Cluster-Zone Leaf Removal and GA3 Application at Early Flowering Reduce Bunch Compactness and Yield per Vine in Vitis vinifera cv. Pinot Gris

Compact bunches have been often associated with higher susceptibility to Botrytis cinerea and therefore reduction in berry quality in grapevine. The objective of this study was to evaluate three management methods (early leaf removal, gibberellic acid, and their combination) for reducing bunch compactness in Vitis vinifera cv. Pinot gris trained in two different training systems with contrasting vigor (Guyot and pergola). Treatments were applied at BBCH 62 or BBCH 65 and yield components, total soluble solids, fruit set, and bunch compactness parameters were evaluated. Both treatments individually reduced berry number, mean bunches weight and bunches compactness as well as yield per vine when compared to control-untreated vines. However, no major differences were observed when both the treatments were applied in combination for Guyot or pergola although a higher reduction in yield was detected for Guyot and a significant increase in total soluble solids was observed in pergola. Our study suggests that intense leaf removal and gibberellic acid applied at early flowering can help reducing bunch compactness in Pinot gris and showing it in two training systems. In particular, leaf removal represents a valuable alternative to plant growth regulators (i.e., gibberellic acid) as applicable in organic viticulture.

Viability of Embryo Sacs and Fruit Set in Different Plum (Prunus domestica L.) Cultivars Grown under Norwegian Climatic Conditions

Compatibility and synchrony between specialized tissues of the pistil, female gametophytes and male gametophytes, are necessary for successful pollination, fertilization, and fruit set in angiosperms. The aim of the present work was to study the development and viability of embryo sacs, as well as fertilization success, in relation to the fruit set of the cultivars ‘Mallard’, ‘Edda’, ‘Jubileum’, and ‘Reeves’, under specific Norwegian climatic conditions. Emasculated, unpollinated, and open-pollinated flowers were collected at the beginning of flowering, and on the 3rd, 6th, 9th, and 12th days after flowering, from all four plum cultivars over two years (2018/2019). Ovaries were dehydrated, embedded in paraffin wax, sectioned, stained, and observed under a light microscope. Results showed the existence of synchronization between successive phases in the development of the embryo sac and individual phases of flowering. All plum cultivars had higher percentages of viable embryo sacs, fertilized embryo sacs, and fruit set in 2018 than in 2019. These differences may be related to the very low temperatures during the post-full-flowering period in 2019, and to the low adaptation of some studied cultivars to unfavorable conditions. In our study, the cultivar ‘Jubileum’ showed the highest percentage of viable embryo sacs, fertilized embryo sacs, and fruit set compared to other cultivars, i.e., the best low-temperature adaptation.

Advancing Endodormancy Release in Temperate Fruit Trees Using Agrochemical Treatments

Endodormancy in temperate fruit trees like Prunus is a protector state that allows the trees to survive in the adverse conditions of autumn and winter. During this process, plants accumulate chill hours. Flower buds require a certain number of chill hours to release from endodormancy, known as chilling requirements. This step is crucial for proper flowering and fruit set, since incomplete fulfillment of the chilling requirements produces asynchronous flowering, resulting in low quality flowers, and fruits. In recent decades, global warming has endangered this chill accumulation. Because of this fact, many agrochemicals have been used to promote endodormancy release. One of the first and most efficient agrochemicals used for this purpose was hydrogen cyanamide. The application of this agrochemical has been found to advance endodormancy release and synchronize flowering time, compressing the flowering period and increasing production in many species, including apple, grapevine, kiwi, and peach. However, some studies have pointed to the toxicity of this agrochemical. Therefore, other non-toxic agrochemicals have been used in recent years. Among them, Erger® + Activ Erger® and Syncron® + NitroActive® have been the most popular alternatives. These two treatments have been shown to efficiently advance endodormancy release in most of the species in which they have been applied. In addition, other less popular agrochemicals have also been applied, but their efficiency is still unclear. In recent years, several studies have focused on the biochemical and genetic variation produced by these treatments, and significant variations have been observed in reactive oxygen species, abscisic acid (ABA), and gibberellin (GA) levels and in the genes responsible for their biosynthesis. Given the importance of this topic, future studies should focus on the discovery and development of new environmentally friendly agrochemicals for improving the modulation of endodormancy release and look more deeply into the effects of these treatments in plants.

Breeding System and Response of the Pollinator to Floral Larceny and Florivory Define the Reproductive Success in Aerides odorata

Consumption of pollination reward by felonious means in a plant species can influence the foraging behavior of its pollinator and eventually the reproductive success. So far, studies on this aspect are largely confined to interaction involving plant-pollinators and nectar robbers or thieves. However, a foraging guild in such interactions may also include floral herbivores or florivores. There is a paucity of information on the extent to which nectar larcenists may influence the foraging behavior of the pollinator and reproductive fitness of plants in the presence of a florivore. We investigated various forms of larceny in the natural populations of Aerides odorata, a pollinator-dependent and nectar-rewarding orchid. These populations differed in types of foraging guild, the extent of larceny (thieving/robbing), which can occur with or without florivory, and natural fruit-set pattern. The nectariferous spur of the flower serves as an organ of interest among the foraging insects. While florivory marked by excision of nectary dissuades the pollinator, nectar thieving and robbing significantly enhance visits of the pollinator and fruit-set. Experimental pollinations showed that the species is a preferential outbreeder and experiences inbreeding depression from selfing. Reproductive fitness of the orchid species varies significantly with the extent of floral larceny. Although nectar thieving or robbing is beneficial in this self-compatible species, the negative effects of florivory were stronger. Our findings suggest that net reproductive fitness in the affected plant species is determined by the overarching effect of its breeding system on the overall interacting framework of the foraging guild.

The rediscovery of Carya poilanei (Juglandaceae) after 63 years reveals a new record from China

Despite having been first published in 1941, Carya poilanei (A.Chev.) J.-F.Leroy is only known from three collections in Vietnam, Laos and Thailand. It has not been recollected since then and was long suspected to have become extinct through repeated deforestation events. Here, we report the rediscovery, and meanwhile the first new record in China, of this extremely rare gigantic hickory species at Yunnan province 63 years after its last collection in 1958. Three small patchy subpopulations were found with a total of about 50 adult trees having diameter at breast height (DBH) larger than 60 cm, together with some seedlings and saplings, but the fruit set was low. Based on new and fresh material, we present a revised morphological description of C. poilanei, and an updated distribution map for the species. In addition, we also provide a key for the hickories in China. Lastly, we suggest C. poilanei should be listed as a Critically Endangered (CR) species according to the latest IUCN Red List Categories and Criteria.

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.

Absorption and Distribution of Calcium (45Ca) Applied to the Surface of Orange (Citrus sinensis) Fruits at Different Developmental Stages

In this study, the rate of absorption and transport of calcium (Ca) in orange fruits (Citrus sinensis cv. Fukumoto) after surface treatment with 45Ca was evaluated by supplying treatments at different dates between fruit set and mid-phase II of growth (i.e., 30, 44, 66 and 99 days after full bloom, DAFB). 45Ca absorption was always detected, but 45Ca application at the fruit set was associated with the highest rates of Ca transport into the pulp (39%) compared to the other treatments (17–19%). Scanning electron microscopy SEM) images of the fruit surface showed the occurrence of stomata along with the entire rind at all the developmental stages evaluated. However, from the beginning of stage I, stomata began to collapse and develop plugs, and this became frequent as the fruit age increased. From 44 DAFB, oil gland density increased, and Ca oxalates (CaOx) were found in the fruit flavedo and albedo. Fruit Ca (not labeled) concentration increased from fruit set (30 DAFB) to 99 DAFB, although oil gland formation and rind growth and differentiation likely hindered Ca transport to internal fruit tissues (pulp). The total Ca concentration in the pedicel was always higher than that in the fruit, with no differences between the first three treatments. The information obtained in this study may be essential for improving Ca fertilizer efficacy in citrus by spray applications.

The Effective Pollination Period of European Plum (Prunus domestica L.) Cultivars in Western Norway

This study evaluated the effective pollination period (EPP) in four European plum (Prunus domestica L.) cultivars (‘Mallard’, ‘Edda’, ‘Jubileum’, and ‘Reeves’) during two years (2018–2019) under the environmental conditions in western Norway. The pollination of plum cultivars was carried out one, three, five, seven, and nine days after anthesis (DAA) with a pollen mix of two compatible cultivars (‘Victoria’ and ‘Opal’). Initial, middle-season, and final fruit set was recorded after one month and two months after pollination and just before the harvest, respectively. On average from both years cultivar ‘Jubileum’ had the highest fruit set when pollinated one, three, five, seven, and nine DAA (33.23%, 30.83%, 8.47%, 3.08%, and 1.15%, respectively), which was more than two folds higher fruit set than in the other studied cultivars. Cultivar ‘Jubileum’ showed significantly reduced fruit set between pollination on five and nine DAA, while cultivars ‘Mallard’, ‘Edda’, and ‘Reeves’ had markedly reduced fruit set if pollinated three to five DAA, implying that the EPP in ‘Jubileum’ was five days while in the rest it was three days. Variation of weather conditions during the flowering period in both years did not have a major effect on the receptivity of stigmas in the studied plum cultivars, which means that the existing differences in the length of EPP is maternal-genotype dependent.

Assessment of weather effect on flower morphogenesis and fruit set in mango varieties in central India

A two-year field experiment was initiated in 2017-18 and 2018-19 years simultaneously to assess temperature on flower morphogenesis stages, flower sex ratio (hermaphrodite/staminate male flower) and fruit set in monoembryonic Langra and Amrapali varieties. Different dates of flower phenological stages viz., bud, panicle, bloom and flower initiation, pea, marble, egg, and maturity of fruits were recorded. The Langra variety exhibited bud initiation after mid December whereas Amrapali variety by the end of December. The range of mean maximum / minimum temperature as 26-31/10-12 °C promoted hermaphrodite flowers per panicle by 74 per cent in Langra variety, whereas range of 27-29/11-13 °C favored by 35 per cent in Amrapali variety. A positive and significant correlation between total number of flower / panicle and flower sex ratio in both the varieties suggested that higher temperature during initial flower phenologies improved number of hermaphrodite flowers. A mean minimum temperature for producing more number of hermaphrodite flower exhibited a range of 11-14 °C under central Indian conditions. Fruit set was maximum during pea stage and decline afterwards in marble and fruit maturity stages due to sudden rise in temperature at marble stage that caused in drop down of humidity thereby resulted in fruit drop in both the varieties.

Pistil Biology of ‘WA 38’ Apple and Effect of Pollen Source on Pollen Tube Growth and Fruit Set

‘WA 38’ (‘Enterprise’ × ‘Honeycrisp’) is an apple variety that is characterized by a peculiar self-thinning trait in which most of the fruitlets naturally shed within the first 8 weeks after bloom, leaving some clusters empty, but most with 1–2 apples. This study aimed to investigate potential causes for the relatively low fruit set observed in ‘WA 38’ by investigating its flower biology. This study comprised three objectives: (1) To characterize the effective pollination period (EPP) of ‘WA 38’ by studying stigmatic receptivity, pollen tube growth, and ovule longevity in ‘WA 38’ flowers, (2) to compare the pollen tube growth of 5 fully compatible pollinizer varieties in ‘WA 38’ pistils, and (3) to evaluate fruit and seed set resulting from controlled pollinations with 5 fully compatible pollinizer varieties. The results showed ‘WA 38’ EPP was approximately 3.2 days in 2019 and 1.4 days in 2020, and that differences in pollen sources did not attribute significant differences in fertility in ‘WA 38’ flowers. The results of this study suggest mechanisms other than pollination and fertilization, such as competition among fruitlets within a cluster or hormone signaling, may have a stronger impact on ‘WA 38’ fruitlet abscission.