Abstract
Date Palm (Phoenix dactylifera L.) is one of the oldest domesticated fruit trees. For future breeding program, knowledge on genetic structure of cultivars is necessary. Therefore, the present study was performed with the following aims: 1- To provide data on genetic diversity and genetic structure of 36 date palm cultivars, 2- To provide data on the association between fruit characteristics and the genetic features of the cultivars. We used nine SSRs and EST-SSR loci for our genetic investigation. The most of SSR loci obtained have a high Gst value (0.70), and therefore have a good discrimination power for date palm cultivar differentiation task. K-Means clustering grouped date palm cultivars either in two broad clusters, or in 16 smaller genetic groups. This was supported by delta K = 2 of the STRUCTURE analysis. AMOVA produced significant genetic difference among date palm cultivars (PhiPT = 0.70, P = 0.001). New genetic differentiation parameters estimated also produced significant difference among date palm cultivars (G’st (Nei) = 0.673, P = 0.001; G’st (Hed) = 0.738, P = 0.001). Test of assignment revealed that some of the cultivars have 33-66% misassignment, probably due to genetic admixture. Heatmaps of genetic versus morphological and agronomical characters in date palm cultivars differed from each other showing the cultivars morphological changes is not merely related to their genetic content. It points toward the potential role played either by environmental conditions or local selection practice. The new findings can be utilized in future conservation and breeding of date palms in the country.
Highlights
Plant species of the family Palmae/ or Arecaceae are distributed mainly in tropical and subtropical areas, but a few species grow at higher latitudes in the southern hemisphere
We used 36 cultivars including 122 trees were collected from Ahwaz germplasm collection (Omol-tomair station of Date Palm & Tropical Fruits Research Center, Ahwaz, Iran) and different date palm orchards located in Hormozgan and kerman provinces, Iran (Saboori et al 2019, Saboori et al 2020)
The suitability of SSR and EST-SSR bands for date palm population genetic studies was determined by DCA plot (Fig. 2)
Summary
Plant species of the family Palmae/ or Arecaceae are distributed mainly in tropical and subtropical areas, but a few species grow at higher latitudes in. Different molecular markers (neutral, multilocus and DNA-sequence based markers) have been utilized in date palm genetic diversity investigations as well as cultivar phylogeny analyses (see for example, Sharifi et al 2018, Saboori et al 2019, Saboori et al 2020). According to Brommer (2011) “divergence across populations of species that are less amenable for proper QST estimation may still be of considerable evolutionary or conservation interest’’ and it can be assessed by using PST This in turn estimates the quantitative genetic differentiation (i.e., additive genetic variance) using quantitative trait measurements within populations (Brommer, 2011). Phenotypic differentiation index (PST) is an estimate of quantitative genetic differentiation (i.e., additive genetic variance) using quantitative trait measurements within populations (e.g., plant size, growth rate, etc.; Brommer, 2011)
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