Phenotypic and Inter-Annual Variability of Mulberry (Morus Spp.) Fruit Quality in an Ex-Situ Collection

This paper reports a two-year (2025-2026) phenotypic characterization of an ex-situ mulberry (Morus spp.) germplasm collection at the Research Station for Fruit Growing Băneasa – Moara Domnească experimental base, Romania, comprising two complementary components. First, 17 accessions (one tree per accession, 20 fruits per tree) were evaluated in 2026 for fruit weight, height and diameter; one-way ANOVA indicated significant differences among the sampled accessions for all three traits, with Duncan's multiple range test separating several homogeneous subsets. Second, six of these accessions, sampledidentically in 2025 and 2026, were compared between years for fruit weight, height, diameter, soluble solids (Brix) and pH. Fruit weight, height and diameter were significantly higher in 2026 than in 2025 (paired t-tests, p < 0.05), and mean Brix was also higher in 2026, although this was not consistent across all six accessions; pH did not differ significantly between years.These inter-annual differences coincided with a lower vapour pressure deficit (VPD) during the fruit-development window in 2026 than in 2025, together with markedly higher rainfall in the same period. Because the trial spanned only two growing seasons, this climatic association is presented as an interpretive hypothesis rather than a statistically tested causeeffect relationship. As each accession in the 2026 characterisation is represented by a single tree, the observed differences describe variability among the sampled accessions rather than a fully replicated test of genotypic effect