Microstructure of Croatian Wild Grapevine (Vitis vinifera subsp. sylvestris Gmel Hegi) Pollen Grains Revealed by Scanning Electron Microscopy

X-ray Microanalysis of Elemental Composition of Vitis sylvestris Pollen Grains

The flowering and fruit set of grapevines are determined by many morphological, physiological, and environmental factors. Although the elemental composition of pollen grains plays a crucial role in the fruit set, there is still a considerable gap in our knowledge. To date, no study has been conducted on the elemental composition of Vitis vinifera subsp. sylvestris (hereafter V. sylvestris) pollen grains. The aim of this work was to investigate the elemental composition of pollen grains of V. sylvestris using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The pollen grains of ten V. sylvestris individuals (eight male and two female) and one hermaphrodite cultivar 'Plavac mali crni' were analyzed. SEM-EDX analysis revealed the presence of eight elements (carbon-C, oxygen-O, magnesium-Mg, phosphorus-P, potassium-K, calcium-Ca, molybdenum-Mo, and aluminum-Al) in the pollen grains. Interestingly, aluminum was detected exclusively in the pollen of the cultivated grape cultivar 'Plavac mali crni', while it was not present in the genotypes of V. sylvestris. No significant differences between genotypes were found for oxygen and phosphorus, while significant differences were found for other elements. Pollen dimorphism was not associated with differences in element composition, although principal component analysis separated the genotypes into two distinct groups, with two female individuals (Pak10 and Pak12) and one male (Im19) tending to form separate clusters. This study is the first report on the elemental composition of pollen grains of V. sylvestris genotypes and provides valuable insights for further studies on pollen functionality.

The wild side of grape genomics

With broad genetic diversity and as a source of key agronomic traits, wild grape species (Vitis spp.) are crucial to enhance viticulture's climatic resilience and sustainability. This review discusses how recent breakthroughs in the genome assembly and analysis of wild grape species have led to discoveries on grape evolution, from wild species' adaptation to environmental stress to grape domestication. We detail how diploid chromosome-scale genomes from wild Vitis spp. have enabled the identification of candidate disease-resistance and flower sex determination genes and the creation of the first Vitis graph-based pangenome. Finally, we explore how wild grape genomics can impact grape research and viticulture, including aspects such as data sharing, the development of functional genomics tools, and the acceleration of genetic improvement.

Revealing the intricate microcosm: Advancing invasive species pollen analysis through scanning microscopy of ultra sculpture

Micromorphological visualization of plant surface peculiarities provides valuable characters for the precise identification of plant species. Invasive alien species, introduced outside their native range, pose significant ecological, and health challenges. This study focuses on micromorphological investigations of selected invasive plant species belonging to the families Amaranthaceae, Asteraceae, Moraceae, Crassulaceae, Cannabaceae, Fabaceae, Commelinaceae, and Oxalidaceae. The study employs scanning electron microscopy (SEM) to analyze the species micromorphology of pollen structure in depth to characterize the sculpturing patterns. Additionally, the study examines the pollen characteristics of these invasive plants, including shape, size, and fertility, along with exine sculpturing. The maximum polar diameter was observed for Senna tora (41.2 μm). The spines in Achillea fragrantissima were measured to have dimensions of approximately 1.91 μm in length and 2.11 μm in width. The findings shed light on the allergy-causing potential of these invasive species, providing crucial information for accurate identification and effective management strategies to safeguard the indigenous flora of the region. The study contributes to the knowledge base for botanists, taxonomists, policy makers, climate experts, and biodiversity specialists. RESEARCH HIGHLIGHTS: Integrating SEM to analyze the pollen of invasive species. Unveiling pollen micromorphology of invasive species. Exploring the microscopic realm of invasive pollen to accurately identify the species.

Studies on pollen micro-morphology, pollen storage methods, and cross-compatibility among grape (Vitis spp.) genotypes

The knowledge of pollen morphology, suitable storage condition, and species compatibility is vital for a successful grapevine improvement programme. Ten grape genotypes from three different species, viz., Vitis vinifera L., Vitis parviflora Roxb., and Vitis champini Planc., were studied for their pollen structure and pollen storage with the objective of determining their utilization in grape rootstock improvement programs. Pollen morphology was examined through the use of a scanning electron microscope (SEM). The viability of the pollen was assessed using 2,3,5-triphenyltetrazolium chloride (TTC). In vitro pollen germination was investigated using the semi-solid medium with 10 % sucrose, 100 mg/L boric acid, and 300 mg/L calcium nitrate. The results revealed variations in pollen micro-morphology in 10 genotypes, with distinct pollen dimensions, shapes, and exine ornamentation. However, species-wise, no clear difference was found for these parameters. Pollen of V. parviflora Roxb. and Dogridge was acolporated and did not germinate. The remaining eight genotypes exhibited tricolporated pollen and showed satisfactory in vitro pollen germination. Storage temperature and duration interactions showed that, at room temperature, pollen of most of the grape genotypes can be stored for up to 1 day only with an acceptable pollen germination rate (>30 %). However, storage for up to 7 days was successfully achieved at 4 °C, except for 'Pearl of Csaba'. The most effective storage conditions were found to be at -20 °C and -196 °C (in liquid N2), enabling pollen storage for a period of up to 30 days, and can be used for pollination to overcome the challenge of asynchronous flowering. Four interspecific combinations were studied for their compatibility, among which V. parviflora Roxb. × V. vinifera L. (Pusa Navrang) and V. parviflora Roxb. × V. champini Planc. (Salt Creek) showed high cross-compatibility, offering their potential use for grape rootstock breeding. However, V. parviflora Roxb. × V. vinifera L. (Male Hybrid) recorded the lowest compatibility index among studied crosses. In the case of self-pollinated flowers from V. parviflora Roxb. and V. parviflora Roxb. × V. champini Planc. (Dogridge), pollen failed to germinate on the stigma due to male sterility caused by acolporated pollen. As a result, the flowers of these genotypes functioned as females, which means they are ideal female parents for grape breeding without the need for the tedious process of emasculation.

Pollen Morphology of Some Species from Genus Nitraria

An analysis of pollen grains (in Nitraria sibirica Pall., N. schoberi L., N. komarovii Iljin & Lava ex Bobrov, and N. pamirica L. Vassil.) was performed on natural material collected in Russia, Kazakhstan, and Tajikistan. Herbarium specimens from the collection at Komarov Botanical Institute, Russian Academy of Sciences (N. tangutorum Bobrov and N. praevisa Bobrov) were examined, too. Pollen grains of two species-N. pamirica and N. praevisa-were studied for the first time. N. tangutorum and N. praevisa were found to have the perprolate pollen shape, whereas N. pamirica was found to have the subprolate shape. An intraspecific differentiation of N. sibirica was noted. Populations of N. sibirica (Taskarasu, Karatal, and Basshi) possess pollen grains of the subprolate or prolate shape, striate and perforate exine ornamentation, and a longer equatorial axis and a shorter polar axis than other specimens of N. sibirica. N. schoberi in all populations had anomalous shapes of some pollen grains. Overall, we demonstrated that the length ratio of the polar axis to the equatorial axis, characteristics of pollen in polar view, colpus morphology, and surface ornamentation of pollen grains in the genus Nitraria are of great taxonomic importance for the identification of species.