Phenotypic data from: from buds to shoots: insights into grapevine development from the Witch’s Broom bud sport

Background Bud sports occur spontaneously in plants when new growth
exhibits a distinct phenotype from the rest of the parent plant. The
Witch’s Broom bud sport occurs occasionally in various grapevine (Vitis
vinifera) varieties and displays a suite of developmental defects,
including dwarf features and reduced fertility. While it is highly
detrimental for grapevine growers, it also serves as a useful tool for
studying grapevine development. We used the Witch’s Broom bud sport in
grapevine to understand the developmental trajectories of the bud sports,
as well as the potential genetic basis. We analyzed the phenotypes of two
independent cases of the Witch’s Broom bud sport, in the Dakapo and Merlot
varieties of grapevine, alongside wild type counterparts. To do so, we
quantified various shoot traits, performed 3D X-ray Computed Tomography on
dormant buds, and landmarked leaves from the samples. We also performed
Illumina and Oxford Nanopore sequencing on the samples and called genetic
variants using these sequencing datasets. Results The Dakapo and Merlot
cases of Witch’s Broom displayed severe developmental defects, with no
fruit/clusters formed and dwarf vegetative features. However, the Dakapo
and Merlot cases of Witch’s Broom studied were also phenotypically
different from one another, with distinct differences in bud and leaf
development. We identified 968–974 unique genetic mutations in our two
Witch’s Broom cases that are potential causal variants of the bud sports.
Examining gene function and validating these genetic candidates through
PCR and Sanger-sequencing revealed one strong candidate mutation in Merlot
Witch’s Broom impacting the gene GSVIVG01008260001. Conclusions The
Witch’s Broom bud sports in both varieties studied had dwarf phenotypes,
but the two instances studied were also vastly different from one another
and likely have distinct genetic bases. Future work on Witch’s Broom bud
sports in grapevine could provide more insight into development and the
genetic pathways involved in grapevine.