Levels Of Fruit Set Research Articles

Combining pollination ecology and fine-scale spatial genetic structure analysis to unravel the reproductive strategy of an insular threatened orchid

In Vanilla species (Orchidaceae), the influence of sexual and asexual mating systems on the spatial structuring of population genetic diversity is understudied. These elements are crucial in restoration program to limit inbreeding depression and to maintain the genetic diversity of natural populations. In the remnant fragments of tropical dry forest in Mayotte (Comoros Archipelago, Indian Ocean), the clarification of the reproductive strategies of the orphan leafless Vanilla humblotii Rchb. f. will provide a better understanding of its fine-scale spatial genetic structure. Approaches combining reproductive biology and fine-scale spatial genetic structure analyses using ten microsatellite markers in 49 individuals sampled in the only remaining large population of V. humblotii were employed to unravel the reproductive strategies of this species. The results showed that V. humblotii displays unscented flowers and is allogamous and pollinator-dependent although also self-compatible. A total absence of pollen movements and a low level of natural fruit set (~1%) are reported, although a wild bee (Allodape obscuripennis Strand, Xylocopinae) and a bird (Nectarinia coquerelli, Nectarinidae) visited the flowers. A high genotypic diversity (G/N=0.88) and a phalanx clonal growth are detected, and seed dispersal is higher than pollen dispersal. The phalanx distribution of the repeated genotypes (ramets arisen from the same genet) is responsible for significant autocorrelations detected at small distances. Limited inbreeding was detected although geitonogamy could have been enhanced by vegetative reproduction. This study highlights the need to perform interdisciplinary studies to unravel the reproductive strategy of clonal plant species with a deceptive pollination system.

Addition of Forchlorfenuron to Spray Pollination Media Increases Fruit Set in ‘Hosui’ Japanese Pear

The effects on fruit set of adding forchlorfenuron (CPPU) to media in which pollen grains were suspended and used for spray pollination was investigated in ‘Hosui’ japanese pear (Pyrus pyrifolia). The percentages of fruit set after spray pollination were lower than those after hand pollination; however, media with 2 or 10 mg·L−1 CPPU used for spray pollination resulted in greater percentages of fruit set than media without CPPU. The media with CPPU also resulted in higher levels of pollen germination compared with the medium without CPPU; however, the number of seeds per fruit with CPPU treatment tended to be almost the same or less than for fruit without CPPU treatment. From these results, the higher levels of fruit set by CPPU might not be due to the high germination rate of the pollen grains but due to the induction of partial parthenocarpic properties. The medium with 10 mg·L−1 CPPU gave the highest levels of fruit set, but the fruit had abnormally thickened and enlarged calyxes, and the fruit shape tended to be deformed at ≈21 days after flowering. In addition, all of the harvested fruit were calyx-perpetual fruit in which the calyx remains until harvest time. Fruit treated with 2 mg·L−1 CPPU also yielded calyx-perpetual fruit with high frequency, but the fruit had normal calyxes and the fruit shape tended to be more normal. Thus, we conducted experiments focusing on the medium containing 2 mg·L−1 CPPU. Although the results were variable from year to year, more than 70% of hand-pollinated flowers set fruit during the 3-year study; this level of fruit production is sufficient for practical use. Thus, spray pollination using a medium with 2 mg·L−1 CPPU is an acceptable method for pollinating ‘Hosui’ japanese pear.

Pollination of Aosa rupestris (Hook.) Weigend (Loasaceae): are stamen movements induced by pollinators?

Inducement to stamen movement by oligolectic bees has been reported for some Loasaceae species; however, detailed research studies on the pollination ecology of species in the genus Aosa are absent. In this study, we analyzed the floral biology and breeding system of Aosa rupestris (Hook.) Weigend, focusing on the role of pollinators in inducing stamens’ movements. We described the anthesis, the behavior of floral visitors, and carried out reproductive experiments in a population in a dry forest (“caatinga”) area in Northeastern Brazil. We carried out four experiments and one control to establish whether the interval between the movements of two successive stamens is regulated by pollinator visits. Anthesis lasted for 3–4 days. Stamens (102 ± 12.57) remained with closed anther inside petals early in the anthesis, after which they moved to the center of the flower and presented its pollen (male phase). After all stamens have reached the center of the flower, the female phase started. Bicolletes nordestina Urban, 2006 was the only floral visitor to A. rupestris flowers, drinking nectar, collecting pollen, or sleeping on the flowers. Aosa rupestris was autogamous, but fruit set was higher under natural conditions. The interval between movements of two successive stamens was not different among experiments. Therefore, stamen movements were spontaneous and did not respond to pollinator visits, in contrast to the pattern of stamen movements observed in other Loasaceae species. Although A. rupestris is autogamous, floral structure and behavior of the oligolectic bee pollinator ensured the highest level of fruit set in this species.

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.

Insect inventories in a mango‐based agroforestry area in Bangladesh: foraging behavior and performance of pollinators on fruit set

AbstractInsect species inventories along with pest prevalence, foraging behavior of pollinators and their effect on fruit set of mango were studied in a mango‐based agroforestry area in Bangladesh during January to June 2013. Of 1751 collected insects, 11 species in five orders and nine families were pests, 13 species in six orders and eight families were predators and eight species belonging to three orders and seven families were found as pollinators. The pests exerted significantly higher abundance but lower diversity than pollinator, predator and other insects. The pollinator richness was found to be lowest but showed higher as well as similar diversity to other category insects. Three pest species prevailed throughout the season and hoppers showed significant abundance. Among the predators, ants were most abundant. Sulphur butterfly and syrphid fly revealed statistically identical and higher abundance than other pollinators. During the flowering season, pests were dominant and the abundance of insects was observed to peak at 11.00 h. The pollinators differed in their landing duration on flowers and their activity led to higher levels of fruit set. This study provides baseline information on insect abundance in an agroforestry system, which stresses the importance of conservation of beneficial insects.

Pollinator dependency, pollen limitation and pollinator visitation rates to six vegetable crops in southern India

We investigated levels of pollinator dependency and pollinator visitation rates to flowers of six vegetable crops: brinjal (aubergine), tomato, chilli pepper (Solanaceae), okra (Malvaceae), bitter and snake gourds (Cucurbitaceae) in six small family farms in the Coimbatore region of southern India. We tested the null hypothesis that fruit set in these crops would be independent of pollinators. We assessed fruit set through self and cross pollination by pollen augmentation, by pollinator exclusion and open pollination. We evaluated pollen limitation by comparing percentage fruit set by hand outcrossed pollen with open pollination; pollinator dependency by differences in percentage fruit set by open pollination and autogamous pollination; and visitation rates to flowers by pollinating insects. Tomato, chilli and okra produced self-compatible hermaphrodite flowers, with higher levels of autogamous fruit set (32-76%) and significantly lower levels of pollinator dependency (0-37%), whereas andro-monoecious brinjal and monoecious gourds had significantly lower levels of fruit set through autogamy, and higher levels of pollinator dependency. Pollen limitation was not evident in any crop. Diverse pollinating insects visited the flowers, and the frequency of visits by different pollinator taxa differed with crop type. Native vegetation and uncultivated land may enhance pollinator diversity in small farms.

Reproductive biology of Solanum vespertilio (Solanaceae), a zygomorphic, heterantherous, enantiostylous, and andromonoecious rare Canary Islands endemic

Without full knowledge of the reproductive biology of endemic species, the chances of effective conservation decline. We conducted multi-year field and laboratory studies of the sexual system and reproductive biology of Solanum vespertilio. Flowers are tetramerous, zygomorphic, heterantherous and sometimes enantiostylous. The species is andromonoecious. Anthers are heteromorphic in both sex forms, with one long upcurved and three straight shorter anthers. The style in male flowers is short to vestigial; in hermaphrodites it is strongly up-turned, longer than the anthers. The single large anther bears 45 % of the pollen. Some of these unusual features may illustrate insular release from selection, though, given the antiquity of the Canaries; they likely constitute selection to promote effective sexual reproduction and outcrossing. Experiments with manually deflected styles showed higher fruit set than controls. The nascent expression of enantiostyly offers the opportunity for understanding its evolution. The species is weakly self-compatible, which may offer fertility insurance, or be remnant of the status of colonizers. Field observations suggest that the number of fruit developing in an inflorescence affects the gender of subsequent flowers. Thus, the strength of andromonoecy may both affect the rate of outcrossing (genetic issues), and/or constitute a mechanism for response to the level of fruit set (physiological/ecological issues). Flowers were buzz-pollinated by large-bodied native bees. Most of the unusual features of S. vespertilio presumably promote effective pollen transport and perhaps outcrossing. Effective conservation programs depend not only on protecting habitat, but also on fruit set; the latter is dependent on knowledge of pollination and reproductive biology.

Self-incompatibility and pollination relationships for four Greek olive cultivars

The present three-year study aimed to (1) determine the number of flowers per inflorescence, (2) determine the proportion of hermaphrodite flowers and (3) investigate the genetic and environmental components of self-incompatibility through controlled pollination trials, followed by microscopic observation of in vivo pollen tube growth for olive cultivars ‘Koroneiki’, ‘Kalamata’, ‘Mastoidis’ and ‘Amygdalolia’. Significant differences between cultivars and years were observed for number of flowers/inflorescence and hermaphrodite flowers percentage. The highest number of flowers was observed for ‘Kalamata’ panicles followed by ‘Koroneiki’, whereas the lower numbers were for ‘Mastoidis’ and ‘Amygdalolia’. The highest percentage of hermaphrodite flowers was observed for ‘Koroneiki’, followed by ‘Kalamata’ while lower levels were counted for ‘Mastoidis’ and ‘Amygdalolia’. ‘Koroneiki’ showed a noteworthy capability (3.6–8.7% of hermaphrodite flowers) to set fruit through self pollination. Lower fruit set rates were counted for ‘Mastoidis’ (1.7–2.6%) and ‘Amygdalolia’ (0.5–2.4%). The lowest level of fruit set was observed for ‘Kalamata’ (0.4–2%). In the case of cross pollination, the highest fruit set rates were observed for ‘Koroneiki’, intermediate rates were counted for ‘Mastoidis’, followed by ‘Amygdalolia’, and the lowest levels of fruit set were counted for ‘Kalamata’. In the framework of the sporophytic SI system, we attributed R2R4 to ‘Mastoidis’ and ‘Kalamata’, R1R2 to ‘Amygdalolia’ and R4R6 to ‘Koroneiki’. Based on the results of these experiments, recommendations were released on cross pollination requirements and combinations with compatible cultivars for setting up new olive orchards to ensure high fruit sets and adequate yields.

SELF-INCOMPATIBILITY AND EFFECT OF RECIPROCAL CROSS AND OPEN POLLINATION ON FRUIT SET AND FRUIT CHARACTERISTIC IN JORDANIAN ALMOND LANDRACES

Limited studies were carried out to identify self- and cross-compatibility relationships among Jordanian almond landraces. Therefore, this study a imed at studying the level of self-incompatibility and the effect of cross and open pollination on fru it set and shell, nut and kernel related traits in almond. To achieve this objective, field experiment s were carried out during 2012 and 2013 cropping season on five Jordanian almond landraces and one wild bitter almond ( A. communis ) available in the farmer's fields at Ajloun district, Jordan. Fruit s et was recorded in the field after open-pollination , selfpollination by bagging the branches with flower bud s and cross pollination after emasculation of the floral buds. All almond genotypes showed complete s elf-incompatibility. Genotypes showed variable percentages in fruit set with similar trend in the two growing seasons. Following cross pollination treatment, genotypes exhibited fruit set ranging fr om 40.3% in Hajari to 94.0% in Fark and from 34.1% in Mukhmaly to 93.3% in Fark in 2012 and 2013, respectively. Results showed that cross pollination of Hami Hallo (79.7-81.7 and 77.8-89.2% in 2012 and 2013 respectively) and Fark (83.094.0 and 86.1-93.3% in 2012 and 2013 respectively) with other landraces led to high level of fruit set indicating high cross-compatibility. Slight differe nces were recorded in fruit set in reciprocal cross es. Pollen source did not affect shell, nut and kernel traits. As a conclusion, results obtained from this study showed that, all of the genotypes were self i n-compatible and all genotypes showed high level of cross-compatibility with variable degree among geno types.

Autonomous self‐pollination in the nectarless orchid Pogonia minor

AbstractThe pollination biology of the nectarless orchid Pogonia minor was investigated in central Japan. The investigation revealed that the solitary flowers failed to attract pollinators, while high rates of fruit set were observed in the natural population. Comparable levels of fruit set were obtained in bagged, artificial self‐pollinated and artificial cross‐pollinated plants, indicating that the species is not pollinator‐limited for fruit set under natural conditions. Autonomous self‐pollination in P. minor resulted from a reduced rostellum, which allowed contact between the pollinia and the stigma. Self‐pollination is thought to be an adaptive response that provides reproductive assurance under conditions of pollinator limitation. Since pollen limitation is generally known to be frequent among deceptive orchids, strong pollen limitation is probably a driving force in the autonomous self‐pollination mechanism in the nectarless orchid P. minor.

The first report of an alloheptaploid from the genusFragaria(Rosaceae)

AbstractHybrid recognition in the genus Fragaria (strawberry, Rosaceae) is difficult when based on morphological characteristics since there is great similarity among Fragaria species, even between different ploidy levels. This study aimed to identify and characterise an alloheptaploid hybrid (2n = 7x = 49) Fragaria for the first time in the genus from Europe (Germany, Bavaria) using different techniques. The hybrid was documented based on the evidence obtained from ploidy levels using flow cytometric measurement of nuclear DNA content, identification of the parental origin using 14 RAPD primers, fertility assessment from artificial crosses and fruit set level. RAPD analysis showed that the hybrid shared five species-specific markers with diploid F. vesca, and three with hexaploid F. moschata, indicating these species to be the most likely parents. The mean fluorescent intensity reflected by nuclear DNA in the putative hybrid (703) fell within the range accepted for heptaploidy in Fragaria, while the corr...

Depredación de arañas hacia visitantes florales y herbívoros, balance entre mutualismo y antagonismo

Fil: Tadey, Mariana. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Ecotono; Argentina

Assessment of self-(in) compatibility in some sweet cherry (Prunus avium L.) genotypes

The paper presents results of a three-year study of self-(in)compatibility in four economically important sweet cherry genotypes - ?Karina?, ?Kordia?, ?Regina? and ?Summit?, under agro-environmental conditions of Western Serbia. Determination of S-RNase genotype, microscopic observation of the pollen tube growth rate and assaying of the fruit set level after self-pollination were used to assess the genotypes. ?Kordia? (S3S6), ?Regina? (S1S3) and ?Summit? (S1S2) are self-incompatible genotypes, with a considerable number of pollen tubes ending the growth in the middle third of the style and lack of fruit set. ?Karina?, as S3S4 genotype, behaved as self-compatible, since its pollen tubes reached the base of the style and ovary, penetrating the nucellus. In addition, fruit set for ?Karina? was recorded in all three years of study (40.26%, 18.79% and 21.81%, respectively).

Ecosystems effects 25 years after Chernobyl: pollinators, fruit set and recruitment

Animals are assumed to play a key role in ecosystem functioning through their effects on seed set, seed consumption, seed dispersal, and maintenance of plant communities. However, there are no studies investigating the consequences of animal scarcity on seed set, seed consumption and seed dispersal at large geographical scales. We exploited the unprecedented scarcity of pollinating bumblebees and butterflies in the vicinity of Chernobyl, Ukraine, linked to the effects of radiation on pollinator abundance, to test for effects of pollinator abundance on the ecosystem. There were considerably fewer pollinating insects in areas with high levels of radiation. Fruit trees and bushes (apple Malus domestica, pear Pyrus communis, rowan Sorbus aucuparia, wild rose Rosa rugosa, twistingwood Viburnum lantana, and European cranberry bush Viburnum opulus) that are all pollinated by insects produced fewer fruit in highly radioactively contaminated areas, partly linked to the local reduction in abundance of pollinators. This was the case even when controlling for the fact that fruit trees were generally smaller in more contaminated areas. Fruit-eating birds like thrushes and warblers that are known seed dispersers were less numerous in areas with lower fruit abundance, even after controlling for the effects of radiation, providing a direct link between radiation, pollinator abundance, fruit abundance and abundance of frugivores. Given that the Chernobyl disaster happened 25years ago, one would predict reduced local recruitment of fruit trees if fruit set has been persistently depressed during that period; indeed, local recruitment was negatively related to the level of radiation and positively to the local level of fruit set. The patterns at the level of trees were replicated at the level of villages across the study site. This study provides the first large-scale study of the effects of a suppressed pollinator community on ecosystem functioning.

Partial fruit set failure phenomenon in ‘Nabbut-Ali’ and ‘Sabbaka’ date palm cultivars under hot arid climate as affected by pollinator type and pollination method

Partial fruit set failure phenomenon is one of the major problems that limit tree productivity of some date palm cultivars under hot arid regions. As an attempt to understand the nature of this problem, the effects of pollinator type and pollination method with bunch bagging following pollination on fruit set and bunch weight of ‘Nabbut-Ali’ and ‘Sabbaka’ date cultivars which are suffering partial fruit set failure were studied. The results showed that fruit set was not significantly affected either by pollinator type or pollination method in both cultivars during 2010 and 2011 seasons. Fruit set was higher in 2011 than 2010 season only in ‘Nabbut-Ali’ cultivar. In this respect, there were significant interaction effects between season and both of pollinator type and pollination method in ‘Nabbut-Ali’ cultivar. The pollinator ‘Hada-8’ produced lower bunch weight than all the other pollinators in ‘Nabbut-Ali’ cultivar. Also, the bunch weight was higher in the spray than in the traditional pollination. However, in ‘Sabbaka’ cultivar the bunch weight was not affected by pollinator type or pollination method. Bunch weight was higher in 2011 than 2010 season only in ‘Nabbut-Ali’ cultivar. The physical and biochemical quality characteristics of fruit were significantly affected by pollinator type and pollination method, upon cultivar, and were greatly lower in 2011 than 2010 season. Generally, under the conditions of Hada Al-Shame valley, neither of the used pollinators nor the pollination methods gave satisfactory level of fruit set in both ‘Nabbut-Ali’ and ‘Sabbaka’ date palm cultivars. Possibly, date palms have chilling requirements, upon cultivar, for subsequent normal flowering and fruit setting and this should be considered for each individual cultivar before cultivation in a certain region.

Determination and evaluation of superior self-compatible almond genotypes resulting from crosses between “Touno” and “Ferragnes” in Iran

Self-incompatibility is one of the most considerable difficulties in almond production, which reducing fruit set dramatically and making orchard management difficult. Therefore, breeding almond to produce self-compatible genotypes is very important. The purpose of this investigation was determination and evaluation of self- compatible and late flowering cultivars with good kernel characteristics in 38 almond genotypes resulting from crosses between self-compatible cultivar, Touno (male parent) and self-incompatible cultivar, Fragnees (female parent). Determination of self-compatible genotypes was carried out by investigation of fruit set levels, microscopic study of pollen tube after self pollination and PCR method. In addition, flowering and fruit characteristics were studied according to Gulcan descriptor. Genotypes number Tf23 and Tf6 were identified as very late flowering and self-compatible genotypes, in which their flowering time is coincidental with the very late flowering commercial cultivar, Tardi nonpariel. However, fruits of both genotypes were rather small. The highest fruit dry weight (4.24 and 4.06 g) was for self-incompatible genotype Tf28 and self-compatible genotype Tf15, respectively. These two genotypes had also the highest kernel weight being 1.16 and 1.13 g, respectively. Genotypes number Tf24 and Tf31 also had high dry weight fruit and kernel, which Tf24 had been identified as self-compatible, and Tf31 as self-incompatible genotypes. In genotypes Tf15, Tf31 and Tf24 fruit, nut and kernel had good qualities. The colour of nut and kernel of these genotypes were bright. Their kernels were uniform, smooth and sweet with low shrivelling. All fruits were full, with single kernel, which were in the same line as market demands. Investigations on fruit set level in field conditions revealed genotype number Tf23, with 18.23% on fruit set, as the most self-compatible genotype. Key words: Self-compatibility, self-incompatibility, fruit set, microscopic study.

Fitness inNarcissushybrids: low fertility is overcome by early hybrid vigour, absence of exogenous selection and high bulb propagation

Summary1.The evolutionary fate of natural hybridization is determined by the fitness of hybrids. Specifically, the survival of newly formed hybrids is affected by intrinsic genetic incompatibilities and/or genotype–environment interactions. The influence of these factors on the evolutionary potential of two natural hybrids ofNarcissushas been assessed. Fitness components were estimated in early experimental F1hybrids as well as in natural hybrids of unknown descent.2.To test the efficiency of reproductive isolation, fruit set, seed number and seed mass from interspecific crosses were measured, as were germination rate, radicle vigour and leaf appearance time in F1experimental hybrids in the greenhouse.3.Germination rate, survival and the number of leaves produced were also measured in F1plants transplanted to eight natural sites and compared with plants growing under greenhouse conditions. In addition, to overcome the difficulty of obtaining experimental late‐generation hybrids, fruit set, leaf production, bulb production and bulb size were measured in natural hybrids of unknown descent.4.Experimental crosses indicated weak post‐mating barriers. In the case ofN. cavanillesii,the barriers were virtually absent and interspecific crosses produced the same level of fruit set, seed set and seed mass as conspecific crosses. Fitness of F1experimental hybrids was similar to or greater than conspecific progeny, although some reciprocal hybrids differed on some of the traits measured. No differences were found in hybrid performance between the various natural sites and the greenhouse, indicating a lack of exogenous selection against hybrids. Mature natural hybrids of unknown descent exhibited higher levels of growth and bulb propagation than parental species but very low fertility.5.Synthesis.Hybrid vigour in early life stages and the absence of exogenous selection against hybrids provide an initial advantage for the establishment of hybrids in a wide variety of habitats. These factors, together with higher levels of growth and bulb propagation recorded in hybrids as compared to parental species, may compensate for low fertility, thus conferring evolutionary potential toNarcissusnatural hybrids.

Acerola pollinators in the savanna of Central Brazil: temporal variations in oil-collecting bee richness and a mutualistic network

We present parameters to support the conservation and management of Acerola pollinators. We monitored pollinator visits to this fruit shrub in a Brazilian savanna and identified the pollinator’s other food resources. Twenty-three species of pollinators were sampled. Although there were temporal variations in visitor frequency, satisfactory levels of fruit set were obtained. This temporal variation promoted a compensatory effect on plant reproduction as the pollinator species were replaced during the course of flowering. The analysis of pollen loads showed grains of 16 plant species and four pollen types belonging to seven families that formed a network with a nested pattern. Such a network suggests that generalist plants must be available in the crop vicinity. The data presented suggest the natural viability of cultivating Acerola in the savannas of Central Brazil and the importance of natural lands for providing nesting resources and to enhance the bee diversity in agroecosystems.

Tree growth and some other characteristics of new columnar apple cultivars bred in Holovousy, Czech Republic

Several characteristics related to tree growth, their fruitage and resistance against scab and powdery mildew were assessed during 2007–2008 on five new cultivars in comparison with the ancestral McIntosh Wijcik, in which 4 out of 5 had their pedigree. In several plots established between 1998 and 2006, the trees, which were on different rootstocks predominantly planted in spacing 4 × 0.5 m, were grown as vertical cordons practically without any pruning or shaping. Besides the first years after the planting these columnar trees generated very limited side branching. The cultivars mutually differ in tree vigour, spurring density, and size of fruiting spurs. Mean annual prolongation of central axes in the case of the trees on vigorous rootstocks varied within 30.8–57.5 cm, however, on M 9 rootstock it was distinctly shorter (23.4–34.1 cm). Beyond cultivar and rootstock the length of the annual prolongation was also significantly influenced by fruit set level. Trees of the Kordona cultivar were generally the most vigorous while those of Pidi were the weakest. The biennial pattern of bearing observed to an extent on nearly all the cultivars was connected with tendency to over-crop the trees. The highest annual yield equal to 10.3 kg was generated on trees of Kordona on MM 106, which corresponds to a total harvest of 25.7 t/ha. Cultivars Herald and Slendera possessed combined resistance both to scab and powdery mildew, whereas Kordona and Cumulus were resistant only to scab, but were in different degrees susceptible to mildew.

Analysis of the expression of partial self-incompatibility in almond (Prunus dulcis)

SummarySeveral pollination studies carried out on different, self-incompatible almond cultivars and seedlings have shown the presence of variable levels of fruit set following self-pollination that could be attributed to partial self-incompatibility (PSI). PSI is an intermediate reproductive behaviour, described in some angiosperm species, which indicates that self-incompatibility is a quantitative and plastic trait. The present study was performed to substantiate the occurrence of PSI in almond by studying ten cultivars that are traditionally considered to be self-incompatible (four of which had previously shown fruit set after self-pollination). These cultivars were analysed by microscopic observations of the progression of pollen tubes through the pistil following controlled self-pollination, determinations of fruit set after bagging flower buds, and molecular identification of the parentage of the fruits obtained using consensus PCR-primers for Prunus S-RNase alleles. The results showed that, in nearly all cases, the pollen tubes did not enter the ovary and, from a total of 5,349 bagged flower buds, only 17 fruits were obtained. In all cases, PCR analysis of the plants obtained after germination of these seeds showed a band corresponding to an S-RNase allele not present in the maternal progenitor, clearly indicating that they could only have arisen from cross-pollination.Therefore, the low fruit set values observed in some of the cultivars studied were not due to a breakdown in the self-incompatibility response that confers PSI, but to very low rates of contamination with foreign pollen. These results corroborate the self-incompatibility phenotype of the cultivars studied here, and highlight the importance of ascertaining the identity of the parentage in any progeny obtained after bagging.