Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.64898/2026.09.24.754277

The bacterial pathogen causing cucurbit yellow vine disease associates with the specialized extrafascicular phloem unique to cucurbits

Mphande, K.·LaSarre, B.·Gleason, M. L.·Beattie, G. A.
View original source ↗Export metadata ↓

Abstract

Cucurbit yellow vine disease (CYVD) is a phloem disease caused by a group of Serratia ureilytica bacteria within the S. marcescens complex. The CYVD pathogen is distinct from other phloem pathogens in two fundamental ways: i) unlike other bacterial phloem pathogens, the CYVD pathogen readily grows on standard laboratory media; and ii) whereas most bacterial phloem diseases are transmitted solely by hemipteran insects, CYVD can be transmitted by both hemipteran (squash bug) and non-hemipteran (cucumber beetle) vectors. The phloem of cucurbits is also distinct, with cucurbits having a unique secondary phloem system, the extrafascicular phloem (EFP), for which a role in CYVD has not been investigated. The distinctive features of this pathosystem prompted a re-evaluation of pathogen localization in planta using a green fluorescent protein-tagged CYVD strain during infection of squash (Cucurbita pepo). In epifluorescence and confocal microscopy images of transverse and longitudinal sections of stem and petiole tissues, the fluorescence patterns of the CYVD pathogen were consistent with pathogen colonization of all four known EFP tissues, namely the peripheral, entocyclic, ectocyclic, and commissural sieve tubes. The CYVD pathogen may enter the EFP during herbivory by pathogen-infected vectors that cause mechanical damage, as the EFP exhibits much slower blockage following injury than the conventional fascicular (bundle) phloem. Moreover, although EFP has been proposed to have an antimicrobial function, EFP exudate collected from the stem and petioles of C. pepo supported rapid pathogen growth. These results provide evidence for a unique tissue tropism of the newly emerged plant pathogen S. ureilytica.

Explore related subjects

plant biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Mphande, K., LaSarre, B., Gleason, M. L., Beattie, G. A.. 2026-09-28. The bacterial pathogen causing cucurbit yellow vine disease associates with the specialized extrafascicular phloem unique to cucurbits. https://doi.org/10.64898/2026.09.24.754277

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Seeding paradise: germination ecophysiology of Xyris paradisiaca Wand. (Xyridaceae), an endangered endemic species from Central Brazil

Seed ecophysiology is essential for understanding plant regeneration and developing effective conservation and ecological restoration strategies, yet knowledge remains scarce for most threatened Cerrado species. We characterised the germination niche, desiccation tolerance and storage behaviour of Xyris paradisiaca (Xyridaceae), an Endangered species endemic to Central Brazil, to assess whether its restricted distribution is associated with narrow germination requirements and to inform seed-based conservation. Germination was tested across light regimes, constant temperatures, decreasing water potentials and short-duration heat shocks, while thermal- and hydro-time models were used to quantify thermal and hydric thresholds. Seeds exhibited an absolute light requirement but broad abiotic tolerances. Germination remained >87% between 15 and 40 {degrees}C, with estimated cardinal temperatures of Tb = 8.94 {degrees}C, To = 33.13 {degrees}C and Tc = 45.53 {degrees}C. Germination remained similar to the control down to -0.6 MPa and exceeded 40% at -1.0 MPa, with a median base water potential of {Psi}b = -1.03 MPa. Germination also remained high after 1-min heat shocks up to 200 {degrees}C. Seeds were desiccation tolerant, with 100% germination after drying and a viability loss index of -0.04, and germination remained >90% after 24 months of ambient storage. Thus, the highly restricted distribution of X. paradisiaca is not driven by a narrow physiological germination niche. Its broad environmental tolerances, desiccation tolerance and favourable storage behaviour also highlight its unexplored potential for seed-based restoration, propagation and ex situ conservation.

plant biology↗
bioRxiv2026

Planted origin of shade trees: a robust determinant of cocoa yield among smallholder farmers in Cote d'Ivoire

CONTEXT: While the agroeconomic literature on the determinants of cocoa yield among West African smallholders is abundant, it remains dominated by descriptive studies or work conducted at an aggregated regional scale, leaving open the question of the role of shade-tree management practices at the scale of the individual plantation. OBJECTIVE: This study tests whether shade-tree management practices and the farmer's socio-demographic profile explain variation in cocoa yield, using a nationwide sample of 409 plantations covering, for the first time, the three major Ivorian production zones (loops) (98, 151 and 160 plantations for loops 1, 2 and 3, respectively). METHODS: A univariate screening of 27 variables, a mixed model with a random intercept by village, a production-function specification, LASSO variable selection, and a random forest were applied, all evaluated by 5-fold cross-validation. RESULTS AND CONCLUSIONS: The five approaches converge on a robust result: the deliberately planted origin of shade trees (as opposed to a residual or spontaneous origin) is the strongest and most stable determinant of yield, with a mean gap of 332 versus 183 kg/ha/year. This effect withstands four successive robustness checks: it remains significant after simultaneous adjustment for age, plantation size, production zone, technical extension, and farmer education; it is not driven by a handful of extreme plantations; it holds within each of the three production zones taken separately rather than in only one of them; and, taken in isolation, it retains a positive out-of-sample predictive power (cross-validated R2=8776; 0.05). A second group of robust determinants of more modest magnitude emerges for agricultural technical extension (ANADER/CNRA/SATMACI) and farmer education level; shade-tree alignment shows a signal in the same direction, consistent with recent independent work in Cote d'Ivoire, but becomes statistically marginal once adjusted for these other factors. The full multivariate model reaches a cross-validated R2 of around 0.07-0.08. SIGNIFICANCE: This signal, undetectable in an analysis restricted to loop 1 alone (n=98) for lack of statistical power, confirms the value of nationwide sampling for detecting modest but real agronomic determinants, and argues for integrating shade-tree origin into agroforestry extension programmes.

plant biology↗
bioRxiv2026

Parental Genome Assemblies of Suyunuo1 Reveal Structural Variation Underlying Edible Waxy Maize Evolution, Superior Hybrid Performance and Yield - Flavor Balance

Edible waxy maize is a unique domesticated cereal valued for its superior sensory and nutritional properties, yet high quality gap free genomes remain lacking, hindering the exploration of structural variations (SVs) and domestication related divergence. Here, we assembled two chromosome level, gap free genomes of the elite waxy maize inbred lines Tongxi 5 and Hengbai 522, the parents of the widely cultivated hybrid Suyunuo 1. Comparative genomic analysis revealed substantial genome size variation, prominent megabase scale SVs, and extensive knob repeat expansion in Tongxi 5. We identified widespread gene presence absence variation and hyperdivergent regions enriched in transposable elements, which largely underpin genomic differentiation between waxy and field maize. Population genomic analyses further demonstrated asymmetric introgression from field maize into the two parents, whereas the conserved waxy haplotype supports a shared ancestral origin. Integrative GWAS based on SNPs, InDels and SVs revealed that SVs substantially contribute to phenotypic diversity and mediate the co-regulation of yield traits and flavor-related metabolites. Our results uncover key genomic events underlying post-domestication divergence and highlight the essential roles of SVs in heterosis and flavor-yield balance, providing valuable genomic resources for waxy maize improvement.

plant biology↗