DATE PALM DIVERSITY IN PAKISTAN AND ITS RELATIONSHIP WITH WORLD DATES GERMPLASM FOR EXPLORING THE CENTER OF ORIGIN OF PHOENIX DACTYLIFERA (L.)

Abstract

Date Palm, (Phoenix dactylifera L.) often called ‘nakhl’, ‘khajor’, or ‘khaji’ belonging to the family Arcaceae (Dransfield et al., 2008) is an evergreen tree. It is the hardiest among tropical fruit trees and exceeds most other fruit crops in productivity and adaptability. The characterization of date palm at the genetic level supplemented with phenotypic character is of great concern as an important step towards efficient conservation, maintenance and utilization of the existing genetic diversity. The present research work was carried out to investigate the phenotypic variability and genetic diversity of the date palm germplasm present in the 16 districts of Pakistan. A planned survey of date palm growing regions of Pakistan in 4 provinces (Punjab, Sindh, Khyber Pakhtunkhwa and Balochistan) and Azad Jammu and Kashmir was conducted for collecting leaf and fruit samples of date palm. Young and healthy leaves were used to extract DNA whereas seeds were extracted from fruit for recording qualitative and quantitative morphometric diversity. In total, 2460 seeds of 82 accessions were included in morphometric study. About 139 date palm accessions were evaluated for genetic variability and population structure. The recorded data were analyzed using a set of different statistical tools for making significant interpretation. A total of 19 traits (5 quantitative and 14 qualitative) enabled an assessment of phenotypic diversity and structure. The measured traits: dorsal area, lateral area, embryo to apex length, embryo to base length and their percentage, seed base, micropyle position, seed wings and frequency of wings were more variable. PCA grouped all the accessions according to their phenotypic relations and morphometric characteristics. Cluster analysis distributed all the 82 Pakistani date palm accessions into their three original groups. The results reflect huge seed morphometric variation and presented seeds as a powerful tool for phenotyping. Furthermore, our study also exhibited strong resemblance and possible relationship between some groups of accessions. All 18 SSR primer pairs successfully analyzed molecular genetic variation and produced multiple fragments in the Pakistani collection as well as in date palm germplasm representing 10 different date palm growing regions of the eastern and western world. These set of markers proved themselves as highly polymorphic for genetic diversity estimation and population structure within and among all the geographically spaced population of xvii worldwide accessions. The findings of implemented markers revealed 2-23 alleles per locus with high level of expected heterozygosity in the accessions collected from Pakistan. The most informative SSR marker in this study was mPdCIT078. In addition, cultivar identification key were established. It allowed resolving the difference and constructs the relationships of the same name or vice versa. Our results also suggested the existence of population subdivision at the regional level. Population from semi arid – monsoonal or canal irrigated (seasonal or perennial) belt of Punjab (Bhakkar, Muzafargarh and Rahim Yar Khan) and dry arid ecological zones of Balochistan (Kech, Gwadar) are stable in their structure whereas DAPC distributed 342 accessions of 10 date palm growing countries into two major geographical groups (eastern and western). It is concluded that Pakistani germplasm has huge diversity and genetic pool were close to the eastern world especially Iraq and Oman.