Mesnoua et al. 2020; Mesnoua et al. 2018a, b). The extensive genetic diversity of date palm has enabled the selection of numerous clones with differing morphological and physiological traits. Consequently, date-growing countries possess a rich genetic heritage, and two types of genetic resources can be distinguished: first, the millions of date palm hybrids obtained via seeds, and second, those derived from vegetative propagation. According to estimates, there are more than 500 recognized date palm cultivars in Iraq, 400 in Iran, 300 in Libya, 223 in Morocco, 940 in Algeria, and roughly 250 in Tunisia (Hannachi 1998; Rhouma et al. 2007) Thus, it is crucial to understand the genetic resources of cultivated species to increase productivity and efficiency in conservation and breeding efforts. Conversely, male pollinators are pivotal in the date production cycle due to the metaxenic impact of pollen on fruit-setting rates and yields, which underscores the significance of selecting and characterizing adequate male specimens (Karim et al. 2022a, b; Mesnoua et al. 2018a, b; Mesnoua et al. 2023). Furthermore, these male cultivars constitute exceptionally diverse gene pools, highlighting substantial biodiversity (Karim et al. 2022; Khouane et al. 2020). In contrast to Middle Eastern countries where male date palm cultivars have been thoroughly studied (Hannachi 1998; Hannachi et al. 1998; Rhouma et al. 2007), The genetic makeup of male date palms Vol:. (1234567890) 13 has not been extensively studied. Additionally, limited characterization research has been conducted in North African countries (Kadri et al. 2021; Karim et al. 2015; Khouane et al. 2020). In Tunisia, locally known as "Dokkars," these male trees are heterogeneous populations that are rarely cloned, with each individual exhibiting distinct traits (Bouguedoura et al. 2015). However, it is sometimes identified by the name of a phenotypically similar female cultivar. Selecting quality pollen sources with abundant pollen production is essential in date palm cultivation. In Tunisia, male date palm trees are poorly characterized and often seed propagated, unlike in other date-growing countries (e.g., Iraq) where superior males are cloned via vegetative means and have designated names ’Fahl’ such as ’Red Ganami,’ ’Green Ganani,’ and ’Gholami’ (Bouguedoura et al. 2015). Multiple investigations have shown that pollen sources influence fruit quality (Farag et al. 2012; Mohammadi et al. 2017; Rezazadeh et al. 2013; Soliman 2020). Pollen can also affect seed size and shape (xenia effect) and the tissue surrounding the embryo and endosperm (metaxenia effect). This study, therefore, sought to investigate the effects of eleven different pollen sources on the agronomic characteristics and chemical composition of the ’Deglet Nour’ date variety under the soil and climatic conditions of the Djerid region in southwestern Tunisia. Materials and methods Plant material, pollen collection, and pollination method This research was conducted on male date palm trees that were 30 years old. Eleven pollinizers from Tunisian germplasm were selected based on their blooming period and pollen germination rate (as shown in Tables 1 and 2). These pollinizers were grown in the regional oasis agriculture research center located in the district of Degache, governorate Tozeur, southwestern Tunisia (E: 33°58ʹ40.5ʺ; N: 008°12ʹ31.8ʺ). The palm trees were healthy, had uniform vegetative growth and pollen production, and received regular agricultural practices such as irrigation and fertilization. A single male tree was used for each pollen source, and the pollen was collected during the second flowering Genet Resour Crop Evo (...truncated)