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Premise: Heterospecific pollen transfer, the transfer of pollen between species, is common among co‐flowering plants, yet the amount of pollen received is extremely variable among species. Intraspecific variation in heterospecific pollen receipt can be even greater, but we lack an understanding of its causes and fitness consequences in wild populations. Methods: We examined potential drivers of variation in heterospecific pollen receipt in Oenothera fruticosa. We evaluated the relationship between heterospecific and conspecific pollen receipt and considered how visitation by different pollinator groups, local floral neighborhood composition, and flowering phenology affect the total amount and proportion of heterospecific pollen received. Finally, we tested whether variation in heterospecific pollen receipt translated into lower seed production. Results: Heterospecific pollen was ubiquitous on O. fruticosa stigmas, but the amount received was highly variable and unrelated to conspecific pollen receipt. Heterospecific pollen receipt depended on pollinator type, the proportion of nearby conspecific flowers, and flowering date. Significant interactions revealed that the effects of pollinator type and neighborhood were not independent, further contributing to variation in heterospecific pollen. Naturally occurring levels of heterospecific pollen were sufficient to negatively impact seed set, but large amounts of conspecific pollen counteracted this detrimental effect. Conclusions: Although selection could act on floral traits that attract quality pollinators and promote synchronous flowering in O. fruticosa, the risk of heterospecific pollen is equally dependent on local floral context. This work highlights how extrinsic and intrinsic factors contribute to intraspecific variation in heterospecific pollen receipt in wild plants, with significant fitness consequences. [ABSTRACT FROM AUTHOR]

The palm Euterpe edulis is an important palm species for the extraction of palm heart, a highly profitable consumable product. Due to its importance, much research has been conducted around the ecology of this palm species. Nevertheless, information available on its reproductive ecology is quality-deficient and fragmented, resulting in misleading views of the pollination and reproductive ecology of E. edulis. Here we conduct the first thorough study assessing the relative dependence on animal pollination of E. edulis in Argentina, and conduct parallel detailed observations on floral visitors. Also, we integrate our results with those available for the species in the literature. Here we found that E. edulis has an ambophilic pollination system. However, in our study system, there was a predominance of wind pollination over insect pollination and the species can also set seeds in the absence of pollen. Also, our study shows in great detail the large diversity of insects visiting E. edulis, indicating the generalist pollination system of the species, where Hymenoptera and Diptera stand out in richness and frequency of visits. The palm represents a key resource for a wide diversity of insect visitors, but the palm does not rely on their efficiency to act as pollinators. The varied levels of reproductive dependence on animal versus wind pollination of E. edulis may be shaped by climatic and landscape conditions. Such alternative versatile strategies allow the species to guarantee the reproductive success under different ecological contexts. [ABSTRACT FROM AUTHOR]

Delayed autonomous selfing (DAS) provides reproductive assurance under conditions of pollinator and/or pollen-limitation. Few plant species have been investigated to determine if DAS is terminated when a flower is sufficiently pollinated by a pollen vector, thereby saving plant resources for other purposes. We examined this possibility in bumblebee-pollinated Salvia umbratica. We first showed that DAS resulting in high fruit set (100%) and seed set (>80%) per flower occurred in the absence of insect pollinators by means of style recurvature and was completed in 94% of flowers 72 h after they opened. In contrast, in flowers pollinated immediately after opening, DAS was prevented by corollas dropping away before styles recurve toward the upper thecae. We next showed that hand-pollination of flowers immediately after they opened resulted in high fruit set (100%) and seed set (>80%) when 5–10 pollen grains or more were deposited on their stigmas, whereas fruit set and seed set were reduced to 45.00 and 22.50%, respectively, when pollen loads were reduced to 1–3 pollen grains. Finally, we showed that on average single pollinator visits deposited 26 pollen grains on stigmas of flowers that had just opened, which is more than enough to ensure high fruit and seed set. Our results indicate that flower longevity is highly correlated with the pollinator environment and female fitness of S. umbratica , with extended flower longevity allowing DAS to occur being advantageous when pollinators are absent, while reduced floral longevity and prevention of DAS being favored when flowers are pollinated by pollinators. Thus, flower longevity in S. umbratica varies so as to optimize reproductive output and resource efforts, and is dependent on the availability and effectiveness of pollinators to pollinate flowers. [ABSTRACT FROM AUTHOR]

• The diploid chromosome number (2 n =18) in A. amygdalina has been reported for the first time from North-western Himalaya, marking a previously unrecorded finding. • Detailed analysis of meiotic behaviour, showed the occurrence of various chromosomal aberrations in three distinct populations. • The effect of various meiotic abnormalities on the frequency of chromosomal aberrations, pollen sterility, and abnormal microspore formation across the populations has been documented. • Comparison of meiotic behaviours among populations at different altitudes revealed significant differences and potential environmental influences. The limited geographic distribution of endemic species renders them more susceptible to extinction risks stemming from a myriad of factors. One such factor could be meiotic constraints, which may directly or indirectly impact the reproductive success of the endemic plant species. Thus, comprehensive research on meiotic behaviour is essential for implementing species conservation measures. This study represents the first report on the male meiotic behaviour of Artemisia amygdalina Decne., a critically endangered endemic medicinal plant species of the Kashmir Himalaya. We procured the plant material from three different locations in the Kashmir Himalaya, and the chromosome number of the species from all sites was found to be 2 n =18 (x = 9, n = 9), indicating its diploid nature. Various types of chromosomal abnormalities were found in these populations, including stickiness, univalents, out-of-plate bivalents, laggards, bridges, disturbed telophase, micronuclei, abnormal pollen grains formation and seed set formation. The overall percentage of chromosomal abnormalities varied among the populations, from 8.58 % to 25.16 %. Pollen sterility also varied among different populations, with maximum pollen sterility of 23.21 % and a minimum of 5.96 % across populations. The present findings will not only help in updating the chromosome atlas with the addition of a new report on chromosome number but also contribute to the understanding of the reproductive success of A. amygdalina. Further ecological and reproductive studies can facilitate the creation of effective management and conservation strategies for this species. [ABSTRACT FROM AUTHOR]

Bees are declining, which is worrisome since they both have intrinsic conservation value and play a major role as pollinators in both natural and managed ecosystems. Land use change and lack of suitable habitats are often suggested as driving forces of bee decline. To propose mitigation measures to halt bee decline, it is important to understand how land use relates to bee abundance and diversity, and to explore consequences for their provision of pollination services. White clover, Trifolium repens , is an outcrossing mass-flowering crop, which could serve as an abundant, although ephemeral, food resource for bees. We investigated how the bee community in 39 fields of white clover grown for seed, related to local field management (organic, conventional without insecticides and conventional with insecticides) and landscape context (proportion semi-natural land), and how this pollinator community related to white clover seed set. The honey bee, Apis mellifera , was the most commonly observed bee species, and two generalist bumble bee species, Bombus terrestris and B. lapidarius , were the subsequently most common. We observed fewer non- Apis bees, and a lower bee species richness in organic white clover seed fields compared to conventional fields independent of insecticide treatment. Bee species richness in both conventional and organic fields were positively related to the proportion of semi-natural land in the landscape, likely because of a larger species pool in such landscapes. Initial seed set in immature inflorescences was positively related to bee abundance, whereas final seed set in mature inflorescences was unrelated to bee abundance, possibly as a consequence of seed-eating weevils consuming a large proportion of the seeds. We conclude that both bee visitation and seed set in white clover benefit from conventional management and that landscapes rich in semi-natural habitats will make future crop production more resilient. The observed positive relationship between bee abundance and initial seed set suggests that if we can mitigate pest impacts and increase bee abundance in clover seed fields, the final seed yield can be increased. Thus, bee decline should be considered and mitigated both to maintain biodiversity in general and for crop seed production specifically. • Lower (non-Apis) bee abundance and species richness in organic white clover fields • Bee species richness positively related to the proportion of semi-natural land • Initial seed set in immature inflorescences positively related to bee abundance • Final seed set was unrelated to bee abundance, possibly due to seed-eating weevils [ABSTRACT FROM AUTHOR]

This report describes the methods and results from the second season (2013 – 2014) of Lupinus nipomensis seed bulking at the CCBER Greenhouse and Nursery facility

Abstract Background Small populations are predominantly vulnerable to inbreeding and inbreeding depression (ID). Owing to increased levels of inbreeding on individuals in small populations, ID could decrease the population growth rate, as well as its effective size, and exacerbate the extinction risk. Inbreeding depression remains a crucial area of research in conservation biology, ecology, and evolutionary biology. This study aims to elucidate the reproductive biology, inbreeding, and ID of Paeonia decomposita and to conserve, manage, and improve them better in the future. Results Paeonia decomposita belongs to a xenogamous category and is partially self-compatible; moreover, it requires pollinators for seed production. Lately, the occurrence of pollination and pollinator limitations has affected the seed set. Low seed set primarily correlated with an abnormality of meiosis in the pollen mother cell, moderate to low genetic diversity, drought and extreme weather, pollinator limitation, or carpel space limit. One of the primary reasons for endangered mechanism in P. decomposita is the low seed set under natural conditions. The cumulative value of ID was positive, and outcrossed progeny outperformed selfed progeny. Conclusions Paeonia decomposita requires pollinators to ensure seed production either through autogamy, geitonogamy, or allogamy. It is both allogamous and partially self-compatible, as well as a successful outcrosser. Inbreeding occurs frequently and results in ID, which imposes a potential threat to the survival of populations. Besides, it needs conservation via in situ and natural return methods.

Abstract Greater pollination intensity can enhance maternal plant fitness by increasing seed set and seed quality as a result of more intense pollen competition or enhanced genetic sampling. We tested experimentally these effects by varying the pollen load from a single pollen donor on stigmas of female flowers of Dalechampia scandens (Euphorbiaceae) and measuring the effects on seed number and seed mass. Seed set increased rapidly with pollen number at low to moderate pollen loads, and a maximum set of three seeds occurred with a mean pollen load of 19 pollen grains. We did not detect a trade‐off between the number of seeds and seed mass within a fruit. Seed mass increased with increasing pollen load, supporting the hypothesis of enhanced seed quality via increased pollen‐competition intensity or genetic sampling. These results suggest that maternal fitness increases with larger pollen loads, even when the fertilization success is already high. Our results further highlight the importance of high rates of pollen arrival onto stigmas, as mediated by reliable pollinators. Comparing the pollen‐to‐seed response curve obtained in this experiment with those observed in natural populations suggests that pollen limitation may be more severe in natural populations than predicted from greenhouse studies. These results also indicate that declines in pollinator abundance may decrease plant fitness through lowered seed quality before an effect on seed set is detected.

The base - population of the controlled cross breeding is one of the important factors to develop a new improved cultivar. Since the incompatible nature of sweet potato remains a barrier for genetic improvement, therefore it requires a lot of crossed pairs. This study aimed to determine the level of incompatibility among crossing line between high yielding and micronutrient content cultivars. The field experiment conducted at Brawijaya University Research Station, Jatikerto-Malang, during February to August 2015. The North Carolina Design II was applied to sixty pairs controlled cross breeding and their sixty reciprocal pairs of six cultivars for micronutrient content enrichment with ten high yielding cultivars. The observations were made to the cross flowers number, capsules, fruit sets, and seeds number. The level of incompatibility between crossed pairs was determined by the level of fruit set. The result showed that most pairs were compatible (fruit set > 20%) and only few were incompatible (fruit set < 10%). Among six parents with micronutrient content enrichment, two of them, have a high compatibility as as female parents, to all the high yielding cultivars, i.e. BIS OP-61 and Cangkuang. Positioning as a female parent can improve the effectiveness of its selection scheme.

In red clover seed production, low seed yield is limiting the commercial exploitation of tetraploid red clover. To explore if pollination is the limiting factor for the seed yield in tetraploid red clover, we investigated pollinator behaviour and plant reproductive success in diploid (2x) cultivar 'Rajah' and tetraploid (4x) cultivar 'Amos' using honey bee and hand pollination approaches. We measured the seed set at the flower head level with the increasing visitation rate of honey bees (one bee, two bees and open pollination) and pollen diversity (one and two pollen donors) of hand pollination. We found no difference in honey bee pollination behaviour (visitation rate) between the diploid and tetraploid red clover. Surprisingly, the seed set in two bees was significantly lower than that of one bee in 'Rajah'. We suggest that honey bees prefer to visit already tripped florets or to visit fewer florets due to scent marks left by the previous honey bees. In open pollination, seed number per flower head in 'Amos' (on average 11) was half of 'Rajah' (on average 20). Seed set in 'Amos' was lower than 50% of 'Rajah' in honey bee (one bee treatment) and hand pollination (one and two pollen donors treatments). There were no differences in stigma receptivity whereas pollen viability in 'Amos' was lower than 'Rajah' after the peak pollen viability was reached (six days after the onset of flowering). We suggest that the fertility problems such as low pollen viability may be the reason for the low seed set in tetraploid red clover. This conclusion should be verified by investigating other fertility traits during the ovary, embryo and seed development with a broader range of diploid and tetraploid cultivars. [ABSTRACT FROM AUTHOR]

Climate change is likely to alter both flowering phenology and water availability for plants. Either of these changes alone can affect pollinator visitation and plant reproductive success. The relative impacts of phenology and water, and whether they interact in their impacts on plant reproductive success remain, however, largely unexplored. We manipulated flowering phenology and soil moisture in a factorial experiment with the subalpine perennial Mertensia ciliata (Boraginaceae). We examined responses of floral traits, floral abundance, pollinator visitation, and composition of visits by bumblebees vs. other pollinators. To determine the net effects on plant reproductive success, we also measured seed production and seed mass. Reduced water led to shorter, narrower flowers that produced less nectar. Late flowering plants produced fewer and shorter flowers. Both flowering phenology and water availability influenced pollination and reproductive success. Differences in flowering phenology had greater effects on pollinator visitation than did changes in water availability, but the reverse was true for seed production and mass, which were enhanced by greater water availability. The probability of receiving a flower visit declined over the season, coinciding with a decline in floral abundance in the arrays. Among plants receiving visits, both the visitation rate and percent of non-bumblebee visitors declined after the first week and remained low until the final week. We detected interactions of phenology and water on pollinator visitor composition, in which plants subject to drought were the only group to experience a late-season resurgence in visits by solitary bees and flies. Despite that interaction, net reproductive success measured as seed production responded additively to the two manipulations of water and phenology. Commonly observed declines in flower size and reward due to drought or shifts in phenology may not necessarily result in reduced plant reproductive success, which in M. ciliata responded more directly to water availability. The results highlight the need to go beyond studying single responses to climate changes, such as either phenology of a single species or how it experiences an abiotic factor, in order to understand how climate change may affect plant reproductive success.

The apparent climatic extremes affect the growth and developmental process of cool-season grain legumes, especially the high-temperature stress. The present study aimed to investigate the impacts of high-temperature stress on crop phenology, seed set, and seed quality parameters, which are still uncertain in tropical environments. Therefore, a panel of 150 field pea genotypes, grouped as early (n = 88) and late (n = 62) maturing, were exposed to high-temperature environments following staggered sowing [normal sowing time or non-heat stress environment (NHSE); moderately late sowing (15 days after normal sowing) or heat stress environment-I (HSE-I); and very-late sowing (30 days after normal sowing) or HSE-II]. The average maximum temperature during flowering was about 22.5 ± 0.17°C for NHSE and increased to 25.9 ± 0.11°C and 30.6 ± 0.19°C in HSE-I and HSE-II, respectively. The average maximum temperature during the reproductive period (RP) (flowering to maturity) was in the order HSE-II (33.3 ± 0.03°C) > HSE-I (30.5 ± 0.10°C) > NHSE (27.3 ± 0.10°C). The high-temperature stress reduced the seed yield (24–60%) and seed germination (4–8%) with a prominent effect on long-duration genotypes. The maximum reduction in seed germination (>15%) was observed in HSE-II for genotypes with >115 days maturity duration, which was primarily attributed to higher ambient maximum temperature during the RP. Under HSEs, the reduction in the RP in early- and late-maturing genotypes was 13–23 and 18–33%, suggesting forced maturity for long-duration genotypes under late-sown conditions. The cumulative growing degree days at different crop stages had significant associations (p < 0.001) with seed germination in both early- and late-maturing genotypes; and the results further demonstrate that an extended vegetative period could enhance the 100-seed weight and seed germination. Reduction in seed set (7–14%) and 100-seed weight (6–16%) was observed under HSEs, particularly in HSE-II. The positive associations of 100-seed weight were observed with seed germination and germination rate in the late-maturing genotypes, whereas in early-maturing genotypes, a negative association was observed for 100-seed weight and germination rate. The GGE biplot analysis identified IPFD 11-5, Pant P-72, P-1544-1, and HUDP 11 as superior genotypes, as they possess an ability to produce more viable seeds under heat stress conditions. Such genotypes will be useful in developing field pea varieties for quality seed production under the high-temperature environments.

The apparent climatic extremes affect the growth and developmental process of cool-season grain legumes, especially the high-temperature stress. The present study aimed to investigate the impacts of high-temperature stress on crop phenology, seed set, and seed quality parameters, which are still uncertain in tropical environments. Therefore, a panel of 150 field pea genotypes, grouped as early (n = 88) and late (n = 62) maturing, were exposed to high-temperature environments following staggered sowing [normal sowing time or non-heat stress environment (NHSE); moderately late sowing (15 days after normal sowing) or heat stress environment-I (HSE-I); and very-late sowing (30 days after normal sowing) or HSE-II]. The average maximum temperature during flowering was about 22.5 ± 0.17°C for NHSE and increased to 25.9 ± 0.11°C and 30.6 ± 0.19°C in HSE-I and HSE-II, respectively. The average maximum temperature during the reproductive period (RP) (flowering to maturity) was in the order HSE-II (33.3 ± 0.03°C) > HSE-I (30.5 ± 0.10°C) > NHSE (27.3 ± 0.10°C). The high-temperature stress reduced the seed yield (24–60%) and seed germination (4–8%) with a prominent effect on long-duration genotypes. The maximum reduction in seed germination (>15%) was observed in HSE-II for genotypes with >115 days maturity duration, which was primarily attributed to higher ambient maximum temperature during the RP. Under HSEs, the reduction in the RP in early- and late-maturing genotypes was 13–23 and 18–33%, suggesting forced maturity for long-duration genotypes under late-sown conditions. The cumulative growing degree days at different crop stages had significant associations (p < 0.001) with seed germination in both early- and late-maturing genotypes; and the results further demonstrate that an extended vegetative period could enhance the 100-seed weight and seed germination. Reduction in seed set (7–14%) and 100-seed weight (6–16%) was observed under HSEs, particularly in HSE-II. The positive associations of 100-seed weight were observed with seed germination and germination rate in the late-maturing genotypes, whereas in early-maturing genotypes, a negative association was observed for 100-seed weight and germination rate. The GGE biplot analysis identified IPFD 11-5, Pant P-72, P-1544-1, and HUDP 11 as superior genotypes, as they possess an ability to produce more viable seeds under heat stress conditions. Such genotypes will be useful in developing field pea varieties for quality seed production under the high-temperature environments. [ABSTRACT FROM AUTHOR]

Cryopreservation of pollen is a complementary conservation strategy and can be used for conserve the diversity in the genus Psidium. The present study aims to cryopreserve the pollen of Psidium species to overcome asynchronous flowering. The pollen of different Psidium species were germinated in vitro in an optimized medium of germination. In vitro / in vivo pollen viability assessment and SEM analysis were carried out to determine the changes after cryopreservation. The in vitro pollen viability was determined at monthly intervals starting from fresh pollen until six months of cryopreservation. The in vivo fertility tests were carried out by pollination using both fresh and cryopreserved pollen. The cryopreserved pollen showed in vitro germination ranging from 1.78% (in P. molle) to 81.67% (in "H 12–5") compared to fresh pollen (2.16% in P. molle to 86.08% in P. guineense). In vivo fertility was tested by controlled pollination using six-month-old cryopreserved pollen and it resulted in fruit setting ranged between 3.33% (P. cattleianum var. cattleianum) and 27.66% (P. chinensis) as compared to fresh pollen between 4.0% (P. cattleianum var. cattleianum) and 30.66% (P. chinensis). Seed set and germination was also recorded in all the crosses attempted using cryopreserved pollen. These in vitro and in vivo results indicated that cryopreservation is an effective technique for breeding and conserving the haploid gene pool in cryo genebank. Scanning Electron Microscopic studies of pollen revealed no significant variation in shape and size after cryopreservation when compared to fresh pollen. • Method of collection and optimum pollen germination media for different Psidium species were standardized. • Cryopreservation of pollen of wild Psidium species were carried to overcome asynchronous flowering and used for wide hybridization resulted in fruit and seed set. • Pollen morphology assessment of fresh and cryopreserved pollen in guava genotypes and wild Psidium species using SEM. • A pollen cryobank established for Psidium genotypes. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) is a self-pollinating crop whose hybrids offer the potential to provide a major boost in yield. Male sterility induced by the cytoplasm of Triticum timopheevii is a powerful method for hybrid seed production. Hybrids produced by this method are often partially sterile, and full fertility restoration is crucial for wheat production using hybrid cultivars. To identify the genetic loci controlling fertility restoration in wheat, we produced two cytoplasmic male-sterile (CMS) backcross (BC1) mapping populations. The restorer lines Gerek 79 and 71R1203 were used to pollinate the male-sterile winter wheat line CMS-Sperber. Seed set and numbers of sterile spikelets per spike were evaluated in 340 and 206 individuals of the populations derived from Gerek 79 and 71R1203, respectively. Genetic maps were constructed using 930 and 994 single nucleotide polymorphism (SNP) markers, spanning 2,160 and 2,328 cM over 21 linkage groups in the two populations, respectively. Twelve quantitative trait loci (QTL) controlled fertility restoration in both BC1 populations, including a novel restorer-of-fertility (Rf) locus flanked by the SNP markers IWB72413 and IWB1550 on chromosome 6AS. The locus was mapped as a qualitative trait in the BC1 Gerek 79 population and was designated Rf9. One hundred-nineteen putative candidate genes were predicted within the QTL region on chromosome 6AS. Among them were genes encoding mitochondrial transcription termination factor and pentatricopeptide repeat-containing proteins that are known to be associated with fertility restoration. This finding is a promising step to better understand the functions of genes for improving fertility restoration in hybrid wheat.

The seed setting, combining ability and heterobeltiosis analysis was carried out in gladiolus (Gladiolus grandiflorus L.) based on 5 × 5 full diallel mating for different traits utilizing five genotypes, viz. ACC-15, ACC-13, ACC-11, ACC-14 and ACC-04 for the experiment. Experimental results revealed that days required for maturity of capsules, harvest percentage of capsule, number of seeds per capsule, hundred seeds weight and seed germination percentage were varied significantly among the crosses. The maximum harvestable capsules was recorded in ACC-13 × ACC- 14 and its reciprocal cross while maximum number of seeds per capsule was found in the cross ACC-15 × ACC-13. The genotypes, viz. ACC-15, ACC-11 and ACC-14 were good general combiners for most characters for many traits. ACC-04 × ACC-14 had the highest SCA effects for diameter of cormel and can be used in both yield and quality improvement. Though, most of crosses showed a negative mid-parent and high-parent heterosis, hybrids expressing the highest MPH and HPH heterosis overall, were ACC-15 × ACC-13, ACC-14 × ACC-15 and ACC-04 × ACC-14.

Soybean production in southwestern Japan tends to be unstable owing to wet soils during the rainy season. Although late sowing after the rainy season can avoid excess water, information on its yield potential is limited. The objective of this study was to reveal the effect of late sowing on yields and yield components of new soybean cultivars developed for warm regions. The experiment was conducted in 2016 and 2017 in Fukuyama, Hiroshima, Japan. Upland fields converted from paddy fields with a subirrigation system were planted in June (normal) or July (late sparse or late dense). Lodging was prevented with a net. The effects of late sowing and dense treatment were analyzed in relation to solar radiation use. In 2016, differences in yield among cultivars and among environments were not significant. In 2017, yield was significantly reduced following late sparse sowing. The total aboveground dry matter at maturity was correlated with total solar radiation intercepted (r = 0.76) but not with radiation use efficiency (r = 0.47). Late sowing increased harvest index (HI) significantly from 0.464 to 0.571 in 2016 and from 0.524 to 0.585 in 2017, but density had no significant effect. The changes in HI were correlated with stem dry weight (r = −0.80 in 2016 and r = −0.79 in 2017) rather than seed yield (r = 0.08, n.s. in 2016 and r = 0.19, n.s. in 2017). Thus, under irrigation, late dense sowing might stabilize yield in southwestern Japan because of higher HI. Abbreviations: DM: dry matter; FOEAS: farm-oriented enhancing aquatic system; HI: harvest index; RUE: radiation use efficiency

Abstract Background A large proportion of the flowers and ovules of plants do not develop into fruits and seeds. Plant reproduction may be limited because of pollen limitation and resource limitation. Medicago sativa L. is an ecologically important species in northwest China. We conducted a pollen supplementation experiment to determine the degree of pollen limitation in this species and detect the possible effects of resource allocation on pollen supplementation. We crossed two factors, pollen level (natural condition and hand pollinated) and resource level (control, water added, and fertilizer added), to estimate the effects of pollen addition and resource limitation on the opening of flowers and seed set. We also analyzed the floral characters, visitation frequency of pollinators and pollinator activity to estimate the effect of pollinators on the reproduction of M. sativa. Results Our results indicated that addition of pollen to some flowers did not divert resources from other flowers and that the addition of pollen boosted the seed set per flower, with no effect on flower number. The primary effect of resource limitation was on the number of flowers produced; however, there was no significant effect on seed set per flower. These findings showed that pollen limitation was an important limiting factor for seed set. In addition, Andrena lebedevi Popov was identified as the most effective pollinator, and pollinator visiting and activity affected reproduction success in M. sativa. Conclusions We found outcrossing was dominant in the breeding system and insect pollination played an important role in outcrossing. These findings have identified the dominant factor influencing seed set of M. sativa. This study aspires to contribute to a better understanding of pollen limitation, resource limitation and reproductive success.

Maximizing seed yield is the ultimate breeding goal in important cereal crop species. Seed set is a key developmental stage in the process of seed formation, which determines grain number, seed mass, and realized yield potential, and can be severely affected by abiotic and biotic stresses. However, seed set can also be substantially reduced by genetic factors even under optimal fertilization conditions. The underlying molecular genetic mechanisms are still obscure. In this review, we elucidate the process of seed set of cereal crop species in detail, including development of floral structures, formation of viable gametes, double fertilization, seed development, and abortion. We discuss how genetic and non-genetic factors affect seed set in different development stages. Finally, we will propose novel strategies to study genetic mechanisms controlling seed set and exploit genetic resources to improve seed set in cereal crop species.

Wheat (Triticum aestivum L.) is a self-pollinating crop whose hybrids offer the potential to provide a major boost in yield. Male sterility induced by the cytoplasm of Triticum timopheevii is a powerful method for hybrid seed production. Hybrids produced by this method are often partially sterile, and full fertility restoration is crucial for wheat production using hybrid cultivars. To identify the genetic loci controlling fertility restoration in wheat, we produced two cytoplasmic male-sterile (CMS) backcross (BC1) mapping populations. The restorer lines Gerek 79 and 71R1203 were used to pollinate the male-sterile winter wheat line CMS-Sperber. Seed set and numbers of sterile spikelets per spike were evaluated in 340 and 206 individuals of the populations derived from Gerek 79 and 71R1203, respectively. Genetic maps were constructed using 930 and 994 single nucleotide polymorphism (SNP) markers, spanning 2,160 and 2,328 cM over 21 linkage groups in the two populations, respectively. Twelve quantitative trait loci (QTL) controlled fertility restoration in both BC1 populations, including a novel restorer-of-fertility (Rf) locus flanked by the SNP markers IWB72413 and IWB1550 on chromosome 6AS. The locus was mapped as a qualitative trait in the BC1 Gerek 79 population and was designated Rf9. One hundred-nineteen putative candidate genes were predicted within the QTL region on chromosome 6AS. Among them were genes encoding mitochondrial transcription termination factor and pentatricopeptide repeat-containing proteins that are known to be associated with fertility restoration. This finding is a promising step to better understand the functions of genes for improving fertility restoration in hybrid wheat. [ABSTRACT FROM AUTHOR]

Herbivores decrease plant fitness by consuming reproductive tissues, limiting resources, and/or affecting mutualisms. Although these mechanisms were extensively tested in chewing herbivores, the impact of other functional groups (e.g., sap-feeders) remains poorly understood. We investigated whether aphids affect plant reproduction via direct resource limitation on seed production and/or pollination interference. We compared plant traits and the seed set of naturally aphid-free vs. aphid-infested plants and then manipulated aphid presence and pollen receipt. We used path models to examine the links between variables. Nectar volume and seed set of aphid-infested plants was 54% and 42% lower than that of aphid-free plants. 72 h after removing aphids, nectar volume was restored to the level of aphid-free plants. When pollinators were excluded, the seed set of aphid-infested and aphid-free plants did not differ, suggesting that direct resource limitation on seed production was not the cause of reduced plant fitness. Manual addition of pollen restored the seed set of aphid-infested plants to the level of aphid-free plants, evidencing that plants were pollen limited. The path analysis showed a negative link between aphids and the seed set via nectar volume, supporting that nectar shortage caused by aphids may interfere with pollination and reduce plant fitness. Since aphids are crop pests and feed on a large number of animal-pollinated plants, the potential of these insects to influence pollination and plant fitness is high. This study emphasizes the ecological importance of aphids and the need to better understand the links between sap-feeding herbivory, pollination, and plant fitness. [ABSTRACT FROM AUTHOR]

Habitat remnants act as a source of pollinators potentially relevant for crop pollination and yield. This work analyzes how habitat loss influences pollinators, effective pollination and yield of soybean crops. The study area comprises ten sites adjacent to forest patches surrounded by a soybean matrix in central Argentina (eight sites in the season 2014–2015 and two sites in the season 2015–2016). Pollination was estimated by pollen deposition and frequency of flower visitors. Pollen deposition on stigmas and seed set were measured comparing open plants and plants with pollinator exclusion. These response variables were compared considering increasing distance to the forest edge and an increasing gradient of forest patch size. Bees were the most frequent visitors of soybean flowers, especially honeybees, but also at least three native bee species were recorded. Open plants showed higher rates of stigmatic pollen deposition than plants with pollinator exclusion, but seed set was similar. Total insect visitation rates, especially of native insects, decreased with distance to the forest edge and so did pollen deposition. Pollen deposition and seed set increased with increasing forest patch size for plants located near and far from the forest edge, respectively. Overall, our results suggest that the contribution of native pollinators from local forest patches is important for effective pollination across the landscape. Small patches of forest (approximately 1 ha.) guarantee pollinators to ensure plant yields similar to the yields of plants growing close to large patches, but only at short distances; while larger forest patches provide better pollination services for the crop at larger distances from the forest edge. However, we encourage further studies because results suggest that other factors may also influence soybean pollination and production. [ABSTRACT FROM AUTHOR]

Phacelia tanacetifolia is a widely used food plant in the beekeeping and conservation of pollinators. The present work is the first report for its value as bees and insectary plants in Saudi Arabia. Insect species visiting on flowers of P. tanacetifolia were identified and clustered as pollinators, pests and natural enemies. Out of 54 recorded insect species, 26 species were from Hymenoptera followed by Diptera (eight species), Lepidoptera (eight species), Coleoptera (six species), Hemiptera (five species) and Neuroptera (one species). Hymenopterous insect (bees, wasps, and ants) were the abundant flower visitors and out of them, bees were at the top with the highest recorded species (18). Apis mellifera and Apis florea were the most common honey bee species visiting on P. tanacetifolia, and exhibited daytimes and flowering season-dependent foraging activity (visits/m2). Apis species showed preferential high foraging visits for nectar than pollen collection. The major flower visitor was A. florea and the time spent by A. florea in the flower was significantly higher than A. mellifera. Insect-pollinated flowers of P. tanacetifolia presented significantly high-seed set percentage (62%) than non-insect-pollinated flowers (14%). Nectar secretion of P. tanacetifolia fluctuated significantly during daytimes and months with the highest amount during noon-afternoon and March. Blooming period (six weeks: fore-March to mid-April), seed harvesting (late-April), flower density (9069 flowers/m2/day), nectar productivity (4 g/m2/day) and honey potentiality (1791 kg/ha/season) of P. tanacetifolia was also monitored. P. tanacetifolia can be an ideal potential plant to support honey bees and other insect pollinators in the hot-dry ecosystem of central Saudi Arabia. [ABSTRACT FROM AUTHOR]

Researchers have long assumed that plant spatial location influences plant reproductive success and pollinator foraging behaviour. For example, many flowering plant populations have small, linear or irregular shapes that increase the proportion of plants on the edge, which may reduce mating opportunities through both male and female function. Additionally, plants that rely on pollinators may be particularly vulnerable to edge effects if those pollinators exhibit restricted foraging and pollen carryover is limited. To explore the effects of spatial location (edge vs. interior) on siring success, seed production, pollinator foraging patterns and pollen-mediated gene dispersal, we established a square experimental array of 49 Mimulus ringens (monkeyflower) plants. We observed foraging patterns of pollinating bumblebees and used paternity analysis to quantify male and female reproductive success and mate diversity for plants on the edge versus interior. We found no significant differences between edge and interior plants in the number of seeds sired, mothered or the number of sires per fruit. However, we found strong differences in pollinator behaviour based on plant location, including 15 % lower per flower visitation rates and substantially longer interplant moves for edge plants. This translated into 40 % greater pollen-mediated gene dispersal for edge than for interior plants. Overall, our results suggest that edge effects are not as strong as is commonly assumed, and that different plant reproduction parameters respond to spatial location independently. [ABSTRACT FROM AUTHOR]

Summary: Heat stress during flowering has differential impact on male and female reproductive organ viability leading to yield losses in field crops. Unlike flooded rice, dryland cereals such as sorghum, pearl millet and wheat have optimised their flower opening during cooler early morning or late evening hours to lower heat stress damage during flowering. Although previous studies have concluded that pollen viability determines seed set under heat stress, recent findings have revealed pearl millet and sorghum pistils to be equally sensitive to heat stress. Integrating flower opening time during cooler hours with increased pollen and pistil viability will overcome heat stress‐induced damage during flowering under current and future hotter climatic conditions. [ABSTRACT FROM AUTHOR]

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Lantana camara is an important plant for the environmental horticultural industry, yet it can be invasive, cross-pollinating with native lantana and dispersing fruit (and seeds) to natural and agricultural lands. Identification and development of sterile cultivars is much needed to meet industry and consumer needs for noninvasive plant materials. Previously we evaluated the male fertility of 32 L. camara cultivars/breeding lines at five ploidy levels. This study was to assess their female fertility and understand the relationship between female fertility and ploidy level and the production of unreduced female gametes (UFGs) in L. camara. These cultivars/breeding lines significantly varied in percent fruiting plants (6.3% to 100.0%), percent fruiting peduncles (0.3% to 98.8%), fruit per peduncle (0.003 to 7.173), seed germination (0% to 57.1%), and female fertility index (0.003 to 2.998). Certain diploids (e.g., 'Denholm White') were highly female- sterile. Eleven of the 13 triploids evaluated were UFG-producing and rather fertile. The two non-UFG-producing triploids had the female fertility index of 0.005, thus most sterile. Tetraploids, especially those producing UFGs, were prolific fruit producers. These results show that ploidy level and UFG production play a significant role in determining fruit (seed) production capacity and female fertility of L. camara. None of the commercial triploid cultivars evaluated reached desirable levels of male and female sterility, indicating a strong need to develop new lantana cultivars that are male- and female-sterile. Our results suggest that production and selection of triploids can be effective to sterilize L. camara, but it is imperative to select diploids and tetraploids that do not produce UFGs as the breeding parents. [ABSTRACT FROM AUTHOR]

In the intense solar radiation of an alpine climate, small black bees often experience extremely high thoracic temperatures when they are foraging on flowers, but flies forage at lower temperatures. To explore the hypothesis that seed set could be depressed by transient dehydration of pollen at the high temperatures reached by hot bees foraging in sunshine, we compared the effectiveness of single visits by different pollinators to a bowl-shaped flower Potentilla lancinata in alpine meadows, SW China. The ratio of seed set to pollen transferred in individual flowers was monitored over 2 years, indicating that pollen deposited on stigmas by halictid bees produced lower seed set than pollen carried by flies. Scopal pollen applied to stigmas by hand gave good seed set, but in germination tests it burst more frequently than pollen from anthers, implying dehydration. Pollen grains freshly taken from the scopae of solitary bees foraging in sunshine were smaller than those taken from anthers or foraging bees in early-morning overcast conditions, implying dehydration. The effect was reversible: hand pollination showed that scopal pollen was no less effective than fly pollen after removal from the bee. Pollen carried by such bees foraging in intense sunlight in flowers became dehydrated, causing an osmotic mismatch between the pollen and the stigmas. Transient heat-induced dehydration of pollen represents a novel pathway by which climate warming may disrupt plant reproduction, and helps us understand why flies could be more effective pollinators than bees in cool, high-radiation arctic or high-altitude sites. [ABSTRACT FROM AUTHOR]

Due to ongoing human impacts, plant species increasingly occur in landscapes that are highly fragmented, with remaining natural habitats occupying small areas, resulting in populations that are smaller and more isolated than in previous time periods. This changed metapopulation structure is expected to have negative impacts on seed production. For example, the proportion of female plants within gynodioecious populations may be more volatile due to genetic drift in small populations associated with small habitat fragments, with concomitant impacts on seed production. My aims were to determine: (i) if variation in proportion of females is larger in smaller fragments; and (ii) if such changes in female frequency in small fragments result in reduced seed production.Thirty‐two populations of Lobelia spicata Lam., a gynodioecious species, were surveyed in 2000, 2001 and 2009 in the tallgrass prairie region of Midwestern North America (Illinois and Indiana, USA). Data were collected for: proportion of female plants, total number of flowering plants (measure of population size), seed set per plant and prairie fragment size (another measure of population size).The proportion of females is more variable in smaller prairie fragments. Seed number per fruit decreases as the proportion of females increases in a population, but only significantly for female plants. The number of flowering plants is positively associated with fruit production for both genders. Populations within larger prairie fragments have higher seed production.The reproductive consequences of habitat fragmentation depend on the plant breeding system. While both sexes were negatively impacted, females were more adversely affected. [ABSTRACT FROM AUTHOR]

The fig (Moraceae) and pollinating fig wasp (Agaonidae) mutualism is best known as a model system for the study of coevolution in plant–pollinator interactions and its central role in shaping vertebrate communities in tropical forests. Figs also host myriad antagonistic parasitic fig wasps which impose costs on both partners threatening mutualism stability. Spatiotemporal variation in parasitic wasp abundance is a key factor in mitigating these effects. Because fig wasps are temperature sensitive and likely vary in their ability to traverse environmental gradients, we expect community assemblages and abundance of both pollinating and non‐pollinating fig wasps to respond to changes along an elevational gradient. In the present study, we compare the fig wasp communities and abundance of three fig species growing along the slopes of the Mount Wilhelm altitudinal gradient in Papua New Guinea. We quantified wasps from over 100 male fig trees and calculated seed set for 55 female trees along each of the species' distribution on the transect. Our results show that the abundance of both pollinating and non‐pollinating fig wasps follow a mid‐elevation peak, consistent with fig species richness found in the same transect. The patterns, however, are different according to the host's species distribution. Seed set remained relatively constant along the gradient for all species with some decrease along higher elevations, potentially affecting connectivity along the gradient. As suggested for insects in general, temperature and habitat diversity appear to play a fundamental role in the species richness and abundance of fig wasps. [ABSTRACT FROM AUTHOR]

Climate change-induced increases in the frequency of extreme weather events, particularly heatwaves, are a serious threat to crop productivity. The productivity of grain crops is dependent on the success of sexual reproduction, which is very sensitive to heat stress. Male gametophyte development has been identified as the most heat-vulnerable stage. This review outlines the susceptibility of the various stages of sexual reproduction in flowering plants from the time of floral transition to double fertilization. We summarize current knowledge concerning the molecular mechanisms underpinning the heat stress-induced aberrations and abnormalities at flowering, male reproductive development, female reproductive development, and fertilization. We highlight the stage-specific bottlenecks in sexual reproduction, which regulate seed set and final yields under high-temperature conditions, together with the outstanding research questions concerning genotypic and species-specific differences in thermotolerance observed in crops. This knowledge is essential for trait selection and genetic modification strategies for the development of heat-tolerant genotypes and high-temperature-resilient crops. [ABSTRACT FROM AUTHOR]

Abstract Background We studied the life history of Gagea graeca (L.) A. Terracc. (sect. Anthericoides) by field surveys on the Greek island of Crete, including quantitative analyses of 405 individuals, estimation of resource allocation by measuring the nitrogen content of different plant organs, assessing seed set and recording genetic diversity via amplified fragment length polymorphism (AFLP) analyses. In contrast to most species of the genus G. graeca seems to be a short-lived perennial, developing several characters that are rather typical for annual plants. Results Although seed set varies largely, flowering plants produce many (68 ± 79) small, flattened seeds (mean weight 73 ± 22 µg) in comparison to a single bulbil. If measured as nitrogen content of the respective plant parts, investment in seeds (25%) is much higher than that in bulbils (4%). In addition, the threshold for flower formation (expressed as bulb size where 50% of the plants form the respective structure) is with 2.17 ± 0.05 mm lower than that for bulbils with 2.80 ± 0.16 mm. This is in accordance with AFLP analyses revealing predominantly sexual reproduction (only 9.1% of 110 investigated plants belonged to clones). Conclusion In the genus Gagea early, predominantly sexual reproduction seems to be characteristic for species from arid habitats, coupled with a low proportion of clonal plants.

Polyamines (PAs) constituting putrescine (Put), spermidine (Spd), and spermine (Spm) are ubiquitous in all organisms and play essential roles in the growth and developmental processes in living organisms, including plants. Evidences obtained through genetic, biochemical, and transgenic approaches suggest a tight homeostasis for cellular PA levels. Altered cellular PA homeostasis is associated with abnormal phenotypes. However, the mechanisms involved for these abnormalities are not yet fully understood, nor is it known whether cellular ratios of different polyamines play any role(s) in specific plant processes. We expressed a yeast spermidine synthase gene (ySpdSyn) under a constitutive promoter CaMV35S in tomato and studied the different phenotypes that developed. The constitutive expression of ySpdSyn resulted in variable flower phenotypes in independent transgenic lines, some of which lacked fruit and seed set. Quantification of PA levels in the developing flowers showed that the transgenic plants without fruit and seed set had significantly reduced Spd levels as well as low Spd/Put ratio compared to the transgenic lines with normal fruit and seed set. Transcript levels of SlDELLA, GA-20oxidase-1, and GA-3oxidase-2, which impact gibberellin (GA) metabolism and signaling, were significantly reduced in bud tissue of transgenic lines that lacked fruit and seed set. These findings indicate that PAs, particularly Spd, impact floral organ identity and fruit set in tomato involving GA metabolism and signaling. Furthermore, we suggest that a nexus exists between PA ratios and developmental programs in plants.

Grain legumes provide a rich resource of plant nutrition to human diets and are vital for food security and sustainable cropping. Heat stress during flowering has a detrimental effect on legume seed yield, mainly due to irreversible loss of seed number. To start with, we provide an overview of the developmental and physiological basis of controlling seed setting in response to heat stress. It is shown that every single process of seed setting including male and female gametophyte development, fertilization, and early seed/fruit development is sensitive to heat stress, in particular male reproductive development in legume crops is especially susceptible. A series of physiochemical processes including heat shock proteins, antioxidants, metabolites, and hormones centered with sugar starvation are proposed to play a key role in regulating legume seed setting in response to heat stress. The exploration of the molecular mechanisms underlying reproductive heat tolerance is in its infancy. Medicago truncatula, with a small diploid genome, and well-established transformation system and molecular platforms, has become a valuable model for testing gene function that can be applied to advance the physiological and molecular understanding of legume reproductive heat tolerance.

Haloxylon ammodendron (C. A. Mey.) Bunge is an ecologically important species in arid regions. Pollen limitation may decrease plant reproduction due to low levels of pollen transfer and inadequate pollen receipt. In arid regions, pollen limitations of many plant species may be influenced by habitat fragmentation. However, whether pollen limitation and pollinator visitation affect the pollination success of H. ammodendron (Amaranthaceae) in fragmented habitats still needs further study. In this study, we calculated the pollen limitation in natural and fragmented habitats to estimate the effect of habitat fragmentation on pollen limitation. In different habitats, we investigated the relationship between the number of open flowers and pollinator visiting frequency. In addition, we examined how habitat fragmentation affects pollination success through the influence of pollinator visitation rate on seed set. Our results indicated that pollen limitation was the important limiting factor for seed set in fragmented and natural habitats. The results showed higher pollinator visitation rates resulted in a higher percentage of seeds in both habitats. In H. ammodendron, Apis mellifera was found to be the dominant pollinator. These results may support the assertion that plants evolve traits to attract pollinators and pollinators increase their visiting frequency to better exploit the floral resources. We also determined that outcrossing was dominant in the breeding system and that wind pollination played an important role in pollination success. This study aims to contribute to a better understanding of how environmental heterogeneity affects pollen limitation, pollinator visitation, and pollination success in arid regions.

Sucrose non-fermenting-1-related protein kinase-1 (SnRK1) is a highly conserved serine-threonine kinase complex regulating plants' energy metabolisms and resistance to various types of stresses. However, the downstream genes regulated by SnRK1 in these plant physiological processes still need to be explored. In this study, we found that the knockout of OsSnRK1a resulted in no obvious defects in rice growth but notably decreased the seed setting rate. The ossnrk1a mutants were more sensitive to blast fungus ( Magnaporthe oryzae ) infection and showed compromised immune responses. Transcriptome analyses revealed that SnRK1a was an important intermediate in the energy metabolism and response to biotic stress. Further investigation confirmed that the transcription levels of OsNADH-GOGAT2 , which positively controls rice yield, and the defense-related gene pathogenesis-related protein 1b ( OsPR1b ) were remarkably decreased in the ossnrk1a mutant. Moreover, we found that OsSnRK1a directly interacted with the regulatory subunits OsSnRK1β1 and OsSnRK1β3, which responded specifically to blast fungus infection and starvation stresses, respectively. Taken together, our findings provide an insight into the mechanism of OsSnRK1a, which forms a complex with specific β subunits, contributing to rice seed set and resistance by regulating the transcription of related genes.

Seed set in East African Highland Cooking bananas (EAHBs) is extremely low and therefore hampers breeding. Pollen–pistil interaction is a key contributing factor. We assessed the effect of pollen germination media (PGM) on seed set in EAHBs. Five EAHB cultivars were pollinated with pollen from the wild banana ‘Calcutta 4’. Glucose-based PGM sprayed on freshly emerged stigmas significantly increased seed set per 100 fruits per bunch. Increases were 73.5% in ‘Enzirabahima’, 39.9% in ‘Mshale’, and 302.4% in ‘Nshonowa’. However, PGM did not increase seed set in the female sterile ‘Mlelembo’ and ‘Nakitembe’. As larger bunches were more fertile, good field management practices are also recommended to get more seed to improve breeding efficiency.

Greater pollination intensity can enhance maternal plant fitness by increasing seed set and seed quality as a result of more intense pollen competition or enhanced genetic sampling. We tested experimentally these effects by varying the pollen load from a single pollen donor on stigmas of female flowers of Dalechampia scandens (Euphorbiaceae) and measuring the effects on seed number and seed mass. Seed set increased rapidly with pollen number at low to moderate pollen loads, and a maximum set of three seeds occurred with a mean pollen load of 19 pollen grains. We did not detect a trade‐off between the number of seeds and seed mass within a fruit. Seed mass increased with increasing pollen load, supporting the hypothesis of enhanced seed quality via increased pollen‐competition intensity or genetic sampling. These results suggest that maternal fitness increases with larger pollen loads, even when the fertilization success is already high. Our results further highlight the importance of high rates of pollen arrival onto stigmas, as mediated by reliable pollinators. Comparing the pollen‐to‐seed response curve obtained in this experiment with those observed in natural populations suggests that pollen limitation may be more severe in natural populations than predicted from greenhouse studies. These results also indicate that declines in pollinator abundance may decrease plant fitness through lowered seed quality before an effect on seed set is detected. [ABSTRACT FROM AUTHOR]

A field experiment was conducted at the experimental fields in the College of Agricultural Engineering Sciences, University of Baghdad, Iraq from beginning of April 2017 to the end of August 2018. The main objective was to find out the effect of potassium (K) concentration (0, 1, 2 and 3 g.L-1) and three stages of foliar application (vegetative growth, beginning of flowers buds emergence and 25% flowering) on seed yield and its components of alfalfa local cultivar. Layout of the experiment was R.C.B.D. arranged in split-plot, with three replications. Foliar application stages were used as main-plots, while potassium concentrations were used as sub-plot. Results showed that spraying of K at conc. 3 g L-1 resulted in a significant increment in the number of stems m-2, number of racemes stem-1, number of florets raceme-1, number of pods raceme-1, number of seeds pod-1 and seed yield. While % of florets abortion was not significantly influenced by K concentration. Highest 1000 seed weight was obtained when no K added (control treatment). Highest seed yield (439.1 kg ha-1) was obtained when K sprayed at conc. 3 gL-1. Plants sprayed at vegetative growth produces highest number of florets raceme-1, number of pods raceme-1, number of seeds pod-1 and seed yield (412.5 Kg ha-1). There were no significant effect of spraying stages on number of stems m-2, % of florets abortion and number of seeds pod-1. There were a significant interaction between. K conc. and spraying stages. The higher seed yield (537.0 kg ha-1) was obtained when alfalfa plants were sprayed with K at the conc. 3g L-1 in vegetative growth. [ABSTRACT FROM AUTHOR]

In wheat, water deficit during meiosis of pollen mother cells greatly reduces seed set and grain number. A promising option to avoid grain losses and maintain wheat productivity under water stress is to exploit conservative water-use strategies during reproduction. In this work, two cultivars known to be adapted to different environments were studied. Water stress, with or without a polymer spray known to reduce stomatal conductance, was applied to both cultivars just prior to meiosis. Two experiments were carried out in a phenotyping platform to (1) assess and validate daily non-destructive estimation of projected leaf area and to (2) evaluate different water-use (WU) strategies across the meiotic period and their effect on physiology and yield components. Gladius displays an elevated breakpoint (BP) in the regression of WU against fraction of transpirable soil water (FTSW) for both daily and night-time WU suggesting higher conservative whole-plant response when compared to Paragon. At the same time, Gladius maintained flag leaf gas-exchange with a significant reduction at ~ 0.2 FTSW only, suggesting an uncoupled mechanism of WU reduction that optimized the water resource available for flag leaf gas-exchange maintenance. Under progressive soil drying, seed set and grain number of tillers stressed at GS41 were significantly reduced in Paragon (p < 0.05) thus leading to lower grain yield and grain number at plant level than Gladius. Polymer-induced reduction of transpiration is potentially useful when applied to the non-conservative stressed Paragon, maintaining higher FTSW, water-use efficiency and RWC during the progressive soil drying treatment. This led to better seed set (p < 0.05) and grain number maintenance (p < 0.05) than in the stressed Paragon control. We conclude that the different conservative traits detected in this work, protect grain development around meiosis and therefore maintain grain number under water-limiting conditions. Additionally, non-conservative genotypes (often with a greater expected yield potential) can be protected at key stages by reducing their water use with a polymer spray. Thus, future efforts can integrate both crop breeding and management strategies to achieve drought-resilience during the early reproductive phase in wheat and potentially other cereals. [ABSTRACT FROM AUTHOR]

Autotetraploid rice is a new germplasm resource obtained by doubling chromosomes through colchicine treatment. There have been many studies on the reproductive characteristics of autotetraploid rice, but little is known about global DNA variations and reasons for low embryo sac fertility in autotetraploid rice. Therefore, an autotetraploid rice line (T446) was used for resequencing and embryo sac fertility was observed. Whole-genome resequencing data revealed 87,229 SNPs and 11,022 InDels in the genome of T446 versus E246 (diploid rice), which had an average of 23.37 SNPs and 2.95 InDels per 100 kb. A total of 17,375 and 17,171 structural variations and 131 and 128 copy number variations were identified in the autotetraploid and its diploid counterpart, respectively. We detected 140 large-effects SNPs and InDel variants that might be related to the embryo sac fertility of autotetraploid rice, including 10 genes that may be closely associated with the development of the embryo sac. Of these, Os02g0292600 and Os06g0565200 were specifically expressed in the ovary. Mature embryo sac fertility was observed through whole-mount eosin B-staining confocal laser scanning microscopy. Many abnormalities were found in the embryo sac of T446, including embryo sac degeneration, embryo sac without female germ unit, abnormal polar nuclei, and poly-eggs, which, in turn, resulted in low seed set. However, whole-genome polymorphisms and genetic differences were high and exhibited broad prospects for genetic improvement. Genetic mutations in genes associated with embryo sac fertility in polyploid rice require further studies. [ABSTRACT FROM AUTHOR]

Fragmentation of natural vegetation is currently one of the largest threats to plant populations and their interactions with pollinators. Plant reproductive susceptibility to habitat fragmentation has been investigated in many species; however, the response of wild mass‐flowering species is poorly known, with research limited to mainly boreal plant species.Here, we studied twelve remnant populations of the threatened mass‐flowering shrub Conospermum undulatum in the southwest Australian biodiversity hotspot, each presenting different population size, level of isolation, and floral display. We assessed the impact of fragmentation on (a) fruit and seed production; and (b) seed germination. To gain a deeper understanding of factors influencing the reproductive success of C. undulatum, we performed pollinator exclusion and self‐pollination treatments to experimentally assess the mating system of this threatened shrub.We found C. undulatum to be strictly self‐incompatible and totally reliant on pollinators visiting with an outcrossed pollen load to complete the reproductive cycle. Further, we found that fruit production dropped from 35% to <20% as a result of decreasing floral display. A reduction in population size from 880 to 5 plants and from ~700 to 0.21 in the floral display index led to a decrease in seed output, while a similar reduction in seed output, from 6% to 3%, was observed as a result of increasing isolation index from −21.41 to −0.04. Overall, seed germination was positively related to population size, and a negative relationship was found between germination and isolation.Synthesis and applications. Our results demonstrate the important relationship between pollinators and floral morphology in plants of southwest Australia that have coevolved with native pollinators and developed characteristic flower morphologies over long time frames. Indeed, due to its characteristic pollination mechanism, the self‐incompatible C. undulatum can only rely on specialized native pollinators for pollen flow and cannot rely on its mass‐flowering trait to attract generalist pollinators from coflowering species; neither can it compensate for the lack of visitors by promoting geitonogamy. Consequently, fragmentation has a significant effect on the reproductive output of C. undulatum, and size, isolation, and floral display of populations are important factors to be considered when planning conservation actions for the species. [ABSTRACT FROM AUTHOR]

The relationship between individual berry weight and viable seed number of small- (<15 mm), medium- (15-19 mm), and large-diameter (>19 mm) berries was studied over 2 years in nine cultivars (Aurora, Bluecrop, Bluegold, Draper, Duke, Liberty, Legacy, Ozarkblue, and Reka) through their harvest seasons. Plants were grown with two different preplant amendment-mulch treatments, but this treatment had no effect on the variables measured, so data were pooled. The highest average seeds/berry was in 'Bluecrop' (55.5) and 'Duke' (50.0) and the lowest in 'Bluegold' (17.1), 'Aurora' (22.5), and 'Liberty' (23.5). Average berry weight over the fruiting season ranged from 1.79 and 1.80 g for 'Liberty' and 'Reka', respectively, to 2.30 and 2.44 g in 'Ozarkblue' and 'Draper', respectively. The average number of seeds/berry was higher in 2010 than in 2009 for all cultivars, ranging from 14% higher in 'Reka' to 96% higher in 'Liberty'. The flowering period was earlier in 2010 than in 2009, but bloom was concentrated in 2009 (28 days) compared with 2010 (45 days), likely affecting pollinator success. In general, seeds/berry and berry weight declined through the harvest season. Some cultivars had a considerable difference in the number of seeds in large-sized than in small-sized berries (e.g., 89%, 107%, 108%, and 147% more seeds in 'Aurora', 'Reka', 'Bluegold', and 'Liberty', respectively), whereas others had relatively little difference (14% and 36% in 'Draper' and 'Bluecrop', respectively). There was a linear relationship between berry weight and viable seeds/berry. Cultivars did not differ in the berry weight per seed (slope of the line) between the 2 years, except for 'Draper' (only significant in 2009), 'Legacy', and 'Reka'. 'Bluegold' had the greatest berry weight per seed and 'Reka' the lowest. The weakest relationship between berry weight and seed number was in 'Draper'. Cultivars that produced parthenocarpic fruit of marketable size were 'Aurora', 'Bluegold', and 'Liberty'. 'Duke', 'Legacy', 'Reka', and 'Ozarkblue' produced commercially acceptable fruit (0.75-1.0 g) with fewer than 7 seeds/berry. By contrast, some cultivars required a relatively large number of seeds to produce a berry including 'Bluecrop' (28-40 seeds), 'Draper' (15-23 seeds), and 'Legacy' in 2010 (20 seeds). The number of seeds per berry accounted for as much as 87% of the variability in berry weight indicating the importance of good pollination and seed set for berry weight and yield in these cultivars. [ABSTRACT FROM AUTHOR]

Fragmentation of plant communities is generally considered to be detrimental to the survival of the constituent species, especially those that are rare. We investigated the effects of fragmentation on reproductive biology in nine populations of the rare taxon Banksia nivea subsp. uliginosa , differing in size and habitat context. Small mammals were the main pollinator, with lower contributions from honeybees and birds (honeyeaters). There was no significant relationship between population size, fruit set and seed germinability. Fruit set was marginally highest (25.5 ± 3.4) in medium size populations and was variable over years. Lower fruit set (1.0 ± 0.6) in the smallest population may be due to inbreeding depression or lack of pollinators in a degraded habitat, but low fruit set was also observed in the largest population despite high levels of gene flow, possibly due to low pollinator visitation rate in a low-density population. Seeds from all populations had high germination success (>93.4%). Predation occurred in up to 56% of fruit and increased with increasing population size, but was not significantly different between populations of different size. Our study provided evidence that the reproductive output in species in a naturally fragmented landscape system may be resilient to reduced population size and other influences of anthropogenic fragmentation. [ABSTRACT FROM AUTHOR]

Premise: Sexual dimorphism in flowering phenology traits may have evolved under sexual selection and vector‐mediated selection. The conspicuous sexual dimorphism and sex‐specific selection pressures in flowering phenology traits have been investigated mainly in entomophilous dioecious plants, whereas little is known about this in anemophilous plants. Methods: We examined sexual dimorphism in flowering onset, flowering peak, flowering duration, maximum proportion of open flowers per inflorescence branch, maximum proportion of newly opening flowers on a given date per branch, and longevity of individual flowers in natural Rumex acetosa populations. Correlations between flowering phenology traits and the degree of flowering overlap with the opposite sex were examined. We also tested whether the overlap of female flowering with male flowering enhanced seed set in female plants. Results: Little sexual dimorphism was observed in flowering onset, peak, duration, and maximum proportion of newly opening flowers. Females had greater floral longevity and greater maximum proportion of open flowers than males. Flowering overlap with the opposite sex significantly increased with the maximum proportion of newly opening flowers and decreased with temporal deviation in the flowering peak in both sexes. Females with greater flowering overlap with males set more seeds in two of the three study populations. Conclusions: In wind‐pollinated R. acetosa, little sexual dimorphism in phenological traits may have evolved to achieve synchronous flowering with the opposite sex. Our results suggest that, in angiosperms, not only common selection but also anemophily‐specific selection may shape little sexual dimorphism in R. acetosa, unlike in entomophilous plants. [ABSTRACT FROM AUTHOR]