Genetic Diversity on Farm in Japanese Paper Mulberry

Area of Science:

• Plant genomics
• Molecular biology
• Botany

Background:

• Paper mulberry (Broussonetia x kazinoki) is crucial for traditional Japanese Washi paper.
• Elite strains are vegetatively propagated, but their genetic diversity and origins require further investigation.

Purpose of the Study:

• To reconstruct and compare complete chloroplast genomes of Japanese paper mulberry strains.
• To identify genetic polymorphisms and elucidate the maternal lineages and origins of B. x kazinoki.

Main Methods:

• Reconstruction of complete chloroplast (cp) genomes for three elite strains.
• Identification of insertion/deletion (INDEL) polymorphisms by comparing cp genomes.
• Application of Inter Simple Sequence Repeat (ISSR)-based MIG-seq and Next-Generation Sequencing (NGS)-oriented nuclear markers.
• Principal Component Analysis (PCA) for discriminating regional groups.

Main Results:

• Three complete cp genomes were reconstructed (160,861–160,878 bp).
• Twenty-five INDEL polymorphisms were identified across the analyzed cp genomes.
• PCA distinguished two major groups, indicating distinct origins despite morphological similarities.
• Maternal markers revealed diverse origins of Japanese paper mulberry, and nuclear markers highlighted its heterogeneous nature.

Conclusions:

• Chloroplast genome analysis effectively identifies INDEL polymorphisms in paper mulberry.
• Genetic markers reveal complex and diverse origins of domesticated Japanese B. x kazinoki.
• Understanding genetic diversity is vital for the conservation and sustainable use of paper mulberry resources.