Coconut genome size determined by flow cytometry: Tall versus Dwarf types

Area of Science:

• Plant genetics
• Genomics
• Molecular biology

Background:

• Coconuts (Cocos nucifera L.) exist as Tall and Dwarf types, with differing reproductive modes.
• A hypothesis suggests Dwarf coconuts may be variants of Tall types, potentially supported by genome size differences.
• Understanding genome size variation is crucial for coconut breeding and evolutionary studies.

Purpose of the Study:

• To estimate and compare the genome sizes of Tall and Dwarf coconut (Cocos nucifera L.) accessions.
• To investigate if genome size differences support the hypothesis of Dwarf coconuts originating from Tall variants.
• To characterize the overall genome size of Cocos nucifera L.

Main Methods:

• Flow cytometry was used to determine the 2C DNA content of 14 coconut accessions (eight Tall, six Dwarf).
• Leaf nuclei were stained with propidium iodide, with Pisum sativum as an internal standard.
• High-resolution histograms with low coefficients of variation were obtained for accurate measurements.

Main Results:

• Genome size (2C DNA content) ranged from 5.48 to 5.72 pg across all accessions.
• Mean genome sizes were 5.59 pg for Tall and 5.55 pg for Dwarf types.
• Small differences in genome size were observed between Tall and Dwarf coconut types.

Conclusions:

• The minimal genome size variation between Tall and Dwarf coconut types does not support the hypothesis that Dwarf types evolved from Tall types.
• The mean genome size of Cocos nucifera L. is classified as small (5.57 pg, 2723.73 Mbp/haploid set).
• Further research may be needed to explore other genetic mechanisms underlying coconut type differentiation.