Fruit Set Values Research Articles

Flower scent, pollinators, and effects of proximity between plants on fruit set of the rare, threatened, and endemic Daphne rodriguezii

AbstractThis study focuses on Daphne rodriguezii, a threatened plant species that is endemic to Menorca in the Balearic Islands of the Western Mediterranean. The main objective was to investigate the volatile organic compounds (VOCs) in the floral aroma, as well as the timing and chemical variations in scent production. The primary pollinators were identified, and the relationship between their behavior and the chemical profile of the floral scent was investigated. Furthermore, the impact of plant density on fruit set rates was evaluated to obtain valuable insights for conservation and habitat‐management initiatives. The findings reveal that D. rodriguezii emits a distinct sweet floral aroma that primarily consists of benzenoids and linalool derivatives. Scent emission occurs during the evening and night, coinciding with the activity period of moths (Autographa gamma), which were identified as the primary pollen vectors for this self‐incompatible species. The fruit set values exhibit a positive correlation with the proximity between plants. These results emphasize the importance of moths and plant proximity as crucial factors to consider in the conservation management of this species.

Pollination biology of Gossypium turneri: Autonomous selfing provides reproductive assurance in an endangered wild cotton from Sonora, Mexico

AbstractThe wild cotton, Gossypium turneri, is a rare and endemic species from the state of Sonora, Mexico, threatened by habitat destruction, tourism development, and buffelgrass invasion in the municipality of Guaymas. As a consequence, G. turneri is now classified as endangered under Mexican legislation. This study aimed to document several aspects of the reproductive biology of this wild cotton to suggest conservation plans. The flowers of G. turneri remain open for only 1 day. Throughout the day, the flowers are visited by a diverse group of insects, including bees and butterflies. Pollination treatments revealed that this species is self‐compatible, capable of autonomous self‐pollination, and showed mixed evidence of pollen limitation. Although the flowers exhibit herkogamy, curved styles were observed that make the stigma come into contact with anthers. These results indicate that autonomous self‐pollination is caused by style curvature. Fruit set values and seed production per fruit in open pollinated control flowers were low, suggesting that this species produces a small number of seeds. These results provide new insights into this rare species, indicating that the species has a mechanism that provides reproductive assurance under low pollinator visitation, allowing for its persistence. The collection of seeds from the remaining populations for germplasm banks and the maintenance of live plants in botanical gardens are proposed for the conservation of this rare species.

The Effect of Different Pollinators on Fruit Set and Fruit Quality Parameters of Some Foreign Apricot Varieties in Kayseri Ecological Conditions (Central Anatolia, Turkey)

Turkey is among the rare countries in terms of plant diversity, and thus, most plant species spread widely throughout the country. Apricot is one of these plant species. Due to the self-incompatibility seen in apricots, it is necessary to use a pollinator variety for a quality and efficient product. With this study carried out in 2021 year, the effects of different pollinators on fruit set and some fruit quality parameters of Casne Drenova, Ninfa and P. de Tyrinthe cultivars were investigated in Kayseri ecological conditions. In the study, early ripening apricot varieties were used as paternal parent. According to the results of the study, it was shown that fruit set values varied between 11.6% and 22.6%. In the pomological parameters examined in the study, in general (except for fruit firmness), differences were found in combinations using different pollinators compared to the open pollinated fruits of the maternal parent. It is foreseen that the results obtained will be guiding especially in the breeding studies to be carried out with these varieties and in the establishment of new orchards.

Effect of soil and foliar application of micronutrients on growth and yield of guava (Psidium guajava L.)

The results of the present investigation clearly indicated that, different growth and yield parameters of guava were significantly influenced due to different treatments of micronutrients. The maximum increase in plant height (0.62m), shoot length (7.35cm) and tree spread (0.88m) was recorded with the soil and foliar application of 100g ZnSo4 + 100gFeSo4 + 25gBorax + 0.5%ZnSo4+ 0.5% FeSo4+0.2% Borax (T9) and at par results were obtained with soil and foliar application 50g ZnSo4+50gFeSo4+12.5gBorax+0.5%ZnSo4+0.5% FeSo4+0.2% Borax (T8). Regarding the yield parameters the maximum values of fruit set (67.76%), fruit retention (59.43%) and no. of fruits per tree (398.67) was recorded with soil and foliar application 50gZnSo4 + 50gFeSo4 + 12.5gBorax + 0.5%ZnSo4 + 0.5% FeSo4 + 0.2% Borax (T8) and at par results were noticed with the soil and foliar application of 100gZnSo4 + 100gFeSo4 + 25gBorax + 0.5%ZnSo4 + 0.5% FeSo4 + 0.2% Borax (T9). While, the average weight of fruit (155.37g) and yield (58.18 kg/tree and 16.18 t/ha) were recorded maximum with the soil and foliar application of 100g ZnSo4+100gFeSo4+25gBorax+ 0.5%ZnSo4+ 0.5% FeSo4+ 0.2%Borax (T9) and at par values of these characters were observed with soil and foliar application 50g ZnSo4+50g FeSo4+12.5g Borax+0.5% ZnSo4+0.5% FeSo4+0.2% Borax (T8).

Floral trait differentiation in Anacamptis coriophora: Phenotypic selection on scents, but not on colour.

Current divergent selection may promote floral trait differentiation among conspecific populations in flowering plants. However, whether this applies to complex traits such as colour or scents has been little studied, even though these traits often vary within species. In this study, we compared floral colour and odour as well as selective pressures imposed upon these traits among seven populations belonging to three subspecies of the widespread, generalist orchid Anacamptis coriophora. Colour was characterized using calibrated photographs, and scents were sampled using dynamic headspace extraction and analysed using gas chromatography-mass spectrometry. We then quantified phenotypic selection exerted on these traits by regressing fruit set values on floral trait values. We showed that the three studied subspecies were characterized by different floral colour and odour, with one of the two predominant floral volatiles emitted by each subspecies being taxon-specific. Plant size was positively correlated with fruit set in most populations, whereas we found no apparent link between floral colour and female reproductive success. We detected positive selection on several taxon-specific compounds in A.coriophora subsp.fragrans, whereas no selection was found on floral volatiles of A.coriophora subsp.coriophora and A.coriophora subsp. martrinii. This study is one of the first to document variation in phenotypic selection exerted on floral scents among conspecific populations. Our results suggest that selection could contribute to ongoing chemical divergence among A.coriophora subspecies.

Efficacy of Zinc Foliar Application from Different Sources on Productivity and Fruit Quality of Wonderful Pomegranate trees

Nanoparticles (NPs), especially from micronutrients, are recently motivated for replacing their common mineral counterparts. To evaluate their comparative efficacy, this investigation was conducted to estimate the impact of foliar application of zinc through different sources on productivity, fruit quality and improve marketable fruit of “Wonderful” pomegranate trees. The field experiment was performed during two seasons (2017 and 2018) on seven - year old pomegranate trees “Wonderful” cv., cultivated in a private “Hegazi” farm located at 57 km. from Cairo on the road to Alex., Egypt. Four sources of zinc named “Zinc Sulphate, Zinc mannitol complex, Bio-Nano zinc (Bio Zn NPs) and Zinc Oxide nanoparticle (ZnO NPs) with four rates from each other were sprayed twice (the first before one week from full bloom and the second after a month from the first). So the experiment included seventeen treatments in a sample study spread in a randomized complete block design by five replicates. Results explicated that the greatest significant values of fruit set% were recorded by Bio Nano Zinc (Bio Zn NPs) treatments especially (400 ppm Bio-Nano Zinc (Bio Zn NPs)). Spraying with (3000, 4000 ppm Zn mannitol complex) and (300, 400 ppm Bio-Nano Zinc (Bio Zn NPs)) showed significantly the greatest values of productivity, improves marketable fruits and fruit quality of “Wonderful” pomegranate trees. So it could be recommended by spraying “Wonderful” pomegranate trees by 3000 ppm Zinc mannitol complex or 300 ppm Bio-Nano zinc (Bio Zn NPs). Another important point is that the application of Bio Zn NPs fertilizer at around 10% from the commercial dose of zinc sulphate resulted in the same results without any change in the productivity, further researches are needed to study a further low level of Zinc Oxide nanoparticle (ZnO NPs) below (100 ppm Zinc Oxide nanoparticle (ZnO NPs)) which may be improving yield and fruit quality

Effect of Some Growth Regulators, Nutrient Elements and Kaolin on Cracking and Fruit Quality of Pomegranate ‘Wonderful’ Cultivar

This study was carried out during two successive seasons 2016 and 2017 on six years old ‘Wonderful’ pomegranate trees (Punica granatum L.). Trees were grown on sandy loam soil conditions in a private orchard located at Burg El-Arab, Alexandria governorate, Egypt. The trees were spaced 4x5 m apart and irrigated by drip irrigation system and received similar cultural practices adapted in the orchard. The effect of some growth regulators, nutrient elements and kaolin on cracking and fruit quality of pomegranate ‘Wonderful’ cultivar was studied. The experiment was designed as randomized complete block design with five replicates. Each block contained 11 treatments (control, naphthalene acetic acid (NAA) at 25 and 50 mg/l, gibberellic acid (GA3) at 100 and 150 mg/l, boric acid at 0.1% and 0.3%, calcium chloride at 1% and 2% and kaolin at 4% and 6%). Results revealed that, boric acid at 0.3% gave the highest mean values of fruit set (%), number of fruits/tree, yield (kg/tree) and anthocyanin; while, naphthalene acetic acid at 50 mg/l recorded the maximum mean values of fruit weight, fruit diameter, volume and grain weight, and gave the minimum mean values of fruit drop and fruit cracking (%). On other hand, gibberellic acid (GA3) at 150 mg/l gave the maximum yield (kg/tree), in the second season and the minimum fruit cracking (%), whereas, calcium chloride at 2% gave the best results of TSS (%), acidity (%), and vitamin C, total and reducing sugars were higher than the control for all treatments. Finally, kaolin at 6% gave the lowest percentage of sunburn and the highest percentage of juice, as compared with the control and other treatments during both seasons.

EFFECT OF SOME STIMULANTS ON FRUIT SET, YIELD AND FRUIT QUALITY OF HOLLYWOOD AND PIONEER PLUM CULTIVARS

The deterioration in area of plum orchards, in addition to the lack of productivity, resulted in an insufficient yield of plum. Some stimulants were investigated in this study during 2016 and 2017 seasons to improve fruit set; yield and fruit quality of Hollywood and Pioneer plum cultivars. Trees were treated with sprayed by with 1.0 and 1.5 ml/l of Daiblon k10 (contains 10% w∕w free amino acids and 10% w∕w potassium) or 4.0 and 6.0 ml/l of Essential Egy (contains mineral nutrients; natural Organic substance and 4.5 % L-amino acids). Other trees were treated with Humic acid as Actosol® (6.0 % w ∕ v potash and 20 % w ∕v Humate) at 5.0 ml/l /tree as spray foliar treatment or 30 ml/l /tree as soil application beside (control). The treatments were done at three times (at 30 % of flowering; 70% flowering and at full bloom) in each season. All trees were grown in sandy soil at El- Nubaria region, Behera Governorate, Egypt. A complete randomized block design was used with three replicates and each one was represented by one tree. During this investigation fruit set (%); yield (kg/tree); some physical and chemical fruit properties, as well as some mineral contents of leaves, were determined. Results cleared that the highest of both fruit number and yield (Kg∕ tree) were obtained when trees of Hollywood were sprayed with Essential Egy at 4.0 ml/l while the highest values of fruit set% and SSC were gained when trees were sprayed with 6.0 ml/l of Essential Egy. Spraying trees with Humic acid caused the highest leaf N and K content. All treatments under study gave variable effects on of total chlorophyll content. With regard to Pioneer cultivar, results showed that Essential Egy at 6.0 ml/l significantly increased fruit set %; fruit number per tree, yield (kg/tree and P content compared with Essential Egy at 0.4 ml/l which significantly increased SSC. Humic acid soil application significantly increased leaf N and P content. Spraying trees with Humic acid recorded the highest significant N and K content. Daiblon K10 at 1.0 ml/l gave the maximum total chlorophyll content. Thus, it can be recommended that spraying Hollywood and Pioneer cultivars with Essential Egy at 4.0 ml/l or 6.0 ml/l at three times (30 % of flowering; 70 % of flowering and at the full bloom) will increase plum yield and improve fruit quality

Reproductive ecology of Agave colorata: the importance of nectar-feeding bats and the germination consequences of self-pollination

Agave colorata is a paniculate agave distributed along the migratory route of the nectar-feeding bat Leptonycteris yerbabuenae. In this paper, we evaluate the importance of nectar-feeding bats in the reproduction of A. colorata in a population in Sonora, Mexico, and describe the germination consequences of self-pollination. We estimated abundance using five plots and set pollination treatments to evaluate the importance of bats. We recorded 14.8 ± 6.8 plants/400 m2, with a bimodal size distribution. Flowers are protandrous and visited mainly (> 20 visits/plant/30 min) by L. yerbabuenae. Pollination exclusion experiments showed that flowers excluded from diurnal visitors had maximum fruit set values (0.49 ± 0.42), while the autonomous self-pollination treatment had the lowest value (0.03 ± 0.06). Similarly, the greatest number of viable seeds per fruit was recorded in the diurnal exclusion treatment, while the greatest number of empty seeds was observed in the self-pollination treatment. Fruit set values among untreated plants varied from 32 to 54%, with a mean value of 41.8%. Seeds derived from self-pollination had a narrower window of opportunity for germination compared to seeds derived from nocturnal pollination. Self-pollinated seeds had lower germination, rate of germination or lag time in response to light, osmotic potential and heat shock treatments, compared to other pollination treatments, revealing an inbreeding cost. Overall, our results show that L. yerbabuenae is the likely major pollinator of the studied A. colorata population. However, under pollinator limitation A. colorata may produce seeds by autonomous self-pollination, at a cost expressed as lower germination.

Effect of Irrigation Scheduling under some Biostimulants Foliar Application for Navel Orange Trees on some Water Relations, Productivity, Fruit Quality and Storability in the North Nile Delta Region

A field investigation was performed during the two successive growing seasons 2014/ 2015 and 2015/ 2016 at a private orchard, located at Brembal, Motobus district, Kafr EL- Sheikh Governorate, Egypt, on twenty years old Navel orange trees budded on Sour orange rootstock spaced at 6*6 metres apart to study the effect of irrigation scheduling at (0.0, 0.8, 1.0 and 1.2 of EP) under biostimulants foliar application on productivity, fruit quality, storability and some water relations for Navel orange trees. The main results can be summarized as follows: The highest values for WA (seasonal water applied), CU (seasonal crop water consumed) and Ecu (consumptive use efficiency) were recorded under irrigation treatment I0(control) combined with Azospirillum compared with Jisemar, while, the lowest values were recorded under irrigation treatment (I1). I1 and I2 treatments have recorded the highest values of PIW(productivity of irrigation water) and WP(water productivity). Treatment I2 recorded the highest values of fruit set and the lowest rates of dropped, splitting and creasing fruits compared with the other treatments specially with Azospirillum while, the lowest irrigation level treatment (I1) showed the lowest rate of fruit set and the highest rate of fruit drop also, high irrigation levels (I0)gave the highest rates of splitting and creasing fruits compared with the lowest rates in I2. Results displayed a significant increasing of SSC% and SSC/acid ratio in fruits at the low irrigation level I1 when comparing with the low values in I0, as it was clear with Jisemar, whereas, acidity did not show any stable trend. Moderate irrigation level I2 recorded the high values of V.C and peel fruit firmness compared with the low values at I0 specially with-Azospirillum. Azospirillum application gave the high levels of chlorophyll with the high irrigation levels I0and I3compared with the lowest in I1,in contrast, I1 recorded the high rates of carotene than with I0, but Jisemar application was the most effective in that respect.. Treatment I2 combined with Azospirillum recorded the highest values of fruit number, yield(kg/tree) and ton/fed. during the two seasons, while I0 and I3 recorded the highest values for fruit weight than the others. During storage, I2 treatment recorded the best results on reducing fruit weight loss, limiting of fruit decay and maintaining the high levels of fruit firmness till the end of storage period specially with (Azospirillum) with a high significant differences. I2 and I1treatments recorded the high levels of SSC% and VC juice contents at the end of storage during the two seasons.

‘Manzanillo’ olive (Olea europaea L.) tree response to bioregulators and foliar urea application and its interaction with high temperatures

Para mejorar el amarre y rendimiento de frutos en árboles de olivo se evaluaron biorreguladores y urea vía foliar durante tres ciclos y su interacción con altas temperaturas. Además, se llevó a cabo un análisis empírico de la inf luencia de temperaturas altas sobre el amarre de frutos. No se encontraron diferencias estadísticas en rendimiento (un ciclo) entre los tratamientos evaluados. Sobresaliendo Cytokin, Maxigrow y el Testigo con rendimientos superiores a 6.2 t.ha-1, así como mayor número de inf lorescencias, aunque fueron estadísticamente iguales. Los mismos tratamientos mostraron mayor amarre de frutos y los tratamientos menos efectivos resultaron ser Urea y Agromil-plus. Destacaron en uniformidad Agromil-plus y Biozyme-TFen todas las variables evaluadas, mostrando valores altos en frutos normales-FN (100 y 99.1 %, respectivamente) y las más bajas relaciones de frutos partenocárpicos-FP (FP/FN). En dos ciclos se obtuvieron FN con valores muy altos (> 90 %) en todos los tratamientos. Del análisis empírico resultó que en el año con temperaturas > 27 °C, se obtuvieron sólo FP, mientras que en años con temperaturas > y < 27 °C, se lograron FN y FP. La ocurrencia de las altas temperaturas, al inicio o al final de la f loración, inf luye de manera importante en el amarre de frutos.

Factors affecting reproductive success in three entomophilous orchid species in Hungary.

The reproductive success of orchids is traditionally estimated by determining the fruit-set of individuals. Here, we investigated both the fruit and the seed production of three orchid species and the factors that may affect individual fruit-set, like pollination strategy, individual traits or the annual amount of precipitation. The species [Dactylorhiza sambucina (L.) Soó, Dactylorhiza majalis (Rchb.) P. F. Hunt & Summerhayes and Platanthera bifolia (L.) L. C. M. Richard] were studied in three consecutive years (2010-2012) in the Bükk Mountains, Hungary. All three species were proved to be non-autogamous by a bagging experiment. Data analyses showed significant differences between seed numbers but not between fruit-sets of species. There was no statistical difference in individual reproductive success between wet and dry years, however, the effect of the annual amount of precipitation is significant on the population level. Comparison of published fruit-set data revealed accordance with our results in P. bifolia, but not in D. sambucina and D. majalis. We assume that the surprisingly high fruit-set values of the two Dactylorhiza species may be due to the fact that the pollination crisis reported from Western European countries is not an actual problem in the Bükk Mountains, Hungary.

Differences in phenology and fruit characteristic between invasive and native woody species favor exotic species invasiveness

This study evaluates the idea that differences in reproductive phenology and traits between coexisting exotic and native species may promote exotic invasiveness. Reproductive phenology, proportions of flowers setting unripe fruits and ripe fruits (fruit set), abundance and morphology of fruits, and seed viability were compared between two invasive (Crataegus monogyna and Sorbus aucuparia) and six native woody fleshy-fruited species at three sites in temperate forests of northwestern Patagonia, Argentina. Flowering and the onset of fruit ripening occurred later in the exotic species than in most of the native species. The exotic species differed between them in some aspects of the reproductive process: C. monogyna had a higher fruit set, whereas S. aucuparia produced more flowers which offset its low values of fruit set. In both the exotic species and one simultaneously fruiting native species (Schinus patagonicus), high numbers of ripe fruits with a high proportion of viable seeds remained on the plants at a time when fruits of other native species were either scarce or absent (autumn–winter period). Compared to the fruits of S. patagonicus, those of both the exotic species are larger and fleshier. Therefore, the fruits of both the exotic species offer the dispersers, especially birds which were the most important frugivores in these studied temperate forests, a resource that would not be provided by the native plants. The success of these exotic species in Patagonian forests appears to be attributable in part to differences in their reproductive attributes such as fruit phenology and fruit traits such as size and fleshiness.

Reproductive outputs to floral trait variation in Nicotiana alata (Solanaceae) in Southern Brazil

Floral traits are useful for understanding how natural selection has acted upon the evolution of plants over short time spans and in restrictive ecological scenarios. Furthermore, the spatio-temporal dynamic of inter and intraspecific interactions acts in the individual’s fitness and contributes to floral traits’ evolutionary history. Nicotiana alata presents large white flowers typical of hawkmoth pollination. A population of N. alata was monitored between 2011 and 2012, and we observed differential reproductive rates throughout the flowering period, with substantially higher values of fruit and seed set at the beginning than at the end of the flowering season. There was an indication of pollen limitation in the middle of the reproductive season, with difference in seed set between natural and hand pollination. Decreasing longevity over time was observed, as were different reproductive rates between distinctive floral life times, with higher values of fruit set in 5-day flowers (88.8 %). These results may indicate density-dependent effects in reproductive outputs and intraspecific interactions as one of the potential ecological factors impacting flowering time. Furthermore, although the hawkmoths are recognized for their unpredictability, the visits’ efficiency may contribute to adequate pollen loads in flowers with shorter longevity.

Cuajado de frutos y partenocarpia en olivo Manzanillo con polinización cruzada.

The cross-pollination influence on the fruit set and parthenocarpy on twigs of ‘Manzanillo’ adult olive trees using different sources of pollen was studied. During two seasons (2004 and 2005) different sources of pollen (varieties) were applied to twigs of mature ‘Manzanillo’ olive trees, surface-irrigated and previously covered with cloth bags; pollen was hand-applied when previously tagged twigs showed 50-75% open flowers. On both years, fruit set was improved when ‘Sevillano’ (S) and ‘Barouni’ (B) pollen was applied, achieving higher values at the second season; lower fruit set values were obtained when using self-pollinated ‘Manzanillo’ (T) (2004) and ‘Mision’ (M) (2005) pollen sources. The cross-pollination increased the fruit set. The amount of FP ranged from zero to very low values during the 2004 season, whereas during the 2005 season values ranged from 5 to 70%. The benefits of using S and B pollen was observed by reducing the amount of FP fruits to lower than 10%, whereas using M pollen 70% of FP were obtained.

Mate limitation in populations of the endangered Convolvulus lineatus L.: A case for genetic rescue?

In self-incompatible clonal plants, the spread of individual plants can exacerbate mate limitation to the point that it becomes a serious constraint on long-term population persistence, especially in small, isolated populations. In such species, it may be necessary to introduce new genetic material from other populations to restore seed production, a strategy termed “genetic rescue”. In this study we assess the potential pertinence of such genetic rescue in the clonal perennial plant Convolvulus lineatus L., whose populations are often highly reduced in spatial extent and are currently being fragmented by land development projects in Mediterranean France. To do so, we quantify fruit production in a range of populations of different size over four years and perform a series of hand-pollination experiments in natural populations to assess whether fruit set is limited by mate availability. We found that C. lineatus is a self-incompatible species that shows extremely low values of fruit set in natural populations and that a principal cause of this low fruit set is a lack of compatible pollen. This may be primarily due to clonal spread that causes individual populations to be comprised of patches containing one or very few incompatibility types. In small populations fragmented by human activities and which show an absence of fruit production, we thus argue that genetic rescue represents a promising conservation management strategy to avoid inevitable long-term future population decline. We discuss how best to introduce new genetic material into the study populations.

Anomalous embryo sac development and fruit abortion caused by inbreeding depression in almond ( Prunus dulcis)

The decrease in fitness of the inbred offspring in relation to the outbred offspring is termed inbreeding depression, and is attributed to the expression of deleterious recessive alleles. This may represent an important problem for future almond growing, since the use of a very limited germplasm base as source of self-compatibility in breeding programmes has presumably led to a considerable increase of the inbreeding degree in subsequent progenies, from which new cultivars will be released. In the present study, the effects of inbreeding depression on flower morphology, pollen viability, pollen tube growth and fruit set were evaluated after self- and cross-pollination of two self-compatible almond cultivars and 12 descendants obtained from successive self-fertilizations. Moreover, in those descendants with very low or null fruit set values and in the cultivar ‘Tuono’ (first generation), the embryo sac development was studied. The self-compatible cultivar ‘Antoñeta’ was included as external control in the experimental assays. In general, there were no differences between both types of pollination, and only those individuals with higher inbreeding levels were affected by inbreeding depression, which was manifested by lower pollen germination, decelerated growth of pollen tubes through the style, delayed ovule development at the prezygotic phase, and high fruit drop. This high fruit drop seemed to be due to the presence of many aborted fruits with an anomalous postzygotic development of the embryo sac, finally resulting in necrosis at the chalazal end and lack of endosperm cellularization. Therefore, data presented here indicate that the low or null fruit set observed after fertilization in highly inbred almond genotypes seems to be a consequence of inbreeding depression, and highlight the importance of avoiding successive self-fertilizations as strategy of breeding in this species.

A comparative assessment of fruit formation in some orchid species from the southern Caucasus region

The distribution and population size of 5 orchid species (Cephalanthera longifolia, Orchis simia, Platanthera bifolia, Dactylorhiza romana, and Ophrys scolopax) were studied in the southern Caucasus based on the individual numbers in a given area. The fruit set was recorded for the latter 3 species and compared in natural and control groups (pollinators prevented) for D. romana and O. scolopax. We compared the obtained fruit set values with those reported from other regions. The distributions of the 5 species were completely fragmented and the population sizes were extremely small. This is the first report of O. scolopax from the region, recorded only in a remote location with a population of about 44 plants. The average fruit sets of D. romana and O. scolopax found in nature were significantly higher than those of the control groups (27% compared to 16%, N = 67, P < 0.001; and 10.4% compared to 3.04%, N = 44, P < 0.02, respectively). We located 20 plants of P. bifolia in 2 different locations with an average fruit set of 62.7%. Only 2 O. simia plants were found in the region. Our data show that pollinators have a significant role in the fruit sets of D. romana and O. scolopax and that the orchids studied require urgent conservation action.

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.

Breeding system and factors limiting fruit production in the nectarless orchid Broughtonia lindenii

Low fruit set values in most orchids (especially epiphytic and tropical species) are normally thought to be the consequence of pollination constraints and limited resources. In particular, pollination constraints are modulated by pollinator visitation rates, pollinator visitation behaviour (promoting crossing or selfing), the type and number of pollinia deposited on stigmas (in the case of orchids with subequal pollinia) and the amount of pollen loaded per inflorescence. In order to assess to what extent these factors can affect fruit set in specific orchid-pollinator systems, the repercussions of some of these aspects on reproduction of Broughtonia lindenii were examined in a coastal population in western Cuba. The study focused on plant breeding system, importance of pollen load and type of pollinia on subsequent fruit and seed, limiting factors of seed production and interaction with pollinators. This species presents long-lasting flowers that senesce after all forms of effective visit. Pollinator dependence for fruit production was demonstrated, while hand-pollination experiments revealed self-compatibility and inbreeding depression at seed level. More pollinia on stigmas enhance the proportion of well-developed seeds. In contrast, the pollinia type used in pollination is not important for seed quality of fruits, suggesting that small pollinia are not rudimentary. Natural fruit set in two consecutive years was substantially affected by pollinator activity, and also by systematic depredatory activity of ants and a caterpillar. Considering that this orchid completely lacks nectar and that the local assemblage of pollinators and predators influenced its reproduction, a minor importance of resource constraints in this epiphyte (with long-lasting reserve structures) is confirmed at least for a short time.