Pollination Treatments Research Articles

Decay of self-incompatibility within a lifespan in Physalis acutifolia (Solanaceae)

Key messageSelf-incompatibility decays with age in plants of Physalis acutifolia, and plants that have transitioned to selfing produce fewer seeds but with comparable viability. Self-compatibility in this system is closely related to flower size, which is in turn dependent on the direction of the cross, suggesting parental effects on both morphology and compatibility.The sharpleaf groundcherry, Physalis acutifolia, is polymorphic for self-compatibility, with naturally occurring self-incompatible (SI) and self-compatible (SC) populations. Moreover, SI individuals have been documented to transition to SC with age, at least in greenhouse conditions. Here we tested whether this within-lifespan transition occurs predictably (developmental decay of SI) or could result from a lack of pollination (a plastic response). Using greenhouse crosses, we demonstrated that SI P. acutifolia plants transition to SC after 70 days, regardless of pollination treatment, consistent with predictable developmental decay. This loss of SI corresponds to a loss of pollen inhibition, with self-pollen often reaching the ovary after 24 h. The originally SI plants that transition to SC can produce viable seeds from self crosses, albeit significantly fewer than from outcrosses of SI plants or from lines fixed for SC. Throughout the experiment, we observed that flower size, which differs between SI and SC populations, was highly correlated with the compatibility phenotype. These findings suggest that the mechanisms leading to the loss of SI during a lifespan are similar to those involved in fixed losses of SI, but that older plants that transition to SC do not present the same reproductive capacity as fixed selfers.

Managed honeybees and soil nitrogen availability interactively modulate sunflower production in intensive agricultural landscapes of China.

Insects provide important pollination services for cops. While land use intensification has resulted in steep declines of wild pollinator diversity across agricultural landscapes, releasing managed honeybees has been proposed as a countermeasure. However, it remains uncertain whether managed honeybees can close the pollination gap of sunflower (Helianthus annuus L. [Asterales: Asteraceae]) in areas lacking wild pollinators, and how the benefits of honeybees to sunflower production are modulated by soil nutrients. We investigated the effects of 3 pollination treatments (open, self and hand pollination) on sunflower yield parameters. We also estimated the pollination efficiency of managed honeybees (Apis mellifera L. [Hymenoptera: Apidae]), and analyzed the effects of honeybee visitation and soil nitrogen on sunflower yield parameters. Insect pollinators contributed 73% of seed set and 69% of the weight of filled seeds per head in the open pollination of sunflowers, but large pollination deficits still existed. Insect pollination may enhance sunflower yield by augmenting the number and weight of filled seeds per head, but not by altering the total number of seeds. Except for the total number of seeds per head, yield parameters increased significantly with the number of honeybee visits. Low nitrogen accelerated the positive effect of honeybee pollination on sunflowers, and alleviated the negative effect of distance of beehives on honeybee visitation rate. We conclude that managed honeybees could be used to pollinate sunflowers in areas with the shortage of wild pollinators, and sunflower production may benefit from shortening the distance of beehives and lowing of nitrogen fertilizer inputs.

How multi-species pollination boosts strawberry yield, quality, and nutritional value

A diverse assemblage of insect visitors can provide functional complementarity within plant pollination due to differences in characteristics such as their physical traits, visitation rate and foraging time of day or year. In a horticultural context, greater functional complementarity may play a crucial role in enhancing fruit yield and quality by improving pollination. We tested whether the identity of the crop pollinators (bumblebee Bombus terrestris and hoverfly Eupeodes corollae) independently and additively influenced commercial strawberry yield, quality, and nutritional parameters such as vitamin C and sugar concentration. Fragaria x ananassa “Malling Champion” plants received pollination treatments of either a) “control”: self-pollination where pollinators were excluded, b) “bee”: bumblebee Bombus terrestris, c) “hoverfly”: Eupeodes corollae, d) “combined”: both B. terrestris and E. corollae. Hoverflies and bumblebees exhibited distinct visitation patterns throughout the day, establishing a functional complementary relationship that enhances pollination success and crop output as well as vitamin C concentrations. Strawberries from plants receiving pollination by bumblebees, or bumblebees and hoverflies combined, had higher yields of higher marketable quality. They also had measurably higher vitamin C content than strawberries from plants pollinated by hoverflies alone, or the control (self-pollinating) plants. This study advances our understanding of niche complementarity and its impact on fruit yield and quality. By elucidating the behavioural and temporal dynamics of pollinators, we provide valuable insights for optimizing pollination strategies in agricultural contexts. Our findings highlight the significance of behavioural factors, such as handling time and number of visits, in determining fruit quality.

The reproductive strategy of a typical distylous Ophiorrhiza alatiflora (Rubiaceae), in fragmented habitat.

Heterostyly is a genetically controlled style polymorphism, that plays an important role in promoting outcrossing and improving reproductive fitness. Although distyly is often studied in plants of the Rubiaceae family, little attention has been paid to the reproductive strategies of distylous species in fragmented habitats. Here, We report for the first time the growth of Ophiorrhiza alatiflora, a type distylous species, in karst areas and evaluate its reciprocity between long styled morph and short one. We analyze the two distyly morph differences in the ancillary polymorphic of flowers and explore their reproductive strategy in fragmented habitats. In this study, we measured the floral characteristics of different morphs and performed differential secondary metabolite analysis on different morphs and tissue organs; Different pollination treatments were carried out to observe the fruit set, pollen germination, and pollen tube elongation of O. alatiflora. Our research indicates that O. alatiflora is a typical distylous plant for the distyly has high reciprocity. Both morphs exhibit the highest fruit set of intermorph outcrossing; The pollen germination and pollen tube elongation experiments have also demonstrated that the affinity of pollen from intermorph outcrossing is highest, regardless of whether it is the long or short morph as the maternal parent; Meanwhile, O. alatiflora is an incompletely self-incompatible plant that exhibits a certain degree of self-pollination and intramorph outcrossing, which may be one of the important means to ensure sustainable reproduction in severely disturbed habitats. In the ancillary polymorphic of flowers, L-morphs flowers produce more pollen, and S-morph flowers produce more ovules to improve their male-female fitness and compensate for the asymmetry of pollen flow; Compared with S-morphs, L-morphs contain significantly higher levels of several kinds of terpenoids. S-morphs produce more flavonoids than L-morphs. The differences in secondary metabolites between L-morphs and S-morphs are mainly reflected in the different nutritional organs (including stems and leaves). Overall, our work has revealed the unique reproductive strategy of O. alatiflora in fragmented habitats based on the characteristics of distyly, verifying the hypothesis that the distyly of O. alatiflora promotes outcrossing and avoids male-female interference, improving male-female fitness and this is the first time in the Ophiorrhiza genus.

Reproductive Biology in the Possible Last Healthy Population of Parodia rechensis (Cactaceae): Perspectives to Avoid Its Extinction.

All 32 Brazilian species of Parodia Speg (Cactaceae) occurring in Rio Grande do Sul State are considered threatened, according to the IUCN criteria. Until 2021, Parodia rechensis (CR) was known by only two small populations. However, a new population with over 400 individuals was discovered in 2021, prompting the study of its reproductive biology as a way to promote its conservation. Anthesis, breeding system, and natural pollination were studied in the field. The breeding system was studied by applying controlled pollination treatments to plants excluded from pollinators (bagged). Germination features were studied at the Seed Bank of the Porto Alegre Botanical Garden under controlled temperatures (20, 25, and 30 °C). The anthesis is diurnal and lasts for up to four days. The flowers offer pollen as the sole resource to the pollinators. The study species is unable to set fruit and seed without the agency of pollinators and has self-incompatible (unable to set fruit and seeds when pollinated with pollen of the same individual) characteristics that can considerably restrict its reproduction. Native bees of Halictidae and Apidae (Hymenoptera) are the main pollinators, with a smaller contribution of Melyridae (Coleoptera) and Syrphidae (Diptera). Natural fruit set is moderate (≤64%, per individual), but the species presents vegetative growth, producing several branches from the mother plant. Seeds showed the optimum germination rate at 20 °C and an inhibition of 75% in germinability at 30 °C. Our findings suggest the need to manage the species' habitat to guarantee the permanency of the plants and healthy populations of pollinators as well. Our findings raise concerns about the germination and establishment of new individuals in the context of rising temperatures caused by climate change. Suggestions for the possible management of the extant populations are made.

Significance of honeybee pollination in increasing seed yield of Trifolium alexandrinum (Fabales: Fabaceae) and its impact on economic sustainability of smallholder farmers.

A major limitation to producing high seed yields in berseem clover (Trifolium alexandrinum L.) is failure to set seed, predominantly due to lack of pollination. Despite the importance of berseem clover as a leading forage legume, the contribution of pollinators to seed set is scarce. In Pakistan, the honeybee population is declining mainly because of the extensive use of neonicotinoid pesticides and habitat fragmentation. This, combined with the region's harsh environment and the use of inferior, locally bred genotypes, has resulted in low seed yields. Insufficient seed availability leads to limited forage supply, resulting in poor livestock nutrition, which subsequently impacts livestock health and productivity, and reduces farmers' income. The present study estimated the seed production of 3 berseem clover genotypes resulting from honeybees [Apis mellifera L. (Hymenoptera: Apidae)] pollination in 2 growing seasons (2012-2014) in the central Punjab region of Pakistan. Experiments had 2 pollination treatments (open pollination and honeybee inclusion) and 3 seed genotypes, viz. farmer own-saved, market, and the improved variety cultivars. For both growing seasons, honeybee pollination resulted in significant increases in seed yields ranging from 35% to 67%, regardless of seed genotype. With the exception of the number of seed heads/m2, all seed yield parameters also increased significantly in response to honeybee inclusion. The combination of improved variety and honeybee inclusion resulted in the production of a maximum number of seeds per head (45.3), 1,000-seed weight (3.7 g), and estimated seed yield (375.5 kg/ha). In addition, the increase in estimated net income of seed ranged from PKR 82,485 Rs/ha (US$844/ha) to PKR 168,975 Rs/ha (US$1728/ha) with the use of honeybees as an insect pollinator across all the seed genotypes. Honeybee pollination has broader implications for mixed farming systems by playing a key role in preserving biodiversity and promoting sustainable agriculture. It also enhances the quality and quantity of berseem crops by increasing the production of high-quality seeds and forage leading to improved livestock productivity and family food security which strengthens the economic resilience of rural communities.

Rock Melon Crop Yield Prediction using Supervised Classification Machine Learning on Cloud Computing

Precision agriculture is a technology-driven approach to farmer to improve their crop yields and reduce costs. One of the major challenges facing farmers today is the lack of precise prediction which leads to decreased production and mismanagement of labour and resource. Precision technology is costly, and they only rely on manual observations which are less precise. Crop yield prediction systems on cloud computing can solve both problems by predicting the harvested fruit at earlier stages of farming and ease farmers to make decisions. In this study, we proposed a crop yield prediction system for farmers that utilizes cloud computing and machine learning techniques. The system uses data on the physical growth of the plant such as plant’s height at 15 and 30 days after transplant, type of pollination treatment, condition of the leaves, and their variety to predict the crop yield at the early stage. Logistic regression, k-nearest neighbour, and random forest classifier were used to compare the accuracy of the model. Our result shows that by using a random forest classifier, it can achieve an accuracy of 91% which is higher than logistic regression which is only 73% of accuracy, and k-nearest neighbour with 82% accuracy. The study highlights the potential of precision agriculture, cloud computing, and machine learning to revolutionize the way farmers manage their crops and increase their efficiency and productivity, even with the limited resources and hardware that many farmers have.

Animal pollination shapes fruits market features, seeds functional traits and modulates their chemistry

In this study, we experimentally addressed the impact of different pollination treatments on the morphological, reproductive and chemical traits of fruits and seeds of two crop species, the wild strawberry (Fragaria vesca L.) and cowpea (Vigna unguiculata (L.) Walp.). Multiple flowers from each plant were exposed to different pollination treatments: (1) self pollination, (2) hand cross pollination and (3) open pollination. Both crops were positively affected by open pollination in terms of morpho-chemical parameters concerning the marketability (e.g., 35% decrease in sugar/acid ratio in open pollinated strawberries compared to the autogamous ones) and the seed germination rate as a proxy of reproduction efficiency (e.g., the almost complete absence of seed abortion in the open pollination treatment). Remarkably, the pollination treatment also strongly influenced the phytochemical composition. Open-pollinated strawberries exhibited a higher relative concentration of compounds endowed with nutraceutical properties such as anthocyanins, ellagic acid derivatives and flavonoids. At the same time, cowpea seeds displayed higher concentrations of anti-nutrients in the self pollination treatments, such as saponins, compared to the open and hand cross pollinated seeds. This study suggests the presence of a link between the pollination mechanism, market quality, plant reproduction and chemical properties of fruits and seeds, supporting the intricate interplay between pollinators, plants and human nutrition, highlighting the crucial importance of animal pollination in the ecological and dietary contexts.

Nocturnal pollinators significantly contribute to tree bean (Parkia timoriana (DC.) Merr.) reproductive success compared to diurnal pollinators

Nocturnal pollinators significantly contribute to tree bean (Parkia timoriana (DC.) Merr.) reproductive success compared to diurnal pollinators

Pollen source affects acorn production in pedunculate oak (Quercus robur L.)

Acorn production in oaks (Quercus spp.) shows considerable inter-annual variation, known as masting. The effects of pollen sourced from trees within or outside the stand on acorn production were investigated in pedunculate oak (Quercus robur L.) in an ancient mixed woodland during two moderate masting years. Comparisons were made between natural pollination, hand pollinations with out-of-stand pollen, in-stand pollen or a 1:1 combination of the two pollen sources, and for bagged flowers left unpollinated. After all treatments, > 85% of the flowers or developing acorns were aborted between May and August of both years. When flowers were protected with pollen bags and no pollen added, no acorns were produced. In contrast, hand pollination with out-of-stand pollen produced the most acorns both years and significantly more than within-stand pollen or natural pollination in 2022. Hand pollination with out-of-stand or within-stand pollen provided significantly more acorns than natural pollination in 2023. In 2022, hand pollination with a 1:1 mixture of out-of-stand and within-stand pollen yielded an intermediate number of mature acorns between those for the out-of-stand and within-stand pollination treatments. The study provides clear evidence of maternal choice during acorn development in pedunculate oak and of the benefits of pollen supplementation. It also confirms that pedunculate oak is a fruit-maturation masting species; abortion of pollinated flowers and immature acorns determines a mast year (rather than the number of flowers produced) at this site.

Honeybee (Apis mellifera L.) pollination enhances the yield and flavor quality of kiwifruit.

Pollination is essential for achieving high yields and enhancing the quality of kiwifruit cultivation, both of which significantly influence growers' interests and consumers' preferences. However, compared to studies on yield, there are fewer studies exploring the impact of pollination methods on the flavor of kiwifruit Actinidia chinensis Planchon. This study examined the effects of bee (Apis mellifera L.) pollination and artificial pollination on the yield and flavor of kiwifruit in the main producing areas of China. Compared with those pollinated artificially, bee-pollinated kiwifruit exhibited a greater fruit set rate, heavier fruit weight, and greater number of seeds. Notably, the number of seeds was positively correlated with fruit weight in bee-pollinated kiwifruit, whereas no such correlation was detected in artificially pollinated fruit. Bee pollination not only enhanced the yield but also improved the flavor of kiwifruit. Specifically, bee-pollinated kiwifruit contained higher levels of sucrose and lower concentrations of glucose and fructose, while the acid content was less affected by pollination methods. Furthermore, significant differences were observed in the volatile organic compound (VOC) levels in kiwifruit subjected to different pollination treatments, with bee-pollinated fruit exhibiting a superior flavor. Our findings provide new insights into the beneficial role of bee pollination in enhancing kiwifruit yield and quality, underscoring the crucial importance of bees in kiwifruit pollination.

Arbosana Olive Is Self-Incompatible, but Inter-Compatible with Some Other Low-Vigor Olive Cultivars

Trendy high-density olive fields are often monovarietal orchards, mostly using the cultivar Arbequina. However, Arbequina shows a strong self-incompatibility response, and its yields depend on wind cross-pollination, which is not always available. With the aim of finding suitable self-compatible cultivars that can replace Arbequina, we evaluated pollen–pistil interaction, fruit set and seed paternity in Arbosana under different pollination treatments: self-pollination, open-pollination and three cross-pollination treatments: × Arbequina, × Sikitita and × Koroneiki. All these cultivars are low-vigor cultivars suitable for high-density orchards, making them potential pollinizers for Arbosana. The results show that Arbosana is also self-incompatible with a strong reduction in fruit set due to a lower fertilization level caused by a strong inhibition of pollen tube growth in self-pollinated flowers. Seed-paternity analyses confirmed the self-incompatibility response of Arbosana and suggest that some fruit obtained in bagged shoots under self-pollination were, in fact, a product of cross-fertilization. In conclusion, we recommend against the use of Arbosana in large monovarietal orchards. On the contrary, good results were obtained under cross-pollination with Sikitita, Arbequina and Koroneiki pollen, allowing us to recommend them as pollinizers for Arbosana in appropriate pollination designs. This is the first time Arbosana self-incompatibility has been reported.

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.

Self-Incompatibility in Devil's Potato (Echites umbellatus Jacq., Apocynaceae) May Explain Why Few Flowers Set Fruit.

Pollinators are needed for the reproduction of Echites umbellatus, and only sphingid moths have mouthparts long enough to reach the nectar at the bottom of the species' long, twisted floral tube. Though plants produce many flowers over a period of several months, one observes very few fruits in nature. We asked: (1) Are plants self-compatible, or do they need pollen from another individual to set fruit and seed? (2) Are cross-pollinations between unrelated individuals more successful than crosses with relatives? (3) How does the relatedness of pollen and ovule parent plants affect fruit set, seed number, and seed quality? We investigated the breeding system of E. umbellatus by collecting fruits from seven sites, growing plants and performing hand pollinations over a period of several years, collecting and measuring fruits and counting seeds. Echites umbellatus is self-incompatible, though some individuals produce fruit by self-pollination. Cross-pollinations between unrelated individuals set the most fruit (59%), and those that were self-pollinated set the least (9%). Fruit set from cross-pollinations between related individuals was intermediate (32%). Although the number of seeds per fruit did not differ significantly among pollination treatments, fruits from self-pollinations had substantially fewer viable seeds than outcrossed fruits, with fruits from sibling crosses being intermediate. There were higher levels of self-compatibility in the fragment populations compared with plants from intact habitats. Self-incompatibility may explain why fruit set is low in this plant species; future investigation into the breakdown of self-incompatibility in smaller populations is warranted.

Pollination and pollen plant diversity by Apis cerana cerana during olive flowering based on DNA metabarcoding

AbstractTo understand the role of Apis cerana cerana in olive tree (Olea europaea L.) pollination, pollinators and pollen carried by bees were collected from 11 experimental plots during the flowering period. The abundance and diversity of pollen plant species were investigated using DNA metabarcoding. A total of 583 pollinators were collected and A. cerana cerana accounts for 46.83%. Further analysis revealed a total of 56 families, 136 genera and 195 plant species in bee pollens. O. europaea is the dominant species accounting for 42.02 ± 34.89% and then followed by Sedum japonicum (8.70 ± 16.42%). Diversity index showed that the abundance and diversity of pollen plant species were the highest in Wanzhou (WZ) and lowest in Hechuan (HC). This suggests that Wanzhou sample plot has a greater abundance of plant species to supplement the bee diet. Excessive presence of miscellaneous flowering plants in olive plantations can distract bees from collecting olive tree pollens. Therefore, their abundances can be reduced appropriately while ensuring food diversity for the bees. Based on the abundance of plants in pollens, we recommend that appropriately planting of S. japonicum, Youngia japonica and Vicia villosa in olive plantations with fewer flowering plants could be an effective supplement of bee food. Our results not only contribute to future studies on olive tree pollination but also provide new ideas for enriching flowering plants in or around olive plantations.

Analyses of the sexual reproductive traits for conservation and sustainable utilization of Dactylorhiza hatagirea – A critically endangered medicinal orchid of North-western Himalaya

Analyses of the sexual reproductive traits for conservation and sustainable utilization of Dactylorhiza hatagirea – A critically endangered medicinal orchid of North-western Himalaya

Beekeeping improves shea pollination and fruit set in West African agroforestry parklands

Abstract Shea (Vitellaria paradoxa C.F. Gaertn) is a fruit tree of domestic and industrial importance in arid and semi‐arid regions of Sub‐Saharan Africa. Fruit set is largely dependent on insect pollination but recent studies have revealed a pollen deficit. The introduction of managed bees into orchards is an effective approach for enhanced pollination services in temperate climates. However, there is limited information to guide the adoption of this practice in agroforestry parklands. This study investigated the effect of managed honey bee colonies (Apis mellifera) on fruit yield of shea in six parklands across three regions of Ghana. Tree proximity to the apiary had a detectable effect on fruit set within a 500 m range of the apiary. Proximity of shea trees to apiary was significantly related to number of immature fruit set but not number of mature fruits. Fruit weight and size were not significantly related to distance from apiary or pollination treatment. This implies that the introduction of beekeeping has the potential to address shea pollination deficit at least within a 500 m range of the apiary. Further studies are needed to determine the optimal hive density per acreage of shea parkland to maximise pollination services.

Pollination ecology of Ranzania japonica (Berberidaceae), a perennial plant of a monotypic genus endemic to deep‐snow regions in Japan

AbstractPlants that bloom in early spring often face constraints on reproduction, which are influenced by low temperatures and unpredictable weather conditions that affect pollinator activity. We aimed to elucidate the pollination ecology and the mating system of Ranzania japonica (Berberidaceae), a perennial plant of a monotypic genus endemic to deep‐snow regions in Japan. We documented the flowering phenology and visiting insects in the field, and conducted pollination experiments by using artificial treatments. R. japonica was suggested to be self‐incompatible but not pollen‐limited. Fruit set varied between years, and florivory seemed to have a negative influence on fruit set. Insects from various taxa were observed to visit the flowers of R. japonica, with Eusphalerum sp. (rove beetle) being the most abundant, followed by Bombylius major and hymenopteran species. The stamen movement in response to insect visits was observed. The results of the observation and the pollination treatments suggested that small‐ and medium‐sized Hymenoptera were the main pollinators and rove beetles may also contribute to pollination in R. japonica. Because early spring weather can be unsuitable for activity of bees, rove beetles may act as supplementary pollinators of R. japonica. The role of the supplementary pollinators may be an overlooked but important aspect for understanding the pollination biology of early‐spring blooming plants.

The patterns of inbreeding depression in food-deceptive Dactylorhiza orchids.

Inbreeding depression (ID) in food-deceptive plants have been reported previously, however, it has not been often proven that selfed seeds germinate better than outbred ones or that selfing affects ID. To resolved these issues, food-deceptive related Dactylorhiza majalis, D. incarnata var. incarnata and D. fuchsii orchids were investigated. Hand pollination treatments and control pollination were conducted. Fruit set, number of seeds per fruit, seed length, number of well-developed seeds per fruit, and proportion of in vitro asymbiotic germination seeds, were analyzed in relation to inflorescence levels and used as fitness indicators for these orchids. The ID and pollen limitation were measured. The lowest ID (δ = -1.000) was in D. majalis, and present in combination with a high pollen limitation in its populations. D. fuchsii showed higher ID (δ = 0.366), and D. incarnata var. incarnata weak ID (δ = 0.065), although ID varied between its fitness components. The seed number per fruit differed significantly between the treatments and the inflorescence levels in treatments. This study emphasizes that the breeding system rather than the flower position on the inflorescence shaped the quality and quantity of reproductive output. The ID and its effect on germination of food-deceptive orchid seeds undoubtedly played an important role.

Exploring sterile pollen technique as a novel tool for management of Palmer amaranth (Amaranthus palmeri)

AbstractThe success of the insect sterile technique (IST) in managing insect pests raised the hypothesis that a similar approach could be employed to control weed populations. Here, we investigated the feasibility of employing irradiated sterile pollen as a means to disrupt seed production in dioecious weeds, specifically focusing on Palmer amaranth (Amaranthus palmeri S. Watson). Our goal was to determine the optimal irradiation dose that strikes a balance between inducing sterility and preserving competitiveness, as excessive doses could result in pollen mortality, while low doses may retain fertility. Plants were grown in a greenhouse during the summer of 2020 and spring of 2021. Once they reached the flowering stage, male and female individuals were isolated. Mature pollen samples were collected and exposed to varying dosages (0, 100, 200, 300, 400, and 500 Gy) of gamma rays. These irradiated and non-irradiated pollen samples were used in pollen viability assessments and hand-pollination experiments. In the hand-pollination study conducted in 2020, we employed six pollination treatments using different irradiation doses. The results showed that 300 Gy was the most effective dose, resulting in a maximum reduction of 30% in seed set compared with open pollination when irradiated pollen had prior access to the stigma through artificial pollination before open pollination. In 2021, to simulate real field conditions, three additional treatments were introduced into the study, further confirming the effectiveness of the optimal 300 Gy dose. Our findings indicate that the sterile pollen technique (SPT) using irradiated pollen can be a valuable approach for reducing weed seed production. SPT also holds potential for broad-spectrum weed control by mixing sterile pollen from multiple weed species in a single application. Additionally, it could aid in managing herbicide-resistant weeds that have survived in-season control efforts. This research contributes to the development of novel and sustainable weed management strategies.