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Societal Impact StatementThe innumerable effects of terroir—including climate, soil, microbial environment, biotic interactions, and cultivation practice—collectively alter plant performance and production. A more direct agricultural intervention is grafting, in which genetically distinct shoot and root genotypes are surgically combined to create a chimera that alters shoot performance at a distance. Selection of location and rootstock are intentional decisions in viticulture to positively alter production outcomes. Here, we show that terroir and rootstock alter the shapes of grapevine leaves in commercial vineyards throughout the California Central Valley, documenting the profound effects of these agricultural interventions that alter plant morphology. SummaryEmbedded in a single leaf shape are the latent signatures of genetic, developmental, and environmental effects. In viticulture, choice of location and rootstock are important decisions that affect the performance and production of the shoot. We hypothesize that these effects influence plant morphology, as reflected in leaf shape.We sample 1879 leaves arising from scion and rootstock combinations from commercial vineyards in the Central Valley of California. Our design tests 20 pairwise contrasts between Cabernet Sauvignon and Chardonnay scions from San Joaquin, Merced, and Madera counties from vines grafted to Teleki 5C, 1103 Paulsen, and Freedom rootstocks.We quantify clear differences between Cabernet Sauvignon and Chardonnay leaves. However, we also detect a separate, statistically independent source of shape variance that affects both Cabernet Sauvignon and Chardonnay leaves similarly. We find that this other shape difference is associated with differences in rootstock and location.The shape difference that arises from rootstock and location affects the basal part of the leaf near the petiole, known as the petiolar sinus, and affects its closure. This shape effect is independent from previously described shape differences that arise from genetic, developmental, or size effects. 

Abstract BackgroundBud 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. ResultsThe 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. ConclusionsThe 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. 

Grapevine leaves have diverse shapes and sizes which are influenced by many factors including genetics, vine phytosanitary status, environment, leaf and vine age, and node position on the shoot. To determine the relationship between grapevine leaf shape or size and leaf canopy temperature, we examined five seedling populations grown in a vineyard in California, USA. The populations had one parent with compound leaves of the Vitis piasezkii type and a different second parent with non-compound leaves. In previous work, we had measured the shape and size of the leaves collected from these populations using 21 homologous landmarks. Here, we paired these morphological data with canopy temperature measurements made using a handheld infrared thermometer. After recording time of sampling and canopy temperature, we used a linear model between time of sampling and canopy temperature to estimate temperature residuals. Based on these residuals, we determined if the canopy temperature of each vine was cooler or warmer than expected, based on the time of sampling. We established a relationship between leaf size and canopy temperature: vines with larger leaves were cooler than expected. By contrast, leaf shape was not strongly correlated with variation in canopy temperature. Ultimately, these findings indicate that vines with larger leaves may contribute to the reduction of overall canopy temperature; however, further work is needed to determine whether this is due to variation in leaf size, differences in the openness of the canopy or other related traits.