Artificial Self-pollination Research Articles

Studying self-fertility in new black currant cultivars from the VIR collection in Northwestern Russia

Background. An important task is to search for and select highly self-fertile cultivars for plant breeding programs and for setting single-cultivar plantings in commercial horticulture.Materials and methods. Cultivars were assessed for their self-fertility levels at Pushkin and Pavlovsk Laboratories of VIR in 2019–2022. Thirty black currant cultivars of eight genetic groups served as the research material. Their levels of self-fertility were tested using conventional techniques. Free pollination served as the control. The resulting data were analyzed according to the main indicators crucial for precise characterization of a cultivar’s self-fertility level: fruit setting rate, berry weight, seed yield, and fertilization effectiveness. The data were statistically processed using Microsoft Excel and the guidelines by B. A. Dospekhov. Fruit setting rate, berry weight, seed yield and fertilization effectiveness were considered for each pollination variant.Results and conclusion. Cultivars with high and stable self-fertility levels were identified as potential valuable sources for breeding programs: ‘Partizanka Bryanskaya’ (k-45548), ‘Ben Gairn’(k-45524), ‘Litvinovskaya’ (k-45542), ‘Mushketer’ (k-45544), ‘Raduzhnaya’ (k-45549), ‘Ben Lomond’ (k-32611), and ‘Vertikal’ (k-45528). Cvs. ‘Partizanka Bryanskaya’ (k-45548), ‘Ben Gairn’ (k-45524), ‘Mushketer’ (k-45544), and ‘Vertikal’ (k-45528) may be used in single-cultivar plantings because they are able to set the same number of berries under natural self-pollination and free pollination. Natural self-pollination (autogamy) led to a decrease in the size of berries and the number of seeds in them. An increase in the main self-fertility indicators was observed under artificial self-pollination and free pollination.

Specific functions of single pistil S-RNases in S-gene homozygous Pyrus germplasm

Gametophytic self-incompatibility (SI) is regulated by S-allele recognition; that is, pollen in a style with the same S-genotype will undergo programmed cell death and stop growing so that it is unable to complete double fertilization, ultimately resulting in the SI response. S-RNase is the female determinant of SI in pear (Pyrus). In the Pyrus genome, there are two different S-RNase alleles at the S-locus, which generate two different S-RNase products in the pistil. The extracted S-glycoprotein is actually a protein complex. In this study, artificial self-pollination was conducted at the bud stage to overcome SI in ‘Huanghua’ (S1S2) pear. Seven plants homozygous for S1-RNase and four homozygous for S2-RNase were selected from the selfed progeny of ‘Huanghua’ by S-gene molecular identification biotechnology. We investigated the function of single S-RNases isolated from the pistils of S-gene homozygous Pyrus germplasm. The pollen of ‘Huanghua’ could smoothly pass through the style of the S-gene homozygous germplasm and complete fertilization. S-RNases were extracted from flower styles of different genotypes and used to treat different types of pollen. The S-RNase from ‘Huanghua’ completely inhibited the growth of S1S2, S1S1, and S2S2 pollen, while the S-RNase from homozygous germplasm allowed some S1S2 pollen and different single genotypes of pollen to continue growing. These results further validate the core events of SI including cytoskeleton depolymerization and programmed cell death. By iTRAQ-based proteomic analysis of style proteins, a total of 13 S-RNase-related proteins were identified. In summary, we have created reliable S-RNase gene homozygous germplasm, which will play a crucial role in further research on SI in pear and in the development of the pear industry.

The Xenia Effect Promotes Fruit Quality and Assists in Optimizing Cross Combinations in ‘O’Neal’ and ‘Emerald’ Blueberry

Cross-pollination can improve the fruit set and quality of blueberry (Vaccinium spp.) for growers and consumers. However, the xenia effect in southern highbush blueberry remains unclear. Therefore, we selected eight cultivars of southern highbush blueberry (Vaccinium corymbosum L., interspecific hybrids) and applied pollination treatments (i.e., artificial self-pollination, artificial pollination with mixed pollen, or artificial pollination with individual cultivar pollen) to explore the xenia effects on the fruit set and quality of ‘O’Neal’ and ‘Emerald’. Pollen viability tests indicated that all of the cultivars are capable of fertilization. The highest fruit set came from ‘Bluerain’ pollen for ‘O’Neal’, while ‘Gulfcoast’ pollen increased fruit set the most in ‘Emerald’. Principal component analysis revealed that the cross combinations ‘Emerald’ × ‘Gulfcoast’ and ‘O’Neal’ × ‘Gulfcoast’ optimized the external and interior quality of the fruit. SSR was applied to determine which pollen source yielded the most seedlings. Results indicated that ‘Emerald’ × ‘Gulfcoast’ and ‘O’Neal’ × ‘Bluerain’ increased seedling production. Our results demonstrate that the xenia effects of ‘Gulfcoast’ pollen may increase ‘Emerald’ yields and promote fruit quality, while pollen from ‘Bluerain’ or ‘Jewel’ can improve ‘O’Neal’ fruit quality and seed number. Hence, these cross combinations may be utilized in blueberry production to increase fruit set, yield, and quality.

Pollen–pistil interaction in self-pollinated and sib pollinated flowers of sunnhemp (Crotalaria juncea L.)

Pollen pistil interaction studies were carried out in six sunnhemp genotypes. Pollen viability percentage of the six genotypes ranged from 0.0 to 93.5% and pollen germination ranged from 0.0 to 84.0% at four different floral stages starting from bud to opening of a flower. The viable pollen grains were present at the later three stages of flower for globose type anthers, while the pollen grains were viable at the later two floral stages for heart shaped anthers. Stigma receptivity was high to very high during S3 and S4 stages. Artificial self-pollination and sib pollination with a mixture of pollen grains were carried out and in vivo pollen tube growth in the style was investigated using fluorescence microscopy. In self-pollinated pistils, eight hours after pollination, callose wall development was seen around the nucellus cell. However, under sib pollinated pistil, eight hours after pollination, pollen tube penetrated into embryo sac of an ovule. The formation of callose in self-fertilized pistil prevented fertilization and seed set. But sib pollinated flowers were fertilized normally and a seed set could be observed. The investigation proved the existence of self-incompatibility. Keywords: Sunnhemp, Crotalaria, Pollination, Self-incompatibility, Callose

Reproductive biology of Butia capitata (Arecaceae) under cultivation - indicators for the domestication of a threatened fruit tree

Butia capitata is a netropical palm that has ecological and economic importance but is threatened by deforestation. The domestication of the species would contribute to its conservation and to income generation. However, there are gaps in knowledge about the phenology, floral biology and pollination of B. capitata and information on these topics is crucial to support breeding programs. We describe here the phenology and reproductive biology of B. capitata under cultivation and evaluated the storage potential of its pollen. Phenological and morphological evaluations of inflorescence and fruit development were carried out during both the rainy and dry seasons, the dynamics of anthesis and stigmatic receptivity were monitored and the reproductive system was experimentally evaluated. Pollen grain storage under different conditions was investigated for six months. Inflorescence emission were more rapid in the rainy season, with greater numbers of infructescences as well as fruit weight. Cross-pollination was predominant due to protandry, with a sterile period from one to six days. Cross- and open- pollination are the most efficient reproductive systems (46 and 47% fruting, respectively). Fruit fixation does not occur under spontaneous self-pollination or apomixis, while artificial self-pollination induces only a small fruiting rate. Pollen grain viability was maintained for 180 days under both refrigeration (4 °C) and freezing (-20 °C) conditions, but was less than 30 days under natural environmental conditions. The cultivation allows the production in the off-season of natural populations and pollen grain storage and artificial cross-pollination are promising possibilities for increasing the productivity of B. capitata orchards.

THE SELF-FERTILIZATION OF HONESUCKLE BLUE (LONICERA CAERULEAE L.) IN BELARUS CONDITIONS

The article presents the study results of five species of honeysuckle blue self-fertilization of derivatives in 2019–2020:
 from Lonicera caerulea subsp. kamtschatika – Zinri, Sinyavokaya, Pavlovskaya, L. caerulea subsp. altaica – Sirius, Selena.
 In the variations of free, natural and artificial pollination the fruit setting, the number of ripen fruits and the average fruit
 weight were evaluated.
 A high indicator of fruit setting (73.7–100.0 %) was established in the variations of free and artificial self-pollination.
 Despite the high setting, the number of ripen fruits in the self-pollination variations was 1.3–12.8 times less than in the
 free-pollination variation. When self-fertilized, cultivars Pavlovskaya and Zinri got undeveloped, seedless fruits, cultivar
 Selena presented weak development of ovaries, shedding of fruits at the stage of colouration, predominance of puny, small,
 unfulfilled fruits and seeds.
 The species Sirius and Sinyavokaya, which set more than 20 % of full-fledged fruits in the variations of natural and
 artificial self-pollination, were distinguished.

Investigation and screening of chrysanthemum resources to identify self-compatible mutants

Chrysanthemum (Chrysanthemum × morifolium) is an important horticultural crop with great ornamental and economic value. Most chrysanthemum cultivars are self-incompatible, which limits the creation of pure chrysanthemum lines which are the material basis for breeding and theoretical research. Here, artificial self-pollination and natural cross-pollination were used to analyze the self-compatibility (SC) and cross-compatibility (CC) of 85 chrysanthemums cultivated by our research group. By conducting a phenotypic study, observing of pollen germination in vitro and in vivo and gene expression analyses, we explored the reasons for the self-compatibility of chrysanthemum and identified self-compatible mutants. It was found that there were wide variations in self-compatibility among different chrysanthemum cultivars and the SC index ranged from 0 to 5.64, which could classify the chrysanthemum cultivars into three types: self-compatibility (SC index ≥ 1), self-incompatibility (SI, 1 > SC index > 0) and high self-incompatibility (SC index = 0). Seven chrysanthemum cultivars with self-pollinated progenies (‘Hongguan’, K183−8, A22, B12, D87, D76 and S8) were selected, and the pollen germination rates in vitro and in vivo were not significantly related to SC. The pollen tube of ‘Hongguan’ could pass through its own stigma and grow toward the embryo sac along the style, and there was no obvious inbreeding depression in self-pollinated progenies of ‘Hongguan’. In addition, we found that one S-locus receptor kinase (SRK), two S-locus cysteine-rich protein (SCR), two exocyst complex component EXo70A1 (Exo70A1) and one thioredoxin h-like 1 (THL1) were important for regulating self-compatibility of C. × morifolium. Our results not only laid a material foundation for creating pure lines through continuous self-pollination and analyzing the regulation mechanism underlying SC variation but also provided the possibility for theoretical research on the important ornamental traits of chrysanthemums in the future.

EVALUATION OF SELF-FERTILITY IN BLACK CURRANT CULTIVARS IN THE NORTHWEST OF RUSSIA

Background. High yield is one of the main requirements for modern black currant cultivars. It depends on many factors, but is always linked to self-fertility. Highly selffertile cultivars are of particular importance in areas with unfavorable weather conditions during flowering, because they are able to provide high yields even in single-cultivar plantings. In this regard, it is very important to study selffertility of cultivars in order to identify those with the highest level of this character for use in breeding and large-scale cultivation.Materials and methods. The study of selffertility was carried out at Pushkin and Pavlovsk Laboratories of VIR in 2014–2017. Fifty-seven black currant cultivars of different genetic and ecogeographic origin were the material of the research. The degree of self-fertility was measured by conventional techniques in 3 variants of pollination: 1) natural self-pollination; 2) artificial self-pollination; and 3) free pollination. Statistical data processing was performed using Microsoft Excel and the guidelines by B. A. Dospekhov.Results and conclusions. Highly self-fertile cultivars were identified, which may be recommended for breeders as sources of this trait: ‘Navlya’ (k-42228), ‘Dobrynya’ (k-42121), ‘Golubichka’ (k-32624), ‘Golosievsky velikan’ (k-44176), ‘Valentina’ (k-15631A), ‘Kozatskaya’ (k-44187), ‘Arapka’ (к-44175), ‘Kanakhama’ (k-44197) and ‘Fat’ (k-42509). High yield in the Northwest of Russia can be secured by cultivars that combine high self-fertility with large fruit size: ‘Valentina’ (k-15631A), ‘Vernisazh’ (k-43126), ‘Garmoniya’ (k-40677), ‘Dobrynya’ (k-42121), ‘Desertnaya Ogoltsovoy’(k-45670), ‘Joninai’ (k-43124), ‘Kanakhama’ (k-44197), ‘Karri (k-44172), ‘Mila’ (k-40673), ‘Sevchanka’(k-45551), ‘Sofievskaya’(k-43131), ‘Talisman’ (k-44183), ‘Yubileinaya Kopanya’ (k-44189), ‘Shalunya’(k-41988), and accession 2780-20-33 (k-15575A). It is shown that free pollination and artificial self-pollinationprovide a positive impact on the fruit setting level, fruit weight and seed productivity. Natural autogamy, on the contrary, tends to decrease the weight of berries and the number of seeds in them.

IMPROVEMENT OF SEED PRODUCTIVITY IN PARENTAL LINES OF F1 HYBRYD IN HEAD CABBAGE UNDER AN EFFECT OF STEROID GLYCOSIDES

Development of F1 cabbage hybrids is concerned to difficulties of artificial pollination, low ability to developovary leading to low seed productivity in parental lines. The aim of the study is to improve the seed productivity of self-pollinated parental line 3/14C for F1 cabbage hybrid ‘Krasotka’. Secondary plant metabolites such as steroid glycosides can help overcome these difficulties and increase the seed productivity (Blandinskaya et al., 2013). 3/14C-line was propagated by backcrossing flowers in bud stage with artificial self-pollination, using water solutions of steroid glycosides ‘Moldstim’ and ‘Melongozid’ (in concentrations 0.1%, 0.01%, 0.001% and 0.0001%). Seed productivity was evaluated according to methods that were elaborated earlier (Bukharov A.F. et al., 2011, 2013). It was established that all parameters of seed formation and development were increased significantly under treatment of steroid glycosides ‘Moldstim’ and ‘Melongozid’ in mentioned concentration. Differences were significant at the 5%-level of significance. Concentration of 0.001% was more effective than other both preparations. These preparations stimulated all phases of seed development. Number of fruits was increased by 16-39%, a number of seeds per one the pod was also increased by 17-38%, mass of 1000 seeds was increased by 9-12%. Thus, the seed productivity of parental line 3/14C F1cabbage hybrid named ‘Krasotka’ was increased by 44 to 105% as result of the action of steroid glycosides. Thus, ‘Moldstim’ and ‘Melongozid’ in concentration of 0.001% can be recommend as physiological stimulators to improve seed productivity in parental lines necessary for development of F1 cabbage hybrids.

Spatial and temporal variation on fruit set in <i>Epipactis</i> thunbergii (Orchidaceae) from southern Korea

ABSTRACT: Spatio-temporal variation in fruit set in orchids would affect long-term population viability and willinfluence genetic diversity over many generations. The aim of this study was to examine the breeding system ofthe nectariferous terrestrial orchid Epipactis thunbergii, to specifically determine levels of fruit set in terms oftime and space under natural conditions. We examined pollination under natural conditions and conducted handpollination experiments during a 2-year survey in four populations located along 1.5 km of coastal line in Jingui-ri (rual village) [Jeollanam-do (province), southern Korea]. We found that, over a 2-year period, levels of per-centage of fruit set were similar within patches of the four populations. By contrast, we detected significant dif-ferences in the percentage of fruit set among patches. We also found that plants with larger inflorescence sizeproduced significantly more fruits than plants with fewer flowers. Over a 2-year period, the percentage of fruitset for E. thunbergii was similar but low (14.1%) compared to that averaged for eighty-four rewarding species(37.1%). However, an increase in fruit set was achieved by hand-pollinations: artificial self-pollination (90.5−95.2%), artificial geitonogamy (94.7−95.0%), and cross-pollination (artificial xenogamy, 91.3−91.4%). Noemasculated flowers produced fruits and no automatic pollination was found in E. thunbergii. Our findings sug-gest that E. thunbergii is a self-compatible terrestrial orchid that depends on pollinators (insects) to achieve fruitset in natural habitats, and that local environmental conditions were similar over a period of 2 years in the studyarea. Our results also highlight the cryptic variation of fruit production in time, but more pronounced variabilityin space.

Influencia de la fuente de polen y su efectividad en la calidad de frutos de chirimoya (<i>Annona cherimola</i> MILL.)

Se evaluó la influencia de la fuente de polen y los horarios de polinización sobre el amarre y la calidad de frutos en 3 cultivares de chirimoya: ‘Campas’, ‘White’ y ‘Bonita’. El cultivar ‘White’ se cultiva comercialmente en California, mientras que ‘Campas´ y ´Bonita´ son cultivados, en menor escala, en España. Se realizó autopolinización y polinización cruzada artificial sin mezcla de polen en cada cultivar, en 3 horarios diferentes (07:00-09:00, 10:00-12:00 y 18:00-20:00 h), empleando la técnica del pincel. En todos los cultivares, el porcentaje de amarre de frutos con polinización natural fue bajo (de 5 a 10%). El tratamiento de autopolinización fue el menos eficiente, especialmente en ‘Bonita’ (47,90%). Por el contrario, cuando ‘Bonita’ fue usada como polen padre, el porcentaje de amarre de frutos fue significativamente alto en ‘Campas’ (85,83%) y ‘White’ (87,40%). Además, tuvo un efecto significativo al incrementar el peso del fruto, número de semillas, peso de semillas, peso de pulpa y simetría en los 3 cultivares.

Pollen viability, stigma receptivity and fruiting characteristics of botanical origin of Jinxianlian

The viability and life span of pollen were evaluated by TTC (2,3,5-triphenyl tetrazlium chloride) and the peroxidase solution, the stigma receptivity were estimated by benzidine-H2O2 method and the fruiting characteristics were investigated. The results showed that (1) Anoectochilus roxburghii and A. formosanus appeared the same up-and-down trend of the pollen viability, increased and then decreased. The storage temperature and storage time had significant impact on the pollen viability. With the extension of storage time, the pollen activity decreased. 4 degrees C refrigerator storage may be extended the pollen vitality. (2) The stigma had receptivity in 1st day and reached the highest level in the 4th day after blooming. A. roxburghii lost receptivity in the 8th day while A. formosanus lost receptivity in the 10th day after blooming. (3) The different pollination had significant impact on seed setting rate. The seed setting rate of artificial cross-pollination was higher than that of the artificial self-pollination. Collecting pollen in the 3rd day and carrying out artificial cross-pollination in the 4th day after blooming can significantly improve seed setting rate. The results provided technical assurance for A. roxburghii and A. formosanus breeding of new varieties and seed breeding.

Selffertilization in Campanula rotundifolia L. s. 1. group

Artificial selfpollination of six taxa of <i>C. rotundifolia</i> L. group was perfomed. More than 60% of the tetraploid plants and diploid <i>C. rotundifolia</i> s. str. representatives set seeds which germinated in some 42-76%. The seed setting in <i>C. serrata</i> was a little lower and the germination was very poor (0.07%). Only 18% of <i>C. cochleariifolia</i> plants yielded seeds after selfpollination. These seeds failed to germinate. The selfed offspring was viable only in part. Some developmental distur-bances were observed. A general tendency to reduction of height of stems and of the number of flowers per stem was also noted in successive selfed generations. A gradual decrease of pollen fertility was also observed. No tendency to gradual decrease of selfed seed fertility and germination was demonstrated. The factors preventing selffertilization proved to be efficient in <i>C. cochleariifolia</i> and <i>C. serrata</i>, but it seems that in nature they are strong enough even at a tetraploid level.

Conserving Open Natural Pollination Safeguards Jatropha Oil Yield and Oil Quality

The high oil content and suitable fatty acid composition of the seeds are two arguments to promote Jatropha curcas L. as a promising biodiesel crop. For seed yielding crops as J. curcas, it can be expected that successful pollination is a key process affecting oil yield and oil quality. Field experiments were conducted in Zambia to study the effects of different pollination treatments (autonomous autogamy, open natural, open pollen supplemented, self, and cross-pollination) on seed morphology, seed oil content (g), seed oil concentration (%), and oil fatty acid composition of J. curcas in 2- and 5-year-old plantations. For this experiment, 100 inflorescences per plantation were selected. Autonomous autogamy and self-pollination treatments reduced oil yield with 70 and 29 % respectively, compared to open pollination. Cross- and self-pollinations resulted in longer seeds than open pollination but did not affect oil content and concentration. The oil has high unsaturated fatty acid content (80 %) and is composed of nine fatty acids. Pollination treatments had an effect on fatty acid composition of oil from mature trees (5 years old), but had not for 2-year-old trees. The oleic acid content, a determinant fatty acid component for quality biodiesel production was lower for artificial self-pollination (9 % reduction) compared to open pollination. This research demonstrates that overall oil yield and quality are the highest under natural pollination. This shows the importance of safeguarding the quality and effectiveness of open natural pollination. This can be done by enhancing the presence of insects identified as J. curcas pollinators, particularly those pollinators enhancing cross-pollination.

FLORAL BIOLOGY AND BREEDING SYSTEM IN CARDIOCRINUM GIGANTEUM (LILIACEAE), A PERENNIAL BULBIFEROUS HERB IN YUNNAN PROVINCE IN CHINA

Giant lily (Cardiocrinum giganteum) is a perennial bulbiferous herb of Liliaceae and an endemic species in the eastern Himalayan region, which has become one of the new flower crops because of its high ornamental value. The floral biology and breeding characteristics of C. giganteum were studied by monitoring floral characteristics, duration of flowering, phenology, flowering behavior, outcrossing index (OCI), pollen-ovule ratio (P/O), pollen viability, stigma receptivity and fruit sets under a series pollination treatment. The result showed that flowering occurred from early May to early July and the mean duration of flowering was 16 days per inflorescence containing 6 to 19 flowers, and every flower has a life span of 7-11 days. The flowers were bisexual, with dichogamy and spatial separation. However, some anthers of a small number of flowers were longer than or equal to the stigma, which were suitable for self-pollination. The flowers were protandrous; the pistils matured in the day of floral opening. The pollen viability peaked around 75% after the pollen dispersed in 2 days, and its stigma had peroxidase activity from the third day after the anther loosing pollen until the end of flowering. The fruit setting rate of natural pollination was as high as 95%, that of artificial self-pollination 57.5%, and that of artificial xenogamy was as high as 100%, suggesting that C. giganteum is self-compatible. According to the artificial pollination experiments, OCI and P/O tests, the breeding system of C. giganteum was outcross and self-compatible, which needed pollinators.

Phylogenetic Relationship between Degree of Self-compatibility and Floral Traits in Lilium longiflorum Thunb. (Liliaceae)

Lilium longiflorum is endemic to the islands of the Ryukyu Archipelago in Japan and to the eastern seacoasts and satellite islands of the mainland of Taiwan. The species is an important ornamental plant, and is cultivated throughout the world. Lilium longiflorum has long been regarded as a self-incompatible species but the existence of selfing in some natural populations was suggested by isozyme analysis in a previous study. To confirm the occurrence of self-compatible individuals and to clarify the evolutionary shift of floral traits associated with degree of self-compatibility in L. longiflorum by comparative analysis, we used 17 populations of L. longiflorum, and two populations of L. formosanum, the genetically closest species of L. longiflorum, covering the entire species distribution. Artificial self-pollination revealed that not all L. longiflorum individuals are self-incompatible and there is substantial quantitative variation of self-incompatibility among L. longiflorum individuals and populations. Self-compatible dominant populations allopatrically and independently evolved at the periphery of the species distribution area, the northern Ryukyu Archipelago and Taiwan. Increasing degree of self-compatibility in L. longiflorum correlated with reduced corolla length, corolla width, corolla volume, and anther length for the Ryukyu Archipelago, in contrast to only reduced corolla width and volume for Taiwan. Approach between anther and stigma was not observed in any populations. Our data indicate that in the Ryukyu Archipelago increasing degree of self-compatibility evolved floral traits related to mating system evolution, to selfing, that does not depend on adjacency between anther and stigma position, but not in Taiwan.

Influence of Pollination Conditions on Fruit Set of Selected Blackcurrant Genotypes and Recently Released Cultivars

Fruit set of blackcurrant (Ribes nigrum L.) cultivars ‘Almo’, ‘ Ats’, ‘ Elo’, and ‘ Karri’ and four breeder's selections was investigated under open pollination, artificial, and natural self-pollination conditions in 2006–2007. The percentage of fertilized flowers, number of seeds per fruit, and fruit weight was largely genotype dependant, but it was also affected by the pollination conditions. All genotypes proved to be self-fertile, but the best fruit set occurred under open pollination conditions. There was a medium strength positive correlation between fertilization rate and fruit weight, and a below average positive correlation between the number of seeds and fruit weight.

Comparison of varying pollen source on productivity of sour cherry (Prunus cerasus L.) cultivars

Fruit set of five sour cherry cultivars (‘Újfehértói fürtös’, ‘Éva’, ‘Petri’, ‘Pándy 279‘ and ‘Csengôdi’) of eight years-old trees grown in Újfehértó, located in the Eastern north part of Hungary have been studied over two years (2008 & 2009). Following reciprocally cross-pollination, free-pollination, self-pollination (autogamy) artificial self-pollination (geitonogamy) were studied. The results show that both maternal and paternal parent cultivates had significant effects on the percentage fruit set. Significant differences have been found in fruit set among years and among pollination treatments. Fruit set of free-pollinated Pándy 276 cultivar was low and seasonally highly variable. The yield of this cultivar on self-pollinated flowers was nearly 0%, and in this treatment the maximum yields did not reach 10% in any of the examined cultivars. There was no significant relationship in the fruit set of free-pollination and natural self-pollination treatments.

Reproductive biology of Melaleuca alternifolia (Myrtaceae) 2. Incompatibility and pollen transfer in relation to the breeding system

The onset of stigma receptivity in Melaleuca alternifolia (Maiden & Betche) Cheel was evaluated by observing pollen-tube growth and seed set following controlled pollination. Pollen-tube numbers in the style, following controlled pollinations, increased from Day 1 to Day 6, then declining rapidly. The stigma was most receptive during Days 3–6, and still receptive at low levels as early as shortly after anthesis and as late as 10 days after pollination. The present study found that individuals of M. alternifolia differed in their degree of expression of self-incompatibility. Artificial self-pollination, with emasculation, in several families resulted in complete self-incompatibility, with no capsule retention. The microscopic observation of pollen-tube development revealed a mechanism of self-incompatibility in M. alternifolia. A self-incompatibility system operates in the style, although a few self-pollen grains are capable of germinating and producing pollen tubes. It also appears that late-acting self-incompatibility mechanisms discriminate against self-pollen tubes when they descend to the ovary. Artificial cross-pollination of selected parents produced seed with greater germination capacity and seedlings that grew faster than the corresponding open-pollinated seed and seedlings from the same parent. Freeze-dried pollen stored at −18°C maintained viability (22%) over 1 year of storage. This finding will allow greater flexibility in undertaking controlled pollinations, because stored pollen can be substituted for fresh pollen when insufficient quantities are available from new-season flowers. A wide variety of insects was observed visiting the flowers of M. alternifolia, and capsule set was high even in bags that excluded flower visitors greater than 2 mm. Thrips species seem likely to be important pollinators of this species because they are small and were abundant inside and outside of exclusion bags, although several other insect species such as bees, flies and wasps were also identified as frequent floral visitors.

Study on the mating compatibility of part pear varieties and wild types of Pyrus ussuriensis

To understand the mating compatibility of Pyrus ussuriensis Maxim., we studied the fertility of pollen and conducted a hand-pollination trial in the field on some pear varieties and wild types. The results showed that about 53% of varieties among 32 tested genotypes were male sterile. Not only did the pollen vitalities in normal varieties show distinct differences, but pollen vitalities from flower forcing in a glasshouse were found to be lower than those from natural flowering in the field, which had no apparent effect on fruit setting of tested varieties. Most of the tested genotypes such as Nanguoli, Pingxiangli, and Hanxiangli showed selfincompatibility (SI). Honghuagaili could bear fruit after hand pollination, but there were abnormal seeds in its fruits. So we suggested it was a recessive SI that happened during embryo development. Longxiangli has the capacity of self-compatibility (SC) to some extent, its fruit setting rate of inflorescence could reach 23.3%. Manual self-pollination during bud flowering could improve the fruit setting rate of part tested genotypes with SI, but had no effect on the fruit setting rate 3 days after flowering. Mating between female parents with the variety selected from F1 generation showed that the majority of their combinations were compatible. There was one-way SC when Nanguoli was crossed with Hanhongli, while no fruits could be found after Hanhongli was crossed with Nanguoli. It may be related to the S-genotype or haplotype of Nanguoli. In addition, mating between the varieties derived from bud mutation with the female parent appeared incompatible. We concluded that P. ussuriensis Maxim. is similar to other grown pear systems with the characteristics of SI, the fruit setting rate of self pollination in some varieties and wild types can be improved by artificial self-pollination during bud flowering, and fruit cannot be developed through pollination between the varieties from bud mutation and the female parent.