Pollination Treatments Research Articles

The Patterns of Male and Female Flowers in Flowering Stage May Not Be Optimal Resource Allocation for Fruit and Seed Growth.

Changes in the proportions of male and female flowers in monoecious plants in response to external environmental conditions are directly related to the reproductive fitness of plants. The monoecious cucumber (Cucumber sativus) plant was used in this study to assess the responses of sex differentiation and the breeding process to nutrient supply and the degree of artificial pollination using pollen solutions of different concentrations. We found that the nutrient supply significantly improved the number of female flowers, while pollination treatments did not obviously increase the number of male flowers. Continuous pollination changed the number of female flowers especially in the later stage of the pollination experiment. Therefore, pollination changed the ratio of male and female flowers in the flowering stage of cucumber. Pollination treatment affected the fruit growth, seed set, and fruit yield. The number of fruit, fruit set percentage, and total seeds per plant did not increase with the pollination level, but individual fruit weight and seed number in one fruit did increase. The differentiation of male and female flowers in the flowering stage of cucumber is a response to nutrient and pollination resources, but this response is not the optimal resource allocation for subsequent fruit development and seed maturity, which suggests that the response of plants to external environment resources is short-term and direct.

Could the reproductive system explain the stability and long-term persistence in a natural hybrid zone of Petunia (Solanaceae)?

The long-term success of populations is dependent on individual reproductive success, and in general, increased population size and genetic diversity contribute to population maintenance, reducing the risk of local extinction. Interspecific hybridization has consequences that can vary according to the hybrids' fate, which can be strongly influenced by the reproductive capacity of hybrids and canonical individuals from the contact zone. We examined the reproductive biology and morphology of two closely related Petunia (Solanaceae) species and their interspecific hybrids from Serra do Sudeste, Southern Brazil, and we measured their reproductive success under controlled conditions based on seed production and germination from five pollination treatments. We found differences in self-compatibility degree among individuals, lineages, and pollination treatments based on high total seed production (> 204,000 seeds) and germination (630 seedlings evaluated). No correlation was observed between corolla colour and reproductive success or between floral morphological traits and compatibility. High self-compatibility and inter-lineage compatibility can explain the hybrid populations' maintenance and origin, favouring the two analysed species' introgression.

Is distyly in subtropical Psychotria brachyceras (Rubiaceae) similar to the general trends observed for the genus?

Distyly is a floral polymorphism that promotes cross-pollination through precise pollination. Psychotria is a mostly tropical genus of distylous Rubiaceae. Although widely studied in Brazil, some regions/species are still poorly explored, which hinders the understanding of distyly system along a greater geographical range. Here, we studied a subtropical population of Psychotria brachyceras in southern Brazil. For this, we characterized morphs occurrence, reciprocity of sexual structures, mating and incompatibility systems. In addition, we compared the reciprocity values from other species of the genus based on values gathered from literature to understand how the population behaves. The population showed equal proportions of thrum (short stigma/high anthers) and pin (high stigma/short anthers) morphs. Reciprocity was higher than the average for the genus and inaccuracy values between sexual organs were evenly distributed between the organ types, indicating a trend to typical distyly. Higher fruit set rates in intermorph and open pollination treatments and pollen tube growth observations confirmed that the population has a functional heteromorphic incompatibility system. Psychotria brachyceras showed no signs of distinct traits to typical distylous populations, which seems to ensure reproductive success and distyly maintenance.

Strategic use of honey bees (Apis mellifera L.) to increase the number and size of fruits in kiwifruit (Actinidia chinensis var. deliciosa)

Fruit size in kiwifruit depends mainly on the number of seeds or fertilized ovules. Pollination by wind is not enough to obtain a fruit size accepted by the market, so it is necessary to perform this practice by means of bees and/or artificially. Since there are controversies regarding the efficiency of each practice, the objective of this study was to determine the effect of pollination with honey bees, artificial-hand pollination and the combination of both methods, on fruit set at harvest, fruit size (length, minor and major diameter, weight), number of seeds, maturity and internal quality indexes (color, firmness, soluble solids content, dry matter, titratable acidity). The trial took place in the 2018/2019 and 2019/2020 seasons on a ‘Hayward’ kiwifruit orchard located in Miramar, in the southeast of Buenos Aires Province, Argentina. Treatments were applied in three uniform canes on 9 vines. Honey bee and combined pollination treatments showed a better fruit set at harvest (24.6% and 18.5% higher, respectively) compared to artificial-hand pollination. Also, the fruits originated from honey bee pollinated flowers and the combined treatment had higher length (4.8% and 5.4%), major diameter (5.5% and 5.7%), minor diameter (2.9% and 3.5%), weight (14.6% and 15.3%) and number of seeds (11.6% and 10.4%) with respect to those obtained by artificial-hand pollination. No significant differences were detected between treatments for maturity/quality indexes at harvest. Pollination with honey bees and the combined method were the most efficient. These results indicate that proper management of honey bees for kiwifruit pollination improves yield without affecting maturity, and preserving fruit quality indexes.

A test of the reproductive assurance hypothesis in Ipomoea hederacea: does inbreeding depression counteract the benefits of self-pollination?

Darwin proposed that self-pollination in allegedly outcrossing species might act as a reproductive assurance mechanism when pollinators or mates are scarce; however, in natural populations, the benefits of selfing may be opposed by seed discounting and inbreeding depression. While empirical studies show variation among species and populations in the magnitude of reproductive assurance, little is known about the counterbalancing effects of inbreeding depression. By comparing the female reproductive success of emasculated and open-pollinated flowers, we assessed the reproductive assurance hypothesis in two Mexican populations of Ipomoea hederacea. In one population, we assessed temporal variation in reproductive assurance for three years. We evaluated inbreeding depression on seed production, seedling germination, and dry plant mass by contrasting self- and cross-hand pollination treatments in one population for two years. The contribution of self-pollination to female reproductive success was high and consistent between populations, but there was variation in reproductive assurance across years. Inbreeding depression was absent in the early stages of progeny development, but there was a small negative effect of inbreeding in the probability of germination and the mass of adult progeny. Self-pollination provided significant reproductive assurance in I. hederacea but this contribution was variable across time. The contribution of reproductive assurance is probably reduced by inbreeding depression in later stages of progeny development, but this counter effect was small in the study populations. This study supports the hypothesis that reproductive assurance with limited inbreeding depression is likely an important selective force in the evolution of self-pollination in the genus Ipomoea.

Optimization of hybrid corn seed production in pollination systems at various parent seed planting ratios

The research was carried out on land belonging to the North Sulawesi Agricultural Technology Research Center located at the Agricultural Technology Research and Assessment Installation (IP2TP) Address Talawaan Bantik Village, Wori District, North Minahasa Regency in February 2021. This study aims to analyze the different effects of spray pollination treatment on the ratio female and male parents to increase hybrid corn seed production and to obtain the best pollination vs ratio between male and female parents in increasing hybrid seed productivity. This study uses a 2 x 4 Factorial Experimental Design where factor S consists of 2 levels and factor R consists of 4 levels in the RAK pattern, namely: Factor S = Pollination with 2 levels (S1 = Spray Pollination, S2 = Natural Pollination) and Factor R = Male to Female Planting Ratio (R1 = 4 female plants vs. 1 male plant, R2 = 5 female plants vs. 1 male plant, R3 = 6 female plants vs. 1 male plant, R4 = full female plants: solation of male plants) for each treatment repeated 3 times. Based on the analysis of interaction variance, spray pollination treatment at a planting ratio of 6 : 1 was able to increase the yield of hybrid corn seed production. The results of the 5% BNT further test showed the values obtained from observations of the number of rows filled with seeds, the number of seeds in a row, the weight of 10 cobs without husks and the weight of shelled 10 cobs in a row, namely, 12.1, 23.6, 1166.7, 867, 3.

Impact of Bee Pollination in Brinjal

Impact of bee pollination on brinjal (Solanum melongena L.) under protected condition was assessed with five pollination treatments viz., Apis mellifera L., Apis cerana F., Tetragonula iridipennis S., open pollination and control (pollinator exclusion). Comparative foraging activity and pollination efficiency index of the pollinators was recorded along with fruit production and quality parameters (fruit yield, length, diameter and weight, seed number and weight). Data revealed maximum pollination efficiency index (21) for A. cerana. The weight of fruit (96.30 g), diameter (56.54 cm), healthy fruits (53.89 %) observed with A. cerana was maximum. However, fruit length (15.10 cm), fruit yield (48.33 %) and seed weight (5.79 g) were found at par in all the pollination treatments. Significantly least crooked fruits (13.73%) were obtained when A. cerana was used, along with many folds increase in fruit set (26.69 %) and quality.

The pollination of the gynomonoecious Bdallophytum oxylepis (Cytinaceae, Malvales)

AbstractBdallophytum oxylepis is a rare and endemic species belonging to the Cytinaceae family, a root holoparasitic plant in which most resources are allocated to attracting pollinators. This species is gynomonoecious with intraindividual variation in flower size and sex. Moreover, the flowers exhibit sapromyophilous traits, as do other species of Bdallophytum. Firstly, this study aimed to determine whether all floral morphs can form seeds and be pollen donors (in the case of bisexual flowers). Secondly, as this species has floral traits hypothesized to adapt to particular types of pollen vectors (carrion flies), we also studied the pollination of B. oxylepis to confirm whether the syndromes correspond to what occurs in nature. Through pollination treatments, we determined that all floral morphs are functional. By monitoring the inflorescences, we found that pollination is specialized in the studied population. Stingless bees performed pollination, as they have a high visitation rate, frequency, and constancy, and they are unique visitors that deposit pollen on the stigmas. Thus, they appear to be effective pollinators rather than carrion flies, as predicted by the syndrome. As shown here, animal–plant interaction studies can help establish a basis for conserving rare species such as holoparasites. Moreover, knowledge about the reproductive aspects of B. oxylepis reveals essential clues about its life cycle and role in maintaining native pollinators with economic and cultural value, such as stingless bees.

Multiple lines of evidence supports the two varieties of Halenia elliptica (Gentianaceae) as two species

Delimiting species requires multiple sources of evidence. Here, we delimited two varieties of Halenia elliptica (Gentianaceae) using several lines of evidence, including morphological traits and mating system in a sympatric population, phylogenetic relationships based on nrITS and cpDNA (rpl16) data, and complete chloroplast genome sequences. Comparative analysis of 21 morphological traits clearly separates the two varieties of H. elliptica. Examination of the flowering process and pollination treatments indicate that H. elliptica var. grandiflora produces seeds via outcrossing, whereas H. elliptica var. elliptica produces seeds via mixed mating. Furthermore, hand-pollinated hybridization of the two varieties produced no seeds. Observations of pollinators showed that when bees began a pollination bout on H. elliptica var. grandiflora they preferred to continue pollinating this variety; however, when they began a pollination bout on H. elliptica var. elliptica, they showed no preference for either variety. Phylogenetic analysis confirmed the monophyly of H. elliptica, which was further divided into two monophyletic clades corresponding to the two varieties. A large number of variants from the chloroplast genomes reflected remarkable genetic dissimilarities between the two varieties of H. elliptica. We recommend that the two varieties of H. elliptica should be revised as two species (H. elliptica and H. grandiflora). Our findings indicate that H. elliptica varieties may have split into two separate species due to a shift in mating system, changes in flowering phenology and/or post-pollination reproductive isolation.

Pollination Biology of an Endemic Hawaiian Tree, Erythrina sandwicensis (Fabaceae: Papilionoideae), in a Novel Ecosystem1

Tropical dry forest ecosystems are among the most endangered ecosystems globally. In Hawai‘i, dry forest species are under threat due to habitat destruction, invasive species, and a loss of mutualisms including pollinators. Understanding the pollination biology of species at risk can inform conservation strategies. This study aimed to identify the breeding system and types of floral visitors to Erythrina sandwicensis (Fabaceae) or wiliwili, an iconic Hawaiian tree in decline and with little regeneration. We conducted hand-pollination trials and observed visitors in two sites: a botanical garden and a forest site. We compared fruit set, seed set, seed germination, seedling growth rate, and seedling size across four pollination treatments: open control, autogamy, geitonogamy, and xenogamy. We found that wiliwili is visited by a novel suite of non-native visitors. All treatments produced seeds, but the xenogamous (cross) treatment produced significantly more fruit and seeds than the control or other treatments. Seedlings produced from cross-pollinated treatments were also taller and had wider basal diameters after twenty-eight days of growth. These results indicate that wiliwili employs a mixed-mating system, and that trees are pollen limited. Enhancing current populations of wiliwili to promote cross-pollination could help increase population regeneration.

Pollination as a key management tool in crop production: Kiwifruit orchards as a study case

Despite the key role of pollination in the production of many crops, this is still one of the least understood factors in the orchard context. Pollen limitation, and impacts on crop production, is influenced by several potentially interacting factors such as crop or crop variety degree of dependence on cross pollination and on pollinators, diversity and abundance of the pollinator communities, landscape context and climate conditions. Understanding the pollination needs within an orchard is key to determine if the pollination is optimal or if it needs improvement. In some crops, such as kiwifruit, artificial pollination may be required where and when natural pollination cannot be improved or there is lack of pollen. In this study we quantified improvements to productivity resulting from artificial pollination and the efficiency of the technique for kiwifruit production and monetary gain on seven orchards distributed over the production range of this crop in Portugal. For that, we quantified orchard yield under 1) current natural pollination services, including pollination provided by wind and naturally occurring pollinator communities, 2) after artificial pollination and 3) under optimal pollination services. We characterized fruit production and key fruit traits such as fruit weight, size and caliber, and used production values, fruit caliber and respective market values to calculate the economic impact of pollination improvement. Results showed that pollen supply improved kiwifruit production in most orchards, either by changes in fruit set, fruit weight or both, and/or changes in fruit distribution by caliber and category. However, artificial pollination was not always efficient and/or needed. Contrarily to the expected, the artificial pollination treatment did not increase fruit weight but, in some orchards, it resulted in higher proportion of high-quality market fruits and/or lower proportion of unmarketable fruits. The changes in fruit traits translated into a tendency towards a small to moderate increase in monetary gain in four out of the seven orchards. This study reinforces the need to understand the current status of pollination services within the orchard context and to look at artificial pollination as a management tool in kiwifruit production. We conclude that pollination services in the study region might be sufficient to attain profitable yields; however, artificial pollination could be a useful tool under unpredictable pollination scenarios, but reviews of the efficiency of the methodologies used in this region are still necessary.

Floral biology and pollen grain presentation in “Arbequina” olive (Olea europaea L.) cultivar under non-traditional crop climatic conditions

ABSTRACT Olea europaea L. (Oleaceae), a traditional oil crop of Mediterranean basin, has been expanded considerably in the last decades to other regions of the world. “Arbequina” is one of the most widely planted cultivars due to its good agronomic and technological attributes, but interannual variability in thermal and rainfall regimes affects its regular fruit production in countries of the Southern Hemisphere, including Uruguay. To better understand the floral mechanisms that regulate fruit set in Southern Hemisphere climatic conditions, our work addresses the “Arbequina” flower functionality and pollen grains presentation along flower life span. In this andromonoecious species, the fruitful perfect flower morphs were evaluated by means of determining functional parameters such as stigmatic receptivity and pollen grain viability in each floral phenological stage, and pollen grain adhesion and pollen tube growth rate in hand pollination treatments. This flower morph did not show functional limitations under Uruguayan climatic conditions for the year in which the study was carried out, but a breeding system expressed by two different functional phases was detected. The first pistillate functional phase, where the stigma is receptive but no pollen release occurs, tends to avoid self-pollination and promotes crosspollination in the same flower. Then, a second perfectly functional phase follows, where the stigma remains receptive and the anthers release their pollen grains. In a self-incompatible olive cultivar such as “Arbequina”, this pollen grain presentation further stresses the importance of combining inter-compatible olive cultivars with synchronized flowering in orchard design, as a first step to ensure fruit set.

Three options are better than two: compensatory nature of different pollination modes in <i>Salix caprea</i> L.

Mixed pollination systems have been reported for many angiosperms. Here, we report on a dioecious willow, Salix caprea L., which employs three pollination modes, namely pollination by wind, nocturnal moths, and diurnal bees. In four field populations of S. caprea in Germany, we addressed the following questions: (a) How are the pollination modes affected by local mate availability? (b) What is the contribution of each pollination mode to seed set? (c) How does flower opening time affect pollination? We compared seed set among seven pollination treatments (wind pollination, diurnal pollination, nocturnal pollination, natural pollination, apomictic reproduction, daytime/night-time artificial pollination). Pollen limitation was observed across populations. On the other hand, limitations in mate availability affected the pollination modes differently. Insect pollination outperformed wind pollination in situations where nearby males were few or all positioned in the same direction from the females. The contribution of nocturnal moths was lower than that of the other pollen vectors. However, moth pollination worked complementarily with bee pollination in compensating for the lack of wind pollination. Furthermore, we found that the onset of flower anthesis peaked at sunset, and that cold night temperatures had no negative effect on seed set or pollen viability. Thus, nocturnal anthesis and prior pollination by moths may minimize male fitness loss due to pollen collection and grooming by bees. We suggest that S. caprea maximizes its fitness by combining multiple pollination modes that work in different environmental conditions, while optimizing the anthesis so that more pollen would be delivered to stigmas.

No Tradeoff in Fiber Quality with Increased Cotton Yield Due to Outcross Pollination

The societal and economic benefits of ecosystem services are both immense and multi-faceted. To holistically quantify the contribution of pollinators to agriculture requires measuring multiple indices of crop production beyond crop yield. Here, we conduct a field-based hand pollination experiment to measure the effects of self and outcross pollen on fiber yield and quality in conventionally managed cotton crops. First, we determine how different pollination treatments affect specific indices of fiber yield and fiber quality, including fiber length and fineness. Second, we investigate the suggested tradeoff between fiber yield and quality. We find that flowers receiving outcross pollen produce larger, heavier bolls than either self-crossed or non-crossed flowers. However, contrary to expectation, flowers of different treatments are indistinguishable in terms of fiber quality. Overall, we find that pollination treatment has no discernable effect on either fiber length or fiber fineness. Understanding the contribution of ecosystem services across multiple axes provides growers with information concerning potential tradeoffs or synergies, and offers insight into management decisions.

The Pollination and Fruit Quality of Two Kiwifruit Cultivars (Actinidia chinensis var. chinensis 'AU Golden Sunshine' and 'AU Gulf Coast Gold') (Ericales: Actinidiaceae) Grown in the Southeastern United States.

Kiwifruit is a new emerging crop for the southeastern United States that requires cross-pollination to set fruit. However, the pollination requirements for varieties grown in the southeastern United States are unknown. Through insect surveys and a bagging experiment, we assessed the pollination requirements of two female kiwifruit cultivars (Actinidia chinensis var. chinensis 'AU Golden Sunshine' and A. chinensis var. chinensis 'AU Gulf Coast Gold'). For each, fruit quantity (fruit set) and fruit quality (weight, size, seed count, firmness, soluble solid content, and dry matter) were compared among three pollination treatments (wind, insect, and artificial pollination). Low abundances of insects were observed visiting female flowers of both kiwifruit cultivars, and therefore likely minimally influenced kiwifruit pollination. Artificial pollination resulted in the greatest percentages of fruit set and marketable fruits, followed by insect and wind pollination. Artificial pollination resulted in fruits that were greater in weight, size, and contained more seeds, than insect- and wind-pollinated fruits. Firmness and soluble solid content did not vary greatly between pollination treatments, yet were greater in 'AU Golden Sunshine'. Dry matter content did not vary greatly between pollination treatments or between each cultivar. To maximize yields and optimize fruit quality, these results suggest that kiwifruit producers should place more effort into artificial pollination compared to wind and insect pollination. Future research should explore the use of managed bees (e.g., honey bees and bumble bees) within kiwifruit orchards to determine ways to utilize them as a secondary source for pollination needs.

Using RNA-seq to characterize pollen\u2013stigma interactions for pollination studies

Insects are essential for the reproduction of pollinator-dependent crops and contribute to the pollination of 87% of wild plants and 75% of the world’s food crops. Understanding pollen flow dynamics between plants and pollinators is thus essential to manage and conserve wild plants and ensure yields are maximized in food crops. However, the determination of pollen transfer in the field is complex and laborious. We developed a field experiment in a pollinator-dependent crop and used high throughput RNA sequencing (RNA-seq) to quantify pollen flow by measuring changes in gene expression between pollination treatments across different apple (Malus domestica Borkh.) cultivars. We tested three potential molecular indicators of successful pollination and validated these results with field data by observing single and multiple visits by honey bees (Apis mellifera) to apple flowers and measured fruit set in a commercial apple orchard. The first indicator of successful outcrossing was revealed via differential gene expression in the cross-pollination treatments after 6 h. The second indicator of successful outcrossing was revealed by the expression of specific genes related to pollen tube formation and defense response at three different time intervals in the stigma and the style following cross-pollination (i.e. after 6, 24, and 48 h). Finally, genotyping variants specific to donor pollen could be detected in cross-pollination treatments, providing a third indicator of successful outcrossing. Field data indicated that one or five flower visits by honey bees were insufficient and at least 10 honey bee flower visits were required to achieve a 25% probability of fruit set under orchard conditions. By combining the genotyping data, the differential expression analysis, and the traditional fruit set field experiments, it was possible to evaluate the pollination effectiveness of honey bee visits under orchards conditions. This is the first time that pollen-stigma-style mRNA expression analysis has been conducted after a pollinator visit (honey bee) to a plant (in vivo apple flowers). This study provides evidence that mRNA sequencing can be used to address complex questions related to stigma–pollen interactions over time in pollination ecology.

Somatic variants for seed and fruit set in grapevine

BackgroundGrapevine reproductive development has direct implications on yield. It also impacts on berry and wine quality by affecting traits like seedlessness, berry and bunch size, cluster compactness and berry skin to pulp ratio. Seasonal fluctuations in yield, fruit composition and wine attributes, which are largely driven by climatic factors, are major challenges for worldwide table grape and wine industry. Accordingly, a better understanding of reproductive processes such as gamete development, fertilization, seed and fruit set is of paramount relevance for managing yield and quality. With the aim of providing new insights into this field, we searched for clones with contrasting seed content in two germplasm collections.ResultsWe identified eight variant pairs that seemingly differ only in seed-related characteristics while showing identical genotype when tested with the GrapeReSeq_Illumina_20K_SNP_chip and several microsatellites. We performed multi-year observations on seed and fruit set deriving from different pollination treatments, with special emphasis on the pair composed by Sangiovese and its seedless variant locally named Corinto Nero. The pollen of Corinto Nero failed to germinate in vitro and gave poor berry set when used to pollinate other varieties. Most berries from both open- and cross-pollinated Corinto Nero inflorescences did not contain seeds. The genetic analysis of seedlings derived from occasional Corinto Nero normal seeds revealed that the few Corinto Nero functional gametes are mostly unreduced. Moreover, three genotypes, including Sangiovese and Corinto Nero, were unexpectedly found to develop fruits without pollen contribution and occasionally showed normal-like seeds. Five missense single nucleotide polymorphisms were identified between Corinto Nero and Sangiovese from transcriptomic data.ConclusionsOur observations allowed us to attribute a seedlessness type to some variants for which it was not documented in the literature. Interestingly, the VvAGL11 mutation responsible for Sultanina stenospermocarpy was also discovered in a seedless mutant of Gouais Blanc. We suggest that Corinto Nero parthenocarpy is driven by pollen and/or embryo sac defects, and both events likely arise from meiotic anomalies. The single nucleotide polymorphisms identified between Sangiovese and Corinto Nero are suitable for testing as traceability markers for propagated material and as functional candidates for the seedless phenotype.

Modeling kernel weight of hybrid maize seed production with different water regimes

Kernel weight (KW) is the key to ensuring seed vigor in hybrid maize (Zea mays L.) production, and irrigation is important for ensuring KW in arid regions. Irrigation experiments were conducted in an arid region of Northwest China to investigate the effects of water deficit on KW, plant growth rate per kernel after silking (PGRKAS), lag phase duration (LPD), kernel growth rate during effective grain filling (KGREGF), and effective grain filling duration (EGFD), which included a 50% water deficit at the vegetative stage, and a 50% and 100% water deficit at the flowering and grain-filling stages in 2018 and 2019. A restricted pollination treatment and two defoliation treatments (three and six leaves were removed from the top 14 days after silking) were conducted under each irrigation treatment in 2019 to obtain a wide range of data on grain filling characteristics and aboveground biomass. The results showed that a 50% water deficit at the vegetative stage shortened EGFD and LPD in both years. The 50% and 100% water deficit at the grain-filling stage decreased KW, PGRKAS, EGFD, and KGREGF in 2019, but had no significant differences in each indices in 2018 due to heavy rainfall. We found a bilinear plateau relationship between relative KGREGF (RKGREGF) and relative PGRKAS (RPGRKAS) as well as a logistic relationship between relative EGFD and RPGRKAS/RKGREGF. Combined with the Jensen model to simulate biomass characteristic parameters (the maximum aboveground biomass, the day of year of the maximum absolute growth rate, and the initial growth rate), the KW–water model performed well in predicting the KW of hybrid maize seed production under different irrigation treatments. This research provides a quantitative method for modeling the KW of hybrid maize seed production, which considers the source-sink relationship under different water regimes in arid areas.

Natural hybridization between two butterfly bushes in Tibet: dominance of F1 hybrids promotes strong reproductive isolation

BackgroundIt has been recognized that a certain amount of habitat disturbance is a facilitating factor for the occurrence of natural hybridization, yet to date we are unaware of any studies exploring hybridization and reproductive barriers in those plants preferentially occupying disturbed habitats. Buddleja plants (also called butterfly bush) generally do grow in disturbed habitats, and several species with hybrid origin have been proposed, based solely on morphological evidence.ResultsIn the present study, we test the hypothesis that B. × wardii is of natural hybridization origin in two sympatric populations of three taxa including B. × wardii and its parents (B. alternifolia and B. crispa) plus 4 referenced parental populations, using four nuclear genes and three chloroplast intergenic spacers, as well as with 10 morphological characters. Our results suggest that at both sites B. × wardii is likely to be a hybrid between B. alternifolia and B. crispa, and moreover, we confirm that most of the hybrids examined are F1s. That these plants are F1s is further supported by morphology, as no transgressive characters were detected. B. crispa was found to be the maternal parent in the Bahe (BH) population, from cpDNA evidence. However, in the Taji (TJ) population, the direction of hybridization was difficult to establish due to the shared cpDNA haplotypes between B. alternifolia and B. crispa, however we still predicted a similar unidirectional hybridization pattern due to results from cross-specific pollination treatments which supported the “SI × SC rule”.ConclusionsThe presence of mainly F1 hybrids can successfully impede gene flow and thus maintain species boundaries in parental species in a typical distribution of Buddleja, i.e. in disturbed habitats.

Investigating pollination strategies in disturbed habitats: the case of the narrow-endemic toadflax Linaria tonzigii (Plantaginaceae) on mountain screes

Plant mating systems may reflect an adaptation to a habitat type, with self-pollination being potentially common in unstable and disturbed conditions. We investigated the reproductive ecology of an Alpine, narrow-range toadflax, Linaria tonzigii Lona (Plantaginaceae), occurring in steep and dynamic mountain screes. We explored self-compatibility and spontaneous autogamy, seed viability, daily nectar production, pollinator behaviour and pollen transfer in wild populations, using hand pollination treatments, quantification of nectar volume, viability Tetrazolium assay, active pollinator sampling and video recordings, and UV-bright dust for pollen substitution. After ex novo sequencing of several genetic regions of L. tonzigii, we performed a multi-marker phylogenetic analysis of 140 Linaria species and tracked the occurrence of the self-compatibility trait. Our results showed that this species is self-compatible, pollinated mostly via spontaneous autogamy and pollinator-mediated geitonogamy, and self-pollinated seeds are as viable as cross-pollinated ones. Selfing could be due to pollinator rarity because, despite the studied species providing a high nectar volume, wild bees, moths and small beetles infrequently visited its flowers in the sparsely vegetated scree slopes. In addition, a preliminary survey showed a low genetic haplotype diversity in the study plant. Moreover, the phylogeny shows that self-compatibility is scattered in the tree, suggesting the adaptive nature of this reproductive trait in the genus Linaria. This study supports for theories that high prevalence of selfing is an adaptation to environments unfavourable for cross-pollination, and particularly where pollinators are rare, such as in perturbed, poorly vegetated high-elevation habitats.