The Pollen Viability and Characteristics Difference Analysis Between the Domesticated Species and Other Species in Juglandaceae

This study provides a comparative analysis of pollen morphology and viability in seven representative species of the Juglans, Carya, and Pterocarya genera of the Juglandaceae family to inform hybridization breeding programs. Pollen morphology was observed using scanning electron microscopy (SEM). MTT staining was used to determine the decay of pollen viability under 4°C cold storage conditions. Combined with pollen tube length measurement, the study characterizes interspecific differentiation in these traits and discusses the observed patterns in relation to species’ domestication status. The results showed significant differences in pollen morphology among species: Carya illinoinensis pollen was the largest, while Pterocarya stenoptera pollen was the smallest. Juglans species had a larger number of germinal apertures, while Carya and Pterocarya species had fewer. Furthermore, the distribution of germinal apertures differed between genera. Interspecific variation was observed in pollen tube length, with Juglans regia showing the longest pollen tubes, whereas no significant differences were detected among P. stenoptera, Carya cathayensis and Juglans nigra. In terms of pollen viability, domesticated species, such as J. regia and C. illinoinensis, exhibited higher initial viability than wild species, but subsequently declined more rapidly. The extremely high sterility rate (0.16 ± 0.05%) of pollen from J. hopeiensis is consistent with the hypothesis of its hybrid origin. Pollen size and pollen tube length showed patterns associated with viability decline, potentially suggesting a trade-off between initial reproductive efficiency and long-term preservation capacity. Further investigation is needed to determine if these patterns are linked to domestication history. This study provides empirical data on interspecific pollen differences, offering a foundational reference for hybrid breeding in Juglandaceae.