Field Pollination Research Articles

Viability fertility and SEM studies on cryopreserved pollen of cashew (Anacardium occidentale L.)

Abstract Cryopreservation can be utilized as an efficient and reliable tool for long-term conservation of cashew genetic diversity. This study aims at pollen germination in vitro, SEM studies, pollen cryopreservation and fruit set with cryostored pollen of cashew. Brewbaker’s and Kwack (1963) medium enriched with 30% sucrose and15% PEG elicited significant pollen germination in vitro. Madakkathara-2 recorded high viability profiles both with respect to fresh (90.32%) and cryopreserved (85.53%) pollen when compared to other genotypes and species. Anacardium othonianum recorded lower viability in fresh (40.97%) as well as cryopreserved (25.43%). The pollen grains were cryopreserved for six months and post viability assessment was carried out at regular intervals. Field pollination was carried and in vivo fertility was assessed using four month cryostored pollen. A fruit set range of13.17 to 30.67% and a seed germinability range from 37.75 to 63.64% was recorded. Both in vitro and in vivo results show the reliability of pollen cryopreservation, which can be effectively used in breeding and conservation of the cashew gene pool.

Decoding the black essence of Melianthus nectar.

This article is a Commentary on Magner et al. (2023), 239: 2026–2040.

Comparison of Pollen-Collecting Abilities between Apis mellifera L. and Bombus terrestris L. in the Oil Tree Peony Field

The lack of pollinators in the oil tree peony field was a serious problem for the seed yield. In the preliminary studies, we found that the seed rate of oil tree peonies was significantly improved by supplementing bees during the flowering stages in the pollination net room. In addition, the performance of Apis mellifera L. was better than Bombus terrestris L. To understand the interaction relationship between flowering characteristics and the managed bees, and the pollen-collecting ability of different species of bees, the flowering traits and the pollen loaded on bees were measured in this study. We found that the bees visited flowers with preference and they prefer to forage the flowers having pollen with higher viability. The B. terrestris carried more pollen (27,000.00 ± 5613.70 grains) on the body surface than that of the A. mellifera (7690.00 ± 2873.26 grains). The A. mellifera outperformed B. terrestris both in pollen deposition per visit on the stigma and on the pollen transfer efficiency. The viability of pollen on the body surface (67.77% ± 19.06%) and hind legs (92.02% ± 10.74%) of A. mellifera were both significantly higher than that of B. terrestris (31.84% ± 4.84% and 83.77% ± 6.40%). Our study indicated that the quantity and quality of pollen loaded on stigma by A. mellifera were both better than B. terrestris, which provided evidence that the A. mellifera was the effective pollinator pollinating for the oil tree peony in the pollination net room.

Optimizing the Working Parameters of Pneumatic Pollinators Based on the Kinematic Properties of Rice Panicles

Highlights An experimental platform for the kinematic characteristics of panicles was constructed. A regression model for the kinematic characteristics of panicles and working parameters was established. The multi-objective optimization based on the kinematic characteristics of rice panicles was carried out. The optimized combination of working parameters was verified by field pollination experiments. Abstract. Pollen shedding and dispersal processes are inextricably linked to the movement state of hybrid rice panicles. The purpose of this work was to study the effect of the working parameters of the pneumatic pollinator on the kinematic characteristics of hybrid rice panicles during flowering and to further optimize the working parameters of the pollinator. An experimental platform was built to characterize the movement of the panicle. Orthogonal experiments were conducted with airflow velocity, action position, and walking speed as experimental factors and kinematic parameters such as displacement, velocity, and acceleration of the rice panicle as experimental indicators. A quadratic regression model between the working parameters and the motion characteristics of the rice panicle was constructed and analyzed by analysis of variance (ANOVA). Matrix analysis was used for multi-objective optimization of the working parameter combinations. Field pollination trials were conducted for the optimized combination of parameters. The results showed that the coefficients of determination of the regression models were all above 0.85, which indicated good accuracy. The motion characteristics of the panicle, including the displacement maximum, velocity maximum, and acceleration maximum, can be maintained at a high level when the airflow velocity is 24 m/s, the action position is 120 mm from the top of the panicle, and the walking speed is 0.4 m/s. The field experiments showed that the optimization results could obtain the desired pollen density, distribution, and uniformity. This study can serve as a reference for the development of pneumatic hybrid rice pollination theory and the optimal design of the pollinator structure. Keywords: Hybrid rice seed production, Kinematic characteristics, Mechanized pollination, Multi-objective optimization.

Classification and Identification of S Haplotypes in Radish Based on SRK Kinase Domain Sequence Analysis

Radish is a typical self-incompatible crop. The rapid and accurate identification of S haplotypes can circumvent the blindness of the hybrid combination process, which is critical in radish heterosis utilization and the breeding of new varieties. In this study, based on the gene sequence which encodes the S-locus receptor kinase (SRK) of radish, and the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis, the S haplotypes were identified among 79 cultivated radish genotypes. The PCR results indicated that 79 radish genotypes could be divided into 48 Class I, 13 Class II, and 17 Class I/II S haplotypes. Sequence alignment confirmed that the Class I materials contained 19 S haplotypes, of which three haplotypes (‘NAU-S53’, ‘NAU-S54’ and ‘NAU-S55’) were identified for the first time in radish. After digestion using the Hinf I restriction endonuclease, the SRK domain of DNA fragments of different genotypes showed high polymorphism. Homozygous materials S haplotypes could be quickly distinguished by the differences in the digested bands. Molecular identification of the S haplotype was highly consistent with the field pollination and pollen tube germination results. These results would provide an important approach for the rapid identification of radish S haplotypes and the efficient utilization of self-incompatibility in heterosis breeding.

Development of an HRMA-Based Marker Assisted Selection (MAS) Approach for Cost-Effective Genotyping of S and M Loci Controlling Self-Compatibility in Apricot (Prunus armeniaca L.).

The apricot species is characterized by a gametophytic self-incompatibility (GSI) system. While GSI is one of the most efficient mechanisms to prevent self-fertilization and increase genetic variability, it represents a limiting factor for fruit production in the orchards. Compatibility among apricot cultivars was usually assessed by either field pollination experiments or by histochemical evaluation of in vitro pollen tube growth. In apricots, self-compatibility is controlled by two unlinked loci, S and M, and associated to transposable element insertion within the coding sequence of SFB and ParM-7 genes, respectively. Self-compatibility has become a primary breeding goal in apricot breeding programmes, stimulating the development of a rapid and cost-effective marker assisted selection (MAS) approach to accelerate screening of self-compatible genotypes. In this work, we demonstrated the feasibility of a novel High Resolution Melting Analysis (HRMA) approach for the massive screening of self-compatible and self-incompatible genotypes for both S and M loci. The different genotypes were unambiguously recognized by HRMA, showing clearly distinguishable melting profiles. The assay was developed and tested in a panel of accessions and breeding selections with known self-compatibility reaction, demonstrating the potential usefulness of this approach to optimize and accelerate apricot breeding programmes.

Multiple reproductive strategies of a spring ephemeral plant, Fritillaria maximowiczii, enable its adaptation to harsh environments

AbstractSpring ephemeral plants that experience harsh environments have developed specific reproductive characteristics. These characteristics are of great importance to the survival and reproduction of these species, particularly for rare and endangered plants. Fritillaria is a genus consisting of spring ephemeral plants with significant medicinal and ornamental value whose wild resources are highly threatened and whose reproductive characteristics and adaptative evolutionary mechanisms are still not well understood. Fritillaria maximowiczii is positioned at the most basal clade on the Fritillaria phylogenetic tree, whose reproductive characteristics remain obscure. In this study, we report the flowering dynamics, pollination biology and breeding system of F. maximowiczii. The flowering process of F. maximowiczii can be divided into seven stages. Based on the pollen/ovule ratio, the outcrossing index and a field pollination experiment on a natural population, F. maximowiczii showed high levels of outcrossing and self‐compatibility. Three types of pollinators were observed: two kinds of bumblebees, and spiders. Diverse herkogamy and dichogamy may have considerably improved its reproductive success rate. Furthermore, a special reproductive mode not previously reported in wild populations of Fritillaria, apomixis, was strongly suspected based on a high fruit setting rate (36.84%). Our study suggests F. maximowiczii has developed multiple reproductive strategies to adapt to harsh environments and ensure population reproduction, and the diverse reproductive mechanisms may be related to its primitive phylogenetic position in the genus. This study not only broadens our understanding of mechanisms of ecological adaptation in spring ephemeral plants but also provides key data for the conservation of Fritillaria.

Flowering characteristics and reproductive biology of Nymphaea hybrid, a precious water lily

Nymphaea hybrid is a precious aquatic plant of the family Nymphaeaceae that has esthetic, economic, medicinal, and ecological values. Owing to its spectrum of color, especially that of the rare blue strain of the genus Nymphaea, it has gained importance in the breeding of water lilies. However, the lack of research on its flowering characteristics and reproductive biology has severely hindered the reproduction and breeding of superior water lily varieties. In this study, the flowering phenology, floral characteristics, and flower-visiting insects of N. hybrid were assessed. The microstructures of stigmata and pollen grains were observed and the stigma receptivity was determined. Pollen viability was measured by an in vitro germination experiment. We also evaluated the breeding system by measuring the pollen/ovule (P/O) ratio, determining the outcrossing index (OCI), and performing field pollination experiments. The N. hybrid population flowered from late May to mid-November, with a flowering period of approximately 160 days. The florescence of a single flower ranged for 3‒5 days from June‒August and for 5‒10 days from September‒November. Inverse herkogamy and protogyny were exhibited by N. hybrid flowers. Stigmata were wet with papillae distributed on their surface, and the pollen grains were oblate with granular ornamentation of different sizes on their surface. The pollen germination rate was highest when they were deposited in a medium containing 5% sucrose, 0.001% boric acid, 1% agar, and 20 mg/L calcium chloride and cultured at 30 °C. Stigma receptivity was the strongest on the 1st day of floral anthesis, and pollen viability was the highest between 9:30 a.m. and 11:30 a.m. on the 2nd day of floral anthesis. The P/O ratio suggests that xenogamy is the main reproductive system. Artificial pollination results indicated that N. hybrid favored outcrossing and required the participation of pollinators, such as Bombus lucorum L. and Xylocopa s.str. valga Gerstaecker, both of which are effective bee pollinators. These results can aid in formulation and implementation of strategies for N. hybrid hybridization programs, and can also improve the controlled pollination efficiency for agronomic and ornamental purposes.

Low bee visitation rates explain pollinator shifts to vertebrates in tropical mountains

Evolutionary shifts from bee to vertebrate pollination are common in tropical mountains. Reduction in bee pollination efficiency under adverse montane weather conditions was proposed to drive these shifts. Although pollinator shifts are central to the evolution and diversification of angiosperms, we lack experimental evidence of the ecological processes underlying such shifts. Here, we combine phylogenetic and distributional data for 138 species of the Neotropical plant tribe Merianieae (Melastomataceae) with pollinator observations of 11 and field pollination experiments of six species to test whether the mountain environment may indeed drive such shifts. We demonstrate that shifts from bee to vertebrate pollination coincided with occurrence at high elevations. We show that vertebrates were highly efficient pollinators even under the harsh environmental conditions of tropical mountains, whereas bee pollination efficiency was lowered significantly through reductions in flower visitation rates. Furthermore, we show that pollinator shifts in Merianieae coincided with the final phases of the Andean uplift and were contingent on adaptive floral trait changes to alternative rewards and mechanisms facilitating pollen dispersal. Our results provide evidence that abiotic environmental conditions (i.e. mountain climate) may indeed reduce the efficiency of a plant clade's ancestral pollinator group and correlate with shifts to more efficient new pollinators.

Foraging Behavior of Honeybees (Apis Mellifera L.) and Ground Bumblebees (Bombus Terrestris L.) and its Influence on Seed Yield and Oil Quality of Oil Tree Peony Cultivar ‘Fengdan’ (Paeonia Ostii T. Hong et J. X. Zhang)

Abstract Oil peony (Paeonia spp.) is a new type of woody oil crop in China with a large cultivation area. Inadequate pollination is one of the main reasons for low seed yield. A pollination net room was built at an oil tree peony base, the numbers of honeybees (Apis mellifera L.) and ground bumblebees (Bombus terrestris L.) were artificially increased and the foraging behaviors and daily activities of the two bees on the plants were observed. Four different pollination methods (honeybee pollination, ground bumblebee pollination, natural field pollination and pollination without insects) were applied. The visit interval, single-flower visit time, number of single-flower visits, number of flowers visited per minute and number of stigma contacts were compared. Meanwhile, the effects of honeybee and bumblebee pollination on the oil yield and quality of peony seeds were compared. There were noticeable differences in daily activity between honeybees and ground bumblebees. Significant differences in the single-flower visit time, visit interval and visit frequency were also observed; honeybee and ground bumblebee pollination increased the seed yield of oil tree peony by 78.74% and 31.88%, respectively. Therefore, both honeybees and ground bumblebees are effective pollinators of oil tree peony. These results provide a theoretical basis for further utilization of bee resources for oil tree peony pollination.

Foraging Behavior and Pollination Efficiency of Apis mellifera L. on the Oil Tree Peony ‘Feng Dan’ (Paeonia ostii T. Hong et J.X. Zhang)

To solve the issue of insufficient pollinating of insects for the oil tree peony ‘Feng Dan’ (Paeonia ostii T. Hong et J.X. Zhang) and improve its seed set and yield, we conducted observations from 2017 to 2018 to investigate the relationship between honey bee (Apis mellifera L.) foraging behavior and diurnal activity. We compared the single-fruit seed set ratio among three flower types on the same plants of the oil tree peony, which flowered simultaneously, in three pollination areas (bee pollination, natural field pollination, and controlled pollination by pollinators) and in a net room under self-pollination, wind pollination and bee pollination. Apis mellifera exhibited short single visitations, long visitations to a single flower and repeated visits to flowers of the oil tree peony. The number of flower visits of A. mellifera was significantly and positively yet weakly correlated with the number of stigma visits (2017: r = 0.045, p < 0.05; 2018: r = 0.195, p < 0.01). The seed set of oil tree peony follicles in the A. mellifera pollination area was significantly higher than that in the natural pollination field area and the control net rooms. On the same oil tree peony plant with synchronous flowering, the percent seed set of follicles pollinated by A. mellifera at a high density was significantly higher than that resulting from wind pollination and self-pollination.

3.1 Which endpoints can reliably be assessed in semi-field and field pollinator species testing without estimating false positive or false negative? MDD’s and replicates issue

3.1 Which endpoints can reliably be assessed in semi-field and field pollinator species testing without estimating false positive or false negative? MDD’s and replicates issue

Co-dependency between a specialist Andrena bee and its death camas host, Toxicoscordion paniculatum

Among associations of plants and their pollinating bees, mutually specialized pairings are rare. Typically, either pollen specialist (oligolectic) bees are joined by polylectic bees in a flowering species’ pollinator guild, or specialized flowers are pollinated by one or more polylectic bees. The bee Andrena astragali is a narrow oligolege, collecting pollen solely from two nearly identical species of death camas (Toxicoscordion, formerly Zigadenus). Neurotoxic alkaloids of these plants are implicated in sheep and honey bee poisoning. In this study, T. paniculatum, T. venenosum and co-flowering forbs were sampled for bees at 15 sites along a 900-km-long east–west transect across the northern Great Basin plus an altitudinal gradient in northern Utah’s Bear River Range. Only A. astragali bees were regularly seen visiting flowering panicles of these Toxicoscordion. In turn, this bee was never among the 170 bee species caught at 17 species of other prevalent co-occurring wildflowers in the same five state region (38,000 plants surveyed). Our field pollination experiments show that T. paniculatum is primarily an outcrosser dependent on pollinator visitation for most capsule and seed set. Thus, both A. astragali and two sister species of Toxicoscordion are narrowly specialized and co-dependent on each other for reproduction, illustrating a rare case of obligate mutual specialization in bee–plant interactions.

Novel microsatellite loci reveal high genetic diversity yet low population structure for alfalfa leafcutting bees in North America

The alfalfa leafcutting bee, Megachile rotundata (ALCB) is an economically important pollinator necessary for seed production of the critical forage crop alfalfa, Medicago sativa. The pollinator was accidentally introduced to North America from Europe approximately 70 years ago, and it is primarily produced in Canada and shipped to the United States annually en masse for seed field pollination. We investigate how the large-scale commercial movement of this bee affects the genetic structure of populations in the North American seed growing system and compare the genetic diversity and structure of introduced North American bees with two native European populations. Using 16 newly developed microsatellite loci, we describe the North American population structure of this bee. ALCBs collected from alfalfa seed farms have a degree of genetic variability similar to one native European population, but lower than the second. Considering that the species was accidentally introduced into North America, we anticipated more signature of a founder effect. Despite the level of genetic variability, we found little, if any, genetic structuring across North America, other than that the North American populations were distinct from the European populations sampled. While we detected some sub-structure in North American populations using Bayesian methods, the structuring was without geographic pattern, and we propose it is the result of the intense human management and movement of these bees. The trade and movement of these bees by humans has created a nearly panmictic M. rotundata population across the continent, which has implications relevant to the preservation and conservation of other bee pollinators.

Performance of hymenopteran insects as pollinators of pumpkin in Meghalaya

Pumpkin is a major cultivated crop particularly in north eastern states of India that depends on insects for the pollination, as the pollens of these plants are large sized and sticky. In the present study, field and lab experiments were conducted to determine the efficiency of the pollinators of pumpkin based on their diversity, relativeabundance and foraging activity. Total four hymenopteran insect pollinators were observed in field viz., bumble bee, little honey bee, Indian honey bee and Digger bee. On the basis of abundance and relative abundance bumble bee was identified as most abundant pollinator of pumpkin with 69.69 per cent mean relative abundance as other pollinators mean relative abundance was less than 25 per cent and it was only 3.49 per cent for Indian honey bee. Foraging speed and foraging rate of bumble bee was 7.13 sec/flower and foraging rate was 3.80 flower/minute. To ensure the efficient pollinator of pumpkin flower, pollen carrying capacity, pollen deposition and percent deposition of viable pollen was studied for all the pollinators in field and laboratory condition. The pollen carrying capacity of pollinators ranged from more than 7 mg to 1 mg. It was highest for bumble bee which was 7.33 mg followed by little honey bee (6.66 mg) and least pollen carrying capacity was observed in Digger bee (1.67 mg). Pollen depositions by pollinators on stigma in a single visit was again highest for bumble bee (565 pollen grains) with maximum number of viable pollen deposition 224.33 pollen grains out of which 39.7 per cent pollen was viable. So on the basis of above result it can be concluded that bumble bee was the most abundant and most efficient pollinator of pumpkin.

Pollinator Limitation and Crop Production: Experimental Observations on Few Economically Important Vegetable Crops in West Bengal, India

Pollination limitation and its impact on agricultural production is a serious concern of recent time. Assessment of the extent of dependency of various pollinator dependent crops on insect pollination assumes importance in this context. On the other hand, measures for restoring the pollination service needs to be explored for sustainable production of economically important crops particularly for the benefit of the small and marginal farmers. The present study aimed to assess the extent of insect pollinator dependency of brinjal (eggplant) fruit production and impact of honey bee (Apis cerana F) box introduction on the production in vegetable farms of North 24 Parganas, West Bengal, India. Through a pollinator exclusion experiment using enclosures it was found that brinjal fruit production reduces by 54.5 % when they are pollinator limited. This finding is in contrast with earlier report of 25 % dependency. The flower density in a pollinator limited environment was observed to increase by 31 %. This might be plant’s response to pollinator limitation where the plant invests more on reproductive structure than vegetative structures. However, this requires further exploration. Introduction of bee boxes in brinjal, pumpkin and pointed gourd farms showed significant increase in fruit production. This indicates both pollination limitation as well as the need for increasing the pollinators in the crop field for sustainable crop production.

Comparison of Pollinating Activities on Cherry Flower by Honeybee (Apis mellifera), Bumblebee (Bombus terrestris) and Hornfaced Bee (Osmia cornifrons)

체리농가에서 체리의 인공 수분을 대체하고 더불어 이상 기상환경 하에서 자연수분을 약점을 보완하고자 양봉꿀벌 등 3종의 화분매개곤충을 투입하여 체리의 화분매개활동 특성과 착과율 및 상품성, 경제적 수익률 등을 분석하였다. 투입된 화분매개곤충별 소문 출입활동은 양봉꿀벌의 경우 9시에 활동정점을 보인 후 11시부터 17시까지 꾸준한 활동을 보였으며, 서양뒤영벌의 경우 9시부터 17시까지 출입활동에 큰 차이 없었고, 머리뿔가위벌의 경우 11시에서 13시까지 활동정점을 보인 후 감소추세를 보였다. 봉종별 화분매개활동은 꿀벌과 서양뒤영벌의 경우 9시부터 11시까지 매개활동이 왕성하나 그 이후 낮아지는 경향을 보였으며, 머리뿔가위벌의 경우 13시에서 15시 사이에 정점을 보인 후 감소하는 경향을 보였다. 착과율 조사에서 양봉꿀벌 16.1%, 서양뒤영벌 12.7%, 머리뿔가위벌 6.5%로 나타났으며 전체적으로 착과율은 20% 미만으로 매우 낮은 경향을 보였으며 이 결과는 발아기 저온현상과 결실기의 이상 고온으로 인한 결실불량에 의한 착과율의 심각한 감소를 초래한 것으로 판단된다. 시험곤충별 화분매개활동에 의한 체리의 생산물 품질에서 과중은 양봉꿀벌과 서양뒤영벌, 머리뿔가위벌 방사구가 각각 5.9g, 5.7g, 5.6g으로 서로 비슷한 경향이었으며 자연수분구 3.8g보다 무겁게 나타났다. 당도는 각 시험곤충별로 차이가 있었는데 양봉꿀벌과 서양뒤영벌 방사구에서 각각 21.9 Brix(%), 20.9 Brix(%)로서 머리뿔가위벌과 자연수분구 보다 높아 상품성이 매우 높은 것으로 나타났으며, 체리의 화분매개곤충 종별 경제성 조사에서 양봉꿀벌 방사구가 순수익이 10,434천원/990㎡으로 자연수분구의 순수익 8,820천원/990㎡ 대비 118%의 이익이 생겼고, 서양뒤영벌 방사구는 9,865천원/990㎡으로 자연수분구 대비 112%의 이익이 더 발생하였다. 머리뿔가위벌 방사구는 순수익이 8,878천원/990㎡으로 자연수분구 대비 순수익 증가분이 거의 없어 경제적으로 체리의 화분매개곤충으로서 적합도가 낮은 것으로 조사되었다.

Farmers Perception on Effect of Pesticide on Insect Pollinators at Padampur and Jutpani Vdcs, Chitwan, Nepal

A survey was conducted to know the farmers perception on the effect of chemical pesticide on insect pollinators at Jutpani andPadampur VDCs, Chitwan, Nepal in 2013. Thirty households were randomly selected and semi-structured questionnaire was used to collect necessary information by face-to-face interview. Majority of the farmers (60%)applied pesticides on crops during mid day. Half of the farmers (50.00%) rankedpopulation decline as effect of pesticide on pollinators, some farmers (16.67%) also observed dead pollinators in field and hives, affecting their distribution (13.33%) and repelling them from field as mentioned by the respondents (13.33%). Majority of respondents (56.67%) perceived that misuse and overuse of chemical pesticide was the major cause of declining insect pollinators, among other causes, 16.67% farmers replied deforestation, 10.00% environmental pollution and 6.67% less cultivated area responsible for the decline. Very few farmers (6.67%) could realise the incidence of disease on pollinator due to pesticidal effects. Int J Appl Sci Biotechnol, Vol 4(1): 64-66

Reproductive biology and pollen–pistil interactions in Passiflora species with ornamental potential

The objective of this work was to study the reproductive systems, pollen viability, and pollen–pistil interactions in 11 species of Passiflora. The reproductive systems were evaluated by the pollen/ovule ratio (P/O) and field pollination. Pollen viability was estimated by in-vitro germination of pollen grains and the colourimetric method with 2,3,5-triphenyltetrazolium chloride (TTC) and the pollen–pistil interactions through aniline blue fluorescence. According to the P/O ratio, Passiflora suberosa, Passiflora morifolia, Passiflora capsularis, and Passiflora tenuifila were classified as obligatory autogamous, Passiflora foetida was classified as facultative autogamous, and the other species as facultative allogamous. Controlled pollination under field conditions identified six self-incompatible (Passiflora edulis f. flavicarpa, Passiflora gibertii, Passiflora muchronata, Passiflora galbana, Passiflora racemosa, and Passiflora edmundoi) and five self-compatible (P. tenuifila, P. morifolia, P. capsularis, P. foetida, and P. suberosa) species. Interspecific hybridisations were successful for some combinations, and the fruits obtained produced fertile seeds. Regarding pollen viability, there were different responses among species. P. capsularis showed the highest in-vitro germination (80.1%) and stained pollen grains (96.2%). In self-incompatible species, the pollen–pistil interactions showed pollen tube inhibition due to the irregular deposition of callose, while, in self-compatible species, regular deposits of callose were observed. The results obtained from studies of the reproductive biology can aid in planning crosses and establishment of Passiflora breeding programs using compatible genotypes with expressive ornamental potential.

A simple pollen collection, dehydration, and long-term storage method for litchi (Litchi chinensis Sonn.)

A simple method for pollen collection and storage was devised for three litchi cultivars, namely, ‘Sanyuehong,’ ‘Shuidong,’ and ‘Guiwei’. This method could realize long-term pollen storage over periods of up to two years for artificial pollination and crossbreeding. The most suitable drying method for litchi pollen was the use of an air-blowing electric dryer at 35°C for 6h. The germination rate of pollen stored at different temperatures (30°C, 25°C, 15°C, 4°C, and −86°C) was investigated. The pollen germination rate decreased to lower than 5% after 9, 16, 27, and 52d at 30°C, 25°C, 15°C, and 4°C, respectively. A significant negative correlation was observed between pollen germination rate and storage time. For all litchi cultivars tested, pollen cryo-stored (−86°C) for one year showed significantly higher germination rates than those stored under the other conditions. Pollen stored at −86°C maintained a high germination rate of above 70% even after two years of storage. Thus, our results indicated that storage of pollen at 4°C was suitable for field pollinations in the blooming season for up to two months. However, storage at −86°C maintained the high germination rates required for artificial hybridization even in the second year of storage.