GENETIC STUDIES ON DATE PALM (Phoenix dactylifera L.) GERMPLASM GENE POOLS FROM JIGAWA, NIGERIA

Abstract

Date palm is cultivated in arid and semiarid regions worldwide. In Nigeria, date palm is one of the most important tree crops of great socioeconomic importance in the Sahel, Sudan and Guinea Savannah ecologies. In order to assess the genetic diversity of the crop, survey and exploration were undertaken to collect the fruits from the populations of the female tree germplasm across the gene pools of the Nigerian Institute for Oil Palm Research (NIFOR), date palm research substation located in Dutse, Jigawa state, Nigeria. A total of 21 accessions were randomly collected across the gene pools. The fruits collected were analysed for their proximate and phytochemical compositions. The accessions were also evaluated for morphological characteristics using completely randomised block design (CRBD), Quantitative and qualitative characters were taken for the fruits following standard procedures. Random amplified polymorphic DNA (RAPD) technique was used to determine genetic diversity and sex identification. The cytological analysis was carried out using standard procedures. Results of the proximate composition showed that the accession R13P5 had the highest moisture content of 7.65 %. The highest carbohydrate content was observed in R4P12 with 82.32 %. The result of the mineral analysis showed that R24P9 had the highest calcium, magnesium, sodium and potassium with 119.39, 80.55, 13.44 and 423 mg/100 g respectively. The sugar content analysis showed that R5P8 had the highest glucose (320 mg/g) content while R15P6 recorded highest in fructose and sucrose (102 and 92 mg/g) content respectively. At late seedling stage, the highest plant height and girth size were observed in accessions R13P5 (39.00 cm) and R5P8 (10.00 cm). The results of the fruit characteristics showed that R7P1 had the highest fruit weight, fruit diameter and fruit thickness of 11.85 g, 2.10 mm, and 4.00 mm, respectively. The molecular diversity results revealed a total of 125 amplified fragments with 6 primers, of which 106 (84.3 %) were polymorphic and 19 (15.2 %) were monomorphic. Out of the total of 21 accessions screened for sex determination, 12 accessions (R13P1, R4P12, R5P8, R3P22, R1P18, R7P1, R13P5, R13P9, R14P21, R4P29, R16P31 and zariya showed male pattern and 9 accessions (R24P9, R5P20, R2P4, R9P2, R6P20, R9P21, R5P24, R5P6, R1P10) were observed to be female. The morphological variations in the male accessions revealed a larger girth size and higher number of lower leaf spines while the female accessions showed a smaller girth size with little to absence of lower leaf spines. Cytological examination of some of the accessions confirmed 2n=36 number of chromosomes in accessions (R5P8 and R16P31) and 2n = 28 chromosomes in accession R1P18 with metacentric and submetacentric chromosomes respectively. The high genetic variability observed among the date palm germplasm for proximate, morphological and molecular characterisation has provided baseline information among the date palm germplasm in the gene pools. The developed sex determinant qualitative marker could be used for gender identification at the seedling stage of date palms in order to save time. Plant breeders and growers may adopt this marker as a potential tool for gender identification in date palm seedlings before they are transplanted in the field.