Natural variation in the control of flowering and shoot architecture in diploid Fragaria species

In perennial fruit and berry crops of the Rosaceae family, flower initiation occurs in late summer or autumn after downregulation of a strong repressor TERMINAL FLOWER1 (TFL1) and flowering and fruiting takes place the following growing season. Rosaceous fruit trees typically form two types of axillary shoots, short flower-bearing shoots called spurs and long shoots that are respectively analogous to branch crowns and stolons in strawberry. However, regulation of flowering and shoot architecture differs between species and environmental and endogenous controlling mechanisms have just started to emerge. In woodland strawberry (Fragaria vesca L.), long days maintain vegetative meristems and promote stolon formation by activating TFL1 and GIBBERELLIN 20-OXIDASE4 (GA20ox4), respectively, while silencing of these factors by short days and cool temperatures induces flowering and branch crown formation. We characterized flowering responses of 14 accessions of seven diploid Fragaria species native to diverse habitats in the northern hemisphere, and selected two species with contrasting environmental responses, F. bucharica Losinsk. and F. nilgerrensis Schlecht. ex J. Gay for detailed studies together with F. vesca. Similar to F. vesca, F. bucharica was induced to flower in short days at 18°C and regardless of photoperiod at 11°C after silencing of TFL1. F. nilgerrensis maintained higher TFL1 expression level and likely required cooler temperatures or longer exposure to inductive treatments to flower. We also found that high expression of GA20ox4 was associated with stolon formation in all three species, and its downregulation by short days and cool temperature caused branch crown formation in F. vesca and F. nilgerrensis, although the latter did not flower. F. bucharica, in contrast, rarely formed branch crowns, regardless of flowering or GA20ox4 expression level. Our findings highlighted diploid Fragaria species as a rich source of genetic variation controlling flowering and plant architecture, with potential applications in breeding of Rosaceous crops.

Crown formation from a cavitating bubble close to a free surface

A rapidly growing bubble close to a free surface induces jetting: a central jet protruding outwards and a crown surrounding it at later stages. While the formation mechanism of the central jet is known and documented, that of the crown remains unsettled. We perform axisymmetric simulations of the problem using the free software program BASILISK, where a finite-volume compressible solver has been implemented, which uses a geometric volume-of-fluid (VoF) method for the tracking of the interface. We show that the mechanism of crown formation is a combination of a pressure distortion over the curved interface, inducing flow focusing, and of a flow reversal, caused by the second expansion of the toroidal bubble that drives the crown. The work culminates in a parametric study with the Weber number, the Reynolds number, the pressure ratio and the dimensionless bubble distance to the free surface as control parameters. Their effects on both the central jet and the crown are explored. For high Weber numbers, we observe the formation of weaker ‘secondary crowns’, highly correlated with the third oscillation cycle of the bubble.

A geochemical study of the Crown Formation and Bird Member lavas of the Mesoarchaean Witwatersrand Supergroup, South Africa

The ca. 2.97 to 2.80 Ga Witwatersrand Supergroup, South Africa, represents the oldest intracontinental sedimentary basin of the Kaapvaal craton. Two volcanic units occur in this supergroup: the widespread Crown Formation lavas in the marine shale-dominated West Rand Group and the more geographically restricted Bird Member lavas, intercalated with fluvial to fluvio-deltaic sandstone and conglomerate of the Central Rand Group. These units remain poorly studied as they are rarely exposed and generally deeply weathered when cropping out. We report whole-rock major and trace elements, Hf and Nd-isotope whole-rock analyses of the lavas from core samples drilled in the south of the Witwatersrand basin and underground samples from the Evander Goldfield in the northeast. In the studied areas, both the Crown Formation and Bird Member are composed of two units of lava separated by sandstone. Whereas all the Crown Formation samples show a similar geochemical composition, the upper and lower volcanic units of the Bird Member present clear differences. However, the primitive mantle-normalized incompatible trace element concentrations of all Crown Formation and Bird Member samples show variously enriched patterns and marked negative Nb and Ta anomalies relative to Th and La. Despite the convergent geodynamic setting of the Witwatersrand Supergroup suggested by the literature, the Crown Formation and Bird Member are probably not related to subduction-related magmatism but more to decompression melting. Overall, the combined trace element and Sm-Nd isotopic data indicate melts from slightly to moderately depleted sources that were variably contaminated with crustal material. Greater contamination, followed by differentiation in different magma chambers, can explain the difference between the two signatures of the Bird Member. Finally, despite previous proposals for stratigraphically correlating the Witwatersrand Supergroup to the Mozaan Group of the Pongola Supergroup, their volcanic units are overall geochemically distinct.

Evaluation of varieties (Citrus limon L.) according to economic and biological characteristics

Evaluation of seven introduced genotypes of lemon (CITRUS LIMON L.) of domestic and foreign selection in the Central Forest-Steppe of Ukraine (Department of Horticulture of Uman NUS) was carried out on the basis of economic and biological characteristics. Their systematic origin was determined and the possibility of using introduced varieties of Citrus Limon L. in the garden and park economy of the Central Forest-Steppe of Ukraine was investigated. The possibility of using introduced representatives of Citrus Limon L is highlighted and studied. in the horticultural economy of the central forest-steppe of Ukraine. Geographical origin has been clarified. The evaluation was carried out on decorative properties and basic economic and biological characteristics. Indicators of rhizogenesis of the studied varieties are carried out and generalized. This year, studies will be conducted on the phenological phases of development, flowering and fruiting of introduced plants, both in general and on the example of individual samples. A brief economic, biological and decorative characteristic of collectible lemon varieties in the conditions of the central forest-steppe of Ukraine is given, which are included in further research on the cultivation and reproduction of promising varieties for further use in gardening. For rooting, cuttings of 10–12cm in size were taken. leaving one pair of leaves on it. Rooting of Lemons was carried out on April 20–25, 2020 at an average daily temperature of 18°C. The soil mixture for rooting consisted of leaf humus, turf soil and sand in a ratio of 2: 1: 1. During rooting in the room where the experiment was conducted, optimal conditions for cuttings were provided, namely: maintaining the air temperature not lower than 25°C and humidity 80–85 %. Digging of rooted cuttings was carried out on September 24-45, 2020. After digging, an analysis of lemon rooting was performed. As a result of the conducted researches the received varietal samples had good development of root system and growth of shoots. During rooting, the cuttings were treated with a gel root-forming agent "Clonex". Plants of the selected varieties will be planted in mid-April, when the average daily air temperature will be 10–12°C so that the plants take root and do not die. In summer, it is planned to monitor the timing and frequency of flowering, the intensity of growth of young shoots, and crown formation.

Lhx6 regulates canonical Wnt signaling to control the fate of mesenchymal progenitor cells during mouse molar root patterning

Mammalian tooth crown formation has long served as a model for investigating how patterning and morphogenesis are orchestrated during development. However, the mechanism underlying root patterning and morphogenesis remains poorly understood. In this study, we find that Lhx6 labels a subpopulation of root progenitor cells in the apical dental mesenchyme, which is closely associated with furcation development. Loss of Lhx6 leads to furcation and root number defects, indicating that Lhx6 is a key root patterning regulator. Among the multiple cellular events regulated by Lhx6 is the odontoblast fate commitment of progenitor cells, which it controls in a cell-autonomous manner. Specifically, Lhx6 loss leads to elevated expression of the Wnt antagonist Sfrp2 and down-regulation of Wnt signaling in the furcation region, while overactivation of Wnt signaling in Lhx6+ progenitor cells partially restore the furcation defects in Lhx6-/- mice. Collectively, our findings have important implications for understanding organ morphogenesis and future strategies for tooth root regeneration.

Scientific achievements and realities of the sweet cherry (Cerasus avium L.) cultivation intensification at the current stage of the horticultural science development

The authors present the results of the comprehensive analysis of the influence of the modern horticultural science achievements on the sweet cherry cultivation intensification. Today in the world’s horticulture practice the main direction of increasing this crop plantations productivity is its comprehensive intensification. Its main link is the type of an orchard, and components – cultivar, rootstock, planting plan and the crown formation methods. In this relation, the major elements of the modern sweet cherry industrial cultivation technologies concerning these components were developed the place of the new inland developments being determined. The analysis of the approaches to the modern intense sweet cherry plantations creation has shown that they do not always correspond to this crop biological characteristics and sometimes are usual adoptions from the similar developments for apple. At the same time the development of the basic elements of the sweet cherry rootstocks and cvs growing intensification lag behing the requirements significantly and cannot be used in apple super-dense orchards. The Institute of Horticulture of the National Academy of Agrarian Sciences (NAAS) of Ukraine for the first time recommended for the Lisosteppe in of Ukraine three new types of orchards on vigorous, medium-sized and semi-dwarf rootstocks with the tree density placement from 417 to 1250 trees/ha in order to ensure the efficient industrial production of sweet cherries in particular, for the export purposes. These orchards are based mainly on using inland high-productive cvs, rootstocks and crown formation methods. The density of the trees placement in such orchards has been optimized by applying the mathematical modeling and tested in long-term field experiments. That enables to utilize effectively these orchards productivity potential. Their advantage as compared to foreign ones is that these plantations construction takes into account both the rootstocks vigour and the variety biological peculiarities. That is the basis for their application in the technologies for growing valuable sweet cherry cultivars which possess the increased consumers demand. The intensification of the sweet cherry growing should be based mostly on the creation of optimally dense plantations that meet the biological peculiarities of a concrete rootstock-cultivar combination

PHOTOSYNTHETIC PRODUCTIVITY OF CHERRY AND SWEET CHERRY LEAVES DUE TO ROOTSTOCK AND ARTIFICIAL FORMS OF TREE CROWNS IN THE GARDEN

In the scientific article presents the results of research on the study of varietal cherries and artificial ways of formation of the trees to the level of photosynthetic activity of leaves with the orientation of growing trees, their intensive technology. In the research, the varieties of cherries Shubinka, Podbelskaya and Shpanka Chernaya (black) zoned in the Republic, as well as sweet cherries Volovye serdtce, Revershon and Bahor, grown on a low-growing vegetatively propagated rootstock VVA-1 and VSL-2 (Krymsky-5) were used as the object of research. As a result of the conducted research, it was found that the optimal crown system for cherry and sweet cherry varieties is the five-skeletal wall. Crown formation in these forms helps to reduce the volume of the crown to an average of 25%, at which the net productivity of leaf photosynthesis in comparison with the usual crown formation – free-growing and sparse-tiered reaches a value of 34.73 grams/m2 per day. When forming bushy forms of the crown of cherries and sweet cherries, the level of leafiness of leaves improves and the content of chlorophyll in them increases to 13.42 mg/g of raw leaf mass. KEYWORDS: cherry, sweet cherry, density, variety, leaf, area, crown, forming, photosynthesis, productivity, pruning, index, projection.