Phenology and fruit set of peach trees cultivated in Dois Vizinhos, Paraná State, Brazil

Understanding the dormancy phases and dynamics of commercial cultivars in the regions where they are grown allows for the implementation of different cultural practices and aids in the understanding of the temperature requirements for collaboration with genetic improvement programs. The objective of this study was to determine the budding, flowering, and fruit set rates of peach trees cultivated in the municipality of Dois Vizinhos, Southwestern Paraná, Brazil. The present work was developed using the collection of peach trees in the fruit growing sector of the Universidade Tecnológica Federal do Paraná. Sixteen peach cultivars were evaluated: Rubimel, Leonense, Coral, Marli, Charme, Riograndense, Douradão, Chimarrita, Granada, BR-1, Bonão, and Eldorado (all planted in 2009), as well as Regalo, Kampai, Fascínio, and Zilli (planted in 2014). The experimental design was completely randomized with four replications of one plant each, in a 16 × 2 bifactorial arrangement (cultivars × year/harvest). Phenology evaluations were performed weekly by counting open (anthesis) and sprouted flower buds, and the fruit set rate was measured just before fruit thinning. Flowering (%), budding (%), and fruit set (%) rates were calculated. It was found that the year/harvest 2016 promoted the highest rates of sprouting and fruit set. The Bonão cultivar showed greater flowering intensity and regularity in the crop years evaluated (2016 and 2017). Coral and Kampai present fruit sets with greater intensities and regularities when compared to the other cultivars evaluated under the climatic condition of the municipality of Dois Vizinhos. The Riograndense cultivar showed greater irregularity in flowering and fruit production.

Application of ImageJ Software in the assessment of flowering Intensity and growth Vigor of pear Trees

The study evaluated the possibility of using the image acquisition and processing method with ImageJ software for estimating growth vigor and flowering intensity of ‘Conference’ pear trees. For assessing flowering intensity, manual counting of flower clusters and taking of photographs of the trees were conducted at full bloom. Tree vigor was estimated by manually measuring the total length of the central leader and shoots of individual trees. The trees were photographed from the same distance using a hand-held camera. The calibration model for assessing the vigor or flowering of trees by image analysis was based on measurements and photographs taken for nine selected trees differing in the total length of shoots or in the number of flower clusters. Then, a quality assessment of the model was carried out on 26 nonselected trees. Image processing was performed using ImageJ software. High regression coefficients were obtained between the surface area of petals measured on the photographs and the number of inflorescences counted (r2 = 0.98); however, observations carried out in the following year indicate the need for individual calibration of estimation models in each evaluation season. Subsequently, the quality of estimating the flowering intensity of pear trees was assessed using a previously determined calibration model. Mean absolute percentage error (MAPE) values ranged from 14.0% to 21.8%, depending on the measurement time. In the assessment of tree growth vigor, a high correlation (r2 = 0.98) was also obtained between the actual length of shoots measured individually for each tree and the values obtained by analyzing the photographic image, where the MAPE error was 12.9%.

Peculiarities in Scots pine (Pinus sylvestris L.) clones seeding on CSP (Cloning seed plantation) in western Polissya of Rivne region

The main purpose of seed orchards is to obtain regularly seeds of the highest genetic value for forest plantations. Long-term research in Ukraine and foreign experience show that there is a significant reduction in the cone yield on orchards that are over 26–28 years old even with free spacing of ramets. The aim of the study was to identify peculiarities in reproduction of Scots pine on Clonal Seed Orchards (CSO), based on comparison for performances of flowering intensity and seed production from different clones, their groups and CSO in Rivne region. The object of the study is the clonal seed orchards of Scots pine (Pinus sylvestris L.). The subject of research is the reproduction of clones on clonal seed orchards of Scots pine. The intensity of «flowering» and seeding of clones on CSO was determined by continuous list of each ramet. To assess the intensity of female «flowering», we determined the growth and the reproductive layer of the crown, the rank position of pine clones on plantations, which we divided into three groups: high, medium and weak. We analyzed the intensity of growth, «flowering» and seed production of Scots pine clones (Pinus silvestris L.) for many years on the plantations of 1977 and 1984. At CSP of 1977, the «flowering» within clones is characterized by a mixed-sexual type; on the plantation of 1984, the most clones (54.2%) were dominated by female «flowering». The rate of microstrobiles formation in clones on the younger plantation (CSP-1984) is lower than the intensity of megastrobiles formation by 4.0%, while on the older one (1977), on the contrary, the intensity of microstrobiles formation was dominant by 118.2%. The average yield of strobiles from the number of megastrobiles on the CSP of 1977 and 1984 was 70.1 and 74.3%, respectively. The close correlations were found between the number of megastrobiles and the number of strobiles (r = 0.94 and 0.84). The variation in the number of strobiles per tree over the years of observation is quite high and varied in clones of 1977 from 40.2% in 2004 to 70.7 in 2003 and averaged 52.6%; clones of 1984 ranged from 43.6% in 2004 to 78.8% in 2005 and averaged 59.3%. The number of female strobiles for the six-year period at CSP of 1977 averaged 45.8% from the number of male ones; for three years — 4.0% in clones of 1984. Their number ranged from 25.5 to 61.3% in clones of 1977; in clones of 1984 – from 16.5 to 77.5%. Depending on the clone and the weather conditions of the growing season, the ratio between the number of female and male strobiles within each clone is from 29.8 to 166.7% on CSP of 1977 and from 49.4 to 1005.4% of 1984. The correlation between the number of mega- and microstrobiles on CSP of 1977 is weak (r = 0.17), and the ones of 1984 – high (r = 0.77). No dependences were found between the preservation of megastrobiles by their number (abundance of «flowering») in clones of 1984 and the average correlation (r = 0.33) was found in clones of 1977. According to long-term data on CSP of 1977, the most productive is clone No 22. The highest yield of strobiles from the number of megastrobiles on the plantation of 1984 – in clone No 130 (88.1%), the lowest — No 121 (46.7%). Only two clones (No 22 and 97) and eight clones of 1984 (No 116, 118, 127, 129, 130, 137, 138, 139) are included into the group of clones of 1977 with abundant «flowering», harvest and high yield of strobiles). The clones that have the high and medium growth intensity, with high and medium flowering intensity, with high and medium yield of strobiles are perspective for seed plantations among the selected groups.

Analysis of the Variability of Floral and Pollen Traits in Apple Cultivars—Selecting Suitable Pollen Donors for Cider Apple Orchards

Most apple trees (Malus domestica Borkh.) are self-incompatible and fruit yield depends on cross-pollination between genetically compatible cultivars with synchronous flowering. Flowering intensity can vary strongly among years due to the biennial bearing habit of the cultivars. The knowledge of the phenological stages and floral and pollen characteristics is essential to select suitable pollen donors. We evaluated the phenotypic variability of flowering-related traits (i.e., flowering phenology, flowering intensity, pollen production and pollen quality) in 45 apple cultivars over two successive flowering seasons. Large phenotypic variability was found among the studied cultivars indicating that the local germplasm collection provides a good source of genetic and phenotypic diversity. However, low correlations were observed between floral biology traits and, consequently, the improvement in one trait seems not to affect other traits. Some of the cultivars such as ‘Perurico’ and ‘Raxila Dulce’ regularly produced copious amounts of high-quality pollen which can improve the pollen load dispersion leading to a most effective pollination process. We did not identify statistically significant correlations between pollen attributes and the biennial bearing phenomenon. The large variation in bloom dates from year-to-year observed under a typical Oceanic climate makes it advisable to combine cultivars in new plantings.

Phenotyping Flowering in Canola (Brassica napus L.) and Estimating Seed Yield Using an Unmanned Aerial Vehicle-Based Imagery

Phenotyping crop performance is critical for line selection and variety development in plant breeding. Canola (Brassica napus L.) flowers, the bright yellow flowers, indeterminately increase over a protracted period. Flower production of canola plays an important role in yield determination. Yellowness of canola petals may be a critical reflectance signal and a good predictor of pod number and, therefore, seed yield. However, quantifying flowering based on traditional visual scales is subjective, time-consuming, and labor-consuming. Recent developments in phenotyping technologies using Unmanned Aerial Vehicles (UAVs) make it possible to effectively capture crop information and to predict crop yield via imagery. Our objectives were to investigate the application of vegetation indices in estimating canola flower numbers and to develop a descriptive model of canola seed yield. Fifty-six diverse Brassica genotypes, including 53 B. napus lines, two Brassica carinata lines, and a Brassica juncea variety, were grown near Saskatoon, SK, Canada from 2016 to 2018 and near Melfort and Scott, SK, Canada in 2017. Aerial imagery with geometric and radiometric corrections was collected through the flowering stage using a UAV mounted with a multispectral camera. We found that the normalized difference yellowness index (NDYI) was a useful vegetation index for representing canola yellowness, which is related to canola flowering intensity during the full flowering stage. However, the flowering pixel number estimated by the thresholding method improved the ability of NDYI to detect yellow flowers with coefficient of determination (R2) ranging from 0.54 to 0.95. Moreover, compared with using a single image date, the NDYI-based flowering pixel numbers integrated over time covers more growth information and can be a good predictor of pod number and thus, canola yield with R2 up to 0.42. These results indicate that NDYI-based flowering pixel numbers can perform well in estimating flowering intensity. Integrated flowering intensity extracted from imagery over time can be a potential phenotype associated with canola seed yield.

Image-Based Phenotyping of Flowering Intensity in Cool-Season Crops

The timing and duration of flowering are key agronomic traits that are often associated with the ability of a variety to escape abiotic stress such as heat and drought. Flowering information is valuable in both plant breeding and agricultural production management. Visual assessment, the standard protocol used for phenotyping flowering, is a low-throughput and subjective method. In this study, we evaluated multiple imaging sensors (RGB and multiple multispectral cameras), image resolution (proximal/remote sensing at 1.6 to 30 m above ground level/AGL), and image processing (standard and unsupervised learning) techniques in monitoring flowering intensity of four cool-season crops (canola, camelina, chickpea, and pea) to enhance the accuracy and efficiency in quantifying flowering traits. The features (flower area, percentage of flower area with respect to canopy area) extracted from proximal (1.6–2.2 m AGL) RGB and multispectral (with near infrared, green and blue band) image data were strongly correlated (r up to 0.89) with visual rating scores, especially in pea and canola. The features extracted from unmanned aerial vehicle integrated RGB image data (15–30 m AGL) could also accurately detect and quantify large flowers of winter canola (r up to 0.84), spring canola (r up to 0.72), and pea (r up to 0.72), but not camelina or chickpea flowers. When standard image processing using thresholds and unsupervised machine learning such as k-means clustering were utilized for flower detection and feature extraction, the results were comparable. In general, for applicability of imaging for flower detection, it is recommended that the image data resolution (i.e., ground sampling distance) is at least 2–3 times smaller than that of the flower size. Overall, this study demonstrates the feasibility of utilizing imaging for monitoring flowering intensity in multiple varieties of evaluated crops.

Vegetative growth and productive performance of 'Abate Fetel' and 'Rocha' pear trees on quince rootstocks

The objective of this work was to evaluate the vegetative growth and yield of the 'Abate Fetel' and 'Rocha' pear (Pyrus communis) trees grafted onto the 'Adams', 'Ba29', and 'EMC' quince (Cydonia oblonga) rootstocks in the climatic conditions of Southern Brazil. The plants were trained on a central leader system, at a 4.0x1.0-m spacing. Vegetative growth, yield, and fruit size were evaluated. 'Rocha' showed greater vegetative growth, but also alternate bearing, mainly due to fructification problems. 'Abate Fetel' presented high flowering intensity, but a very low fructification, which limited its yield. Among rootstocks, 'Adams' induced a higher vigor during the initial stages and an increased intensity in flowering in the sixth year. In the following seasons, there was no rootstock effect on the assessed variables. 'Rocha' has a satisfactory production, whereas 'Abate Fetel' shows a weak vegetative growth and a very low production. The 'Adams', 'Ba29', and 'EMC' rootstocks induce similar vegetative and productive behavior in the 'Abate Fetel' and 'Rocha' pear trees.

Flowering phenology of apricot cultivars in the Belgrade region

The phenology of flowering was studied in 50 apricot cultivars in the Belgrade region over a period of eight years (2009-2016). Within the flowering phenophase, three sub-phases were registered: the beginning of flowering, full flowering and the end of flowering. In addition, the duration and abundance of flowering were examined. The average date of the beginning of flowering for all cultivars was March 22, of full flowering - March 25, and of the end of flowering - April 1. The average duration of flowering was 9.7 days, with a range among cultivars between 7.5 days ('Gergana') and 12 days ('Ninfa ' and 'Radka'). The lowest average score (3.0) for flowering intensity was obtained in 'Hungarian Best' cultivar, and the highest score (4.6) in 'Harcot' and 'Leskora' cultivars. In years with higher temperatures during the flowering, a smaller range in flowering time among cultivars was recorded, as well as shorter duration of flowering. Based on the beginning of flowering, the tested cultivars were classified into three groups: early-flowering (14 cultivars), medium-flowering (21 cultivars) and late-flowering (15 cultivars). Meteorological factors (air temperature) had a greater influence on the course and duration of the flowering phenophase than the genetic traits of the cultivars.

Influence of Rootstocks on Winter-Hardiness of Plum Generative Buds During the Wintering Period in Two Growing Regions

The selection of appropriate rootstock is the main precondition for obtaining a high yielding and sustainable plum orchard. In the Northern climate, plum overwintering is especially important, where winter hardiness of flower buds is one of indicators. This investigation was carried out during three wintering periods (2010–2013) at the Institute of Horticulture in Pūre (Latvia) and the Polli Horticultural Research Centre (Estonia), in orchards planted in 2001. The aim of the investigation was to evaluate the influence of different rootstocks on the viability of flower buds during winter for two plum cultivars in two growing regions. European plum ‘Victoria’ and hybrid plum ‘Kubanskaya Kometa’ grafted on eight clonal and eight seedling rootstocks were used in the investigation. Bud samples were taken two times during winter: end of January and end of March. The viability of flower buds and flowering intensity were determined in the laboratory. The viability was determined as dehydrogenase activity using triphenyl tetrazole chloride (0.5%), where in living cells the colourless substance due to enzymatic activity turns into a brightly coloured product — formasan. The optical density of colour was determined with a spectrophotometer at 485 nm. Both cultivars ‘Kubanskaya Kometa’ and ‘Victoria’ had higher flower bud viability in Polli compare to Pūre. In both growing regions, the highest activity of dehydrogenases for cultivar ‘Kubanskaya Kometa’ was on rootstocks ‘Myrobalan’, ‘St. Julien INRA 2’, ‘Wangenheims Zwetsche’ and for cultivar ‘Victoria’ — on rootstocks ‘Ackermann’, ‘Brompton’ seedlings, and ‘St. Julien d’ Orleans’. The dehydrogenase activity of in flower buds had a tendency to decrease during winter.