Hybridization and Metaxenial Effects on Biochemical Attributes and Hybrid Development in Date Palm (Phoenix dactylifera L.) Hillawi. Cultivar

Abstract

: Date palm (2n = 36) is a monocotyledonous, dioecious plant, which belongs to the family Arecaceae . Pollens are the primary source of diversity and improvement in quality, yield, ripening time, and size. Therefore, in this study, we investigated the differential behavior of nine pollen sources, collected from different locations, upon pollination with date palm female cultivar Hillawi. Metaxenia effect of pollen grains on the maternal tissues of fruits was carried out at khalal stage, whereas the seeds obtained from these fruits were planted in a nursery for hybrid confirmation. Biochemical characteristics; proximate analysis; individual sugar (sucrose, glucose, and fructose), total sugar, ascorbic acid, total soluble solid, and total phenolic contents; and 2,2-diphenyl-l-picrylhydrazyl (DPPH) and enzymatic activities (catalase, peroxidase, protease, and superoxide dismutase) were significantly variable. Dendrogram for biochemical parameters of cultivar Hillawi, created using Ward’s method, revealed three clusters. Among the nine pollen sources, M8 was superior because it was positively associated with most of the variables. M7 shortened the ripening time, and its progeny exhibited the highest ascorbic acid content. Fruits developed from M8 pollination exhibited higher total sugar contents, protein, antioxidant and enzymatic activity, and had shortened ripening time. For more positive correlation of pollen parents, M8 was followed by M7, M3, M5, and M4. Strong positive correlation was found among most of the traits. Biochemical analyses revealed that these traits were suitable for metaxenia studies and breeding programs, as they exhibited quality and yield enhancement. The seedlings developed from these seeds, which were a result of controlled pollination, were identified as true date palm hybrids using 12 simple sequence repeats (SSRs) markers. Out of 12, only six primers clearly differentiated between true and ambiguous hybrids. Primer mpdCIR-10 identified the highest number of true hybrids 13 (81.25%). These findings will be useful for future studies.