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.

The Roles of Floral Organ Genes in Regulating Rosaceae Fruit Development

The function of floral organ identity genes, APETALA1/2/3, PISTILLATA, AGAMOUS, and SEPALLATA1/2/3, in flower development is highly conserved across angiosperms. Emerging evidence shows that these genes also play important roles in the development of the fruit that originates from floral organs following pollination and fertilization. However, their roles in fruit development may vary significantly between species depending on the floral organ types contributing to the fruit tissues. Fruits of the Rosaceae family develop from different floral organ types depending on the species, for example, peach fruit flesh develops from carpellary tissues, whereas apple and strawberry fruit flesh develop from extra-carpellary tissues, the hypanthium and receptacle, respectively. In this review, we summarize recent advances in understanding floral organ gene function in Rosaceae fruit development and analyze the similarities and diversities within this family as well as between Rosaceae and the model plant species Arabidopsis and tomato. We conclude by suggesting future research opportunities using genomics resources to rapidly dissect gene function in this family of perennial plants.

Composition of Sexual Fluids in Cycas revoluta Ovules During Pollination and Fertilization

The composition of fluids that mediate fertilization in cycads is described for the first time. Using tandem mass spectrometry, proteomes of two stages of fluid production, megagametophyte fluid and archegonial chamber fluid production, are compared in Cycas revoluta. These were compared with the proteome of another sexual fluid produced by ovules, the pollination drop proteins. Cycad ovules produce complex liquids immediately prior fertilization. Compared with the pollination drops that mainly had few proteins in classes involved in defense and carbohydrate modification, megagametophyte fluid and archegonial chamber fluid had larger proteomes with many more protein classes, e.g. proteins involved in programmed cell death. Using high-performance liquid chromatography, megagametophyte fluid and archegonial chamber fluid were shown to have elevated concentrations of smaller molecular weight molecules including glucose, pectin and glutamic acid. Compared to megagametophyte fluid, archegonial chamber fluid had elevated pH as well as higher osmolality.

The Effect of Titanium Organic Complex on Pollination Process and Fruit Development of Apple cv. Topaz

Optimal weather conditions are necessary for the proper course of the flowering process and high activity of pollinators, which is the most important factor affecting pollination. Because weather conditions do not always favour effective pollination and because pollinators’ activities are decreasing, the application of compound stimulating pollination and fertilization may be a good perspective for increasing yield. Titanium is considered a beneficial element for plants. Preliminary studies have indicated the positive effect of titanium organic complex on pollen adhesion to the stigma and pollen germination on the stigma of tomato and cucumber. Therefore, a 2-year experiment was designed to determine the effect of titanium organic complex application on the pollination process and fruit development of apple cv. Topaz (Malus domestica Borkh.) The experiment demonstrated the positive effect of titanium organic complex on fertilization of ovules because of effective pollination, seed setting, and fruit development of apple. Application of titanium organic complex improved pollen adhesion to the stigma and pollen germination on the stigma. In addition, titanium organic complex increased the number of pollen tubes growing through the pistil style, which resulted in fertilization that was more effective, as confirmed by the higher number of seeds set in fruits. Higher numbers of seeds set in fruits positively affected their weight and size. Therefore, fruit harvested from trees to which titanium organic complex was applied were characterized by greater weight, length, and diameter compared to fruits obtained from the trees to which titanium organic complex was not applied.

Assessment of Fruit Drop in Different Cultivars of Litchi

Individual panicles produce hundreds of pistillate flowers but only a small proportion of these bear fruit and reach maturity. There are some stages of fruit drop during growth and development caused by different factors. An experimental trial was conducted in National Active Germplasm Site (NAGS) at ICAR-NRC on Litchi, Muzaffarpur, to assess the fruit drop due to different factors during 2014–2015. The result revealed that four factors viz., improper pollination and fertilization, embryo abortion, seed and fruit borer, and normal fruit abscission were associated with fruit drop in litchi and fruit drop varied from 23.53–77.54% with a maximum in Shahi and lowest in Elaichi during the first week of flowering. Fruit drop increased to 92.65–97.86% during the third week of flowering because of improper pollination and fertilization, and it reached a maximum level of 98.51–99.70% at the time of ripening stage with the lowest in Deshi. Embryo abortion was one primary cause of fruit drop during the 4th week whereas infestation of seed and fruit borer was the major factor for fruit drop during the 5–7th week. Such fruit drop can be controlled by managing the infestation of borer. Abscission due to ethylene production and heat stress during the maturity of fruit was yet another cause of fruit drop. This study will help to researcher to find out the time of infestation of seed and fruit borer which causes heavy fruit drop and it can be controlled with pest management option.

Effect of Genetically Diverse Pollen on Pollination, Pollen Tube Overgrow, Fruit Set and Morphology of Kiwiberry (Actinidia arguta)

Successful pollination and fertilization are crucial processes for obtaining a high yield, especially for dioecious plants such as A. arguta. Determination of pollen tube growth on stigma and fruit development parameters, which were investigated in this study, can enable the evaluation of male–female compatibility—one of the factors of successful pollination. Pollen quality and grain size were analysed for two years on six male cultivars of A. arguta and one of A. chinensis var. deliciosa. Results showed high pollen quality, both with parameters above 80%. Pollen germination in vivo showed differences in pollen–stigma interactions. The highest positive interactions were observed for all female cultivar crosses with male ‘Nostino’ and ‘Rubi’ and the lowest one for A. chinensis var. deliciosa ‘Tomuri’. However, fruit set and average fruit weight were equally high in most of the combinations (fruit set above 75% for the majority of combinations). Some differences were noticed in the average seed number per fruit and weight. All tested male cultivars were able to fertilize tested female cultivars, but taking into account other characteristics such as pollen efficiency, some male cultivars seemed to be more proper for commercial orchards. Using A. chinensis var. deliciosa pollen seems to be unreasonable in tested conditions.

Fruit formation of the distylous species Jasminum fruticans L. (Oleaceae)

The article presents the results of a comparative analysis of the fruit formation of long-styled and short-styled plants Jasminum fruticans L. (Oleaceae). The long-styled flowers have larger ovaries and ovules than short-styled ones. Visual signs of degeneration and reduction of the structures of the ovules were not detected. At the same time, the morphs of J. fruticans differ in fruit formation. The proportion of dimeric fruits with two seeds is greater in long-styled plants. Three periods of abortion of fruits/seeds were identified: (1) 1-7 days after flowering correspond to the stage of pollination and fertilization; (2) 8-14 days are the proembryonic stage of embryogenesis; (3) 15-35 days are the stage of globular embryo. The periods of fruits abortion are the same for long- and short-styled plants. Statically significant difference between morph was revealed in the first period of abortion. Differences in morphs of fruits formation indicate less effective pollination and fertilization in short-styled plans. The fruits of J. fruticans mature three months after flowering.

THE EFFECT OF DIFFERENT POLLINATORS ON FRUIT SET AND SOME FRUIT CHARACTERISTICS IN APPLE

Apple is one of the fruit species in which self-incompatibility is seen. For economical apple production, pollination and fertilization are required. In this study, it was aimed to determine effect of different pollinators on the fruit set ratios and some fruit characteristics of some apple varieties and apple genotypes originating from Kyrgyzstan by hybridization breeding method in 2020 year. According to the results, the highest fruit set ratio was obtained with the combination number 54 × 36 with 7.37%, while the lowest value was determined with the combination number 54 × 56 with 1.88%. Especially the precipitation that occurred during the fruit set time negatively affected the results. In the fruit characteristics results, the combination number 54 × 36 gave better results than the other combinations in fruit length and fruit width values. On the other hand, 21 × Elstar combination produced the best result in terms of WSDM (water solid dry matter) value and significant differences occurred between combinations in terms of seed number. Evaluating the obtained findings as a guide especially in the breeding studies to be made on apples and in the new orchards to be established may be beneficial for the producers.

About flowering phase of local pear sorts and their wild forms spread in Sheki-Zagatala region

In the article it is informed about typical characteristics of local pear sorts and their wild forms spread in Sheki-Zagatala region of Azerbaijan in flowering phase. During the research it was known that national selection sorts and wild forms of the pear devided into three groups for mass flowering period: quick flowering, medium term flowering, late flowering sorts. It was discovered that quick flowering sorts bloomed late, late flowering sorts bloomed quickly. Early spring months considered risky period of pollination and fertilization because of the changeable weather. Productivity depends on the level of pollination directly. The diversity of beginning and duration period on sort and forms has a positive effect to the productivity in Sheki-Zagatala region.

Theoretical Foundation of the Control of Pollination by Hoverflies in a Greenhouse

We propose a conceptual model for pollination and fertilization of tomato flowers in greenhouses crops by hoverflies, when the maximal number of adult pollinators maintained by the crops is less than what is needed for an economically successful pollination in greenhouses. The model consists of a two-stage process for additional feeding of hoverfly to maintain the pollinator density at the economically desired level. First, with a stochastic model, we calculate the density of flies necessary for the economically successful pollination, determined according to the economically expected yield. Second, using a deterministic optimal control model, we find a minimum cost supplementary feeding strategy. In summary, we theoretically demonstrate, at the present stage of the research without validations in case studies, that optimal supplementary feeding can maintain the economically desired hoverfly density.