Plant Breeding Systems Research Articles

The influence of environmental factors on breeding system allocation at large spatial scales.

Plant breeding systems can vary widely among populations, yet few studies have investigated abiotic factors contributing to variation across a broad geographic range. Here we investigate variation in reproductive traits of Triodanis perfoliata (Campanulaceae), a species that exhibits dimorphic cleistogamy, a condition in which individual plants have both closed (selfing: cleistogamous: CL) and open (selfing or outcrossing: chasmogamous: CH) flowers. Chasmogamous production is theorized to be more costly because CH flowers have a larger exposed surface area and thus are more likely to lose more water than CL flowers. We examine relationships between abiotic conditions (temperature, precipitation and soil characteristics) and variation in breeding systems across 14 widespread populations using ordinary least squares models. We found that a large proportion of breeding system variation was described by climate and soil variables (R2 = 0.65–0.92). These results support the hypothesis that variation in the environment drives variation in breeding system allocation. Our broad geographic analyses provide a framework for mechanistic studies of cleistogamy, and employ a novel approach for examining reproductive traits and environmental variation at large scales. Given that two major components of our models were temperature and precipitation, our study further emphasizes the potential for ongoing climate change to alter plant breeding systems.

Geography of plant breeding systems, agroclimatic similarity, and agricultural productivity: evidence from Nigeria

AbstractAgroclimatic conditions and agricultural research and development (R&D) including plant breeding activities by the public sector are some of the most significant exogenous factors in the agricultural sector. However, the effects of the interactions between these two sets of factors on agricultural productivity have not been studied widely in developing countries, despite potentially important implications on their plant breeding strategies. Using three‐wave panel data of agricultural households in Nigeria and spatial data on various agroclimatic parameters, we show that agricultural productivity and technical efficiency at the agricultural household level is significantly positively affected by the similarity of agroclimatic conditions between locations where agricultural households are located, and locations where major plant breeding institutes are located. These results hold after controlling for various socioeconomic characteristics of these households, including their physical distances to the breeding institutes. Findings are robust across parametric and nonparametric specifications such as Data Envelopment Method, and after addressing potential endogeneity of agroclimatic similarity and agricultural inputs variables in the production function. Productivity effects due to the locations of plant breeding institutes and resulting agroclimatic similarity can be potentially sizable given Nigeria's past productivity growth speed.

Transcriptome analysis of wheat seedling and spike tissues in the hybrid Jingmai 8 uncovered genes involved in heterosis.

Transcriptome analysis was carried out for wheat seedlings and spikes from hybrid Jingmai 8 and both inbred lines to unravel mechanisms underlying heterosis. Heterosis, known as one of the most successful strategies for increasing crop yield, has been widely exploited in plant breeding systems. Despite its great importance, the molecular mechanism underlying heterosis remains elusive. In the present study, RNA sequencing (RNA-seq) was performed on the seedling and spike tissues of the wheat (Triticum aestivum) hybrid Jingmai 8 (JM8) and its homozygous parents to unravel the underlying mechanisms of wheat heterosis. In total, 1686 and 2334 genes were identified as differentially expressed genes (DEGs) between the hybrid and the two inbred lines in seedling and spike tissues, respectively. Gene Ontology analysis revealed that DEGs from seedling tissues were significantly enriched in processes involved in photosynthesis and carbon fixation, and the majority of these DEGs expressed at a higher level in JM8 compared to both inbred lines. In addition, cell wall biogenesis and protein biosynthesis-related pathways were also significantly represented. These results confirmed that a combination of different pathways could contribute to heterosis. The DEGs between the hybrid and the two inbred progenitors from the spike tissues were significantly enriched in biological processes related to transcription, RNA biosynthesis and molecular function categories related to transcription factor activities. Furthermore, transcription factors such as NAC, ERF, and TIF-IIA were highly expressed in the hybrid JM8. These results may provide valuable insights into the molecular mechanisms underlying wheat heterosis.

Exotic plant species receive adequate pollinator service despite variable integration into plant-pollinator networks.

Both exotic and native plant species rely on insect pollinators for reproductive success, and yet few studies have evaluated whether and how exotic plant species receive services from native pollinators for successful reproduction in their introduced range. Plant species are expected to successfully reproduce in their exotic range if they have low reliance on animal pollinators or if they successfully integrate themselves into resident plant-pollinator networks. Here, we quantify the breeding system, network integration, and pollen limitation for ten focal exotic plant species in North America. Most exotic plant species relied on animal pollinators for reproduction, and these species varied in their network integration. However, plant reproduction was limited by pollen receipt for only one plant species. Our results demonstrate that even poorly integrated exotic plant species can still have high pollination service and high reproductive success. The comprehensive framework considered here provides a method to consider the contribution of plant breeding systems and the pollinator community to pollen limitation, and can be applied to future studies to provide a more synthetic understanding of the factors that determine reproductive success of exotic plant species.

Breeding system and pollination of Gesneria pauciflora (Gesneriaceae), a threatened Caribbean species

Knowledge of plant breeding systems may be critical to facilitate recovery of species considered at risk. Gesneria pauciflora is a threatened, rupiculous, and riverine species with floral-traits that suggest a hummingbird-pollination system. Because these habitat-pollinator conditions have been linked to pollinator-independent reproductive systems, we expected a breeding system that provides reproductive assurance. We assessed the breeding system and potential vulnerabilities during pollination phase using field observations and pollination experiments, to determine pollinator dependency and the existence of strategies for reproductive assurance. Gesneria pauciflora was pollinated by two hummingbird species but visitation rates were low, probably due to low nectar rewards. Fruit set and seed production were significantly higher in flowers when pollen was artificially delivered (self- and cross-pollination) compared to when it was not (control and autogamy), suggesting that reproduction is pollen-limited. Gesneria pauciflora is self-compatible, with some seeds produced via autonomous selfing without any effects of pollination mechanism on seed germination rates. Florivory by the native plume-moth Postplatyptilia caribica was observed, but its incidence was low (12%). Our findings are consistent with theory on the evolution of plant breeding systems on islands, and contribute to the understanding of the evolution of breeding systems in Caribbean gesneriads. Overall, data do not show immediate vulnerabilities to this listed species at the pollination phase, and autogamy may represent reproductive assurance counteracting unpredictable environmental factors that influence its reproduction. However, its capacity for selfing is small relative to other tubular Puerto Rican Gesneria which may explain its rare status.

Access to genes: linkages between genebanks and farmers’ seed systems

Genebanks conserve key resources for handling current and future challenges to food production and security. The role of genebanks has evolved from primarily serving plant breeders to include long-term biodiversity conservation and distribution to a wider user community. International policy frameworks stress the complementarity of ex situ and in situ conservation and management, but a dichotomy prevails in the public and scholarly agricultural development discourse. Here, we present a study of existing linkages between the two conservation and management approaches, their challenges and future options. First, we show that farmers, farmer organizations, and NGOs now comprise a considerable user group of genebank material, receiving at least 8% of the seed samples distributed from international genebanks in 2015, on par with the proportion distributed to the commercial seed sector. Second, we map and categorize approaches to introduce genebank material into farmers’ seed systems. Based on a survey, interviews and a literature review we categorize direct genebank-farmer linkages into six categories: (1) Reintroduction, (2) Emergency Seed Interventions, (3) Community Seed Banks, (4) Participatory Plant Breeding, (5) Variety Introduction, and (6) Integrative Seed System Approaches. We investigate the merits of these approaches as alternative and complementary pathways for enhancing farmers’ access to crop diversity. Finally, we discuss challenges related to scale, sustainability and legal frame conditions and point out opportunities to realize synergies to achieve the ultimate goal of the ex situ conservation agenda and the farmers’ rights agenda, namely to strengthen farmers’ access to suitable seeds.

Exploiting epigenetic variation for plant breeding.

Abstract In classical genetics and plant breeding, plant phenotypes are explained by genotype, environment and their interactions. Currently, the epigenetic component is recognized as another element functioning together with genetics and environment to determine phenotypic traits. Understanding the mechanism of epigenetics, the sources of epigenetic variation and epigenome editing will aid in incorporating the epigenetic component into plant breeding systems. The property of transgenerational inheritance of epigenetic marks, such as DNA methylation, will allow breeders to capture the underlying epigenetic alterations associated with phenotypic changes. Stably inherited epigenetic features can be subjected to artificial selection, which makes it possible to use epigenetic variation to improve agronomic traits and plant adaptation to environmental stress for crop improvement.

Dioecious plants are more precocious than cosexual plants: A comparative study of relative sizes at the onset of sexual reproduction in woody species.

The reproductive capacities of dioecious plant species may be limited by severe pollen limitation and narrow seed shadows for the two reasons. First, they are unable to self‐pollinate, and seed production occurs only with pollinator movement from males to females. Second, only 50% of the individuals in populations contribute to seed production. Despite these handicaps, dioecious plants maintain their populations in plant communities with cooccurring cosexual plants, and no substantial difference in population growth rates has been found between dioecious and cosexual plants. Hence, dioecious plants are thought to mitigate these disadvantages by adopting ecological traits, such as insect pollination, animal‐dispersed fleshy fruits, and precocious flowering. We studied the relationship between flowering and plant size in 30 woody species with different sex expressions, leaf habits, fruit types, and maximum plant sizes. The study site was located in an evergreen broad‐leaved forest on the island of Honshu, Japan. A phylogenetic linear regression model showed that dioecious species tended to mature at smaller sizes than did cosexual taxa. At the population level, given equal plant densities and reproductive efforts, the precocity of dioecious plants could serve as one of the factors that mitigate the limitations of pollen and seed‐shadow handicaps by increasing the density of reproductive individuals in the population. At the individual level, smaller size of onset of flowering may play a role in enhancing reproductive success over a lifetime by increasing reproductive opportunities. We discussed the possible effect of the relationship between precocity and some ecological traits of dioecious plants, such as small flowers pollinated by unspecialized insects, fleshy fruit dispersed by animals, and their preferential occurrence in the tropics and in island habitats. The universality of precocity among dioecious plants should be investigated in diverse plant communities. Such studies will increase our understanding of the evolution of plant breeding systems.

Sex‐biased oviposition by a nursery pollinator on a gynodioecious host plant: Implications for breeding system evolution and evolution of mutualism

Dioecy, a breeding system where individual plants are exclusively male or female, has evolved repeatedly. Extensive theory describes when dioecy should arise from hermaphroditism, frequently through gynodioecy, where females and hermaphrodites coexist, and when gynodioecy should be stable. Both pollinators and herbivores often prefer the pollen‐bearing sex, with sex‐specific fitness effects that can affect breeding system evolution. Nursery pollination, where adult insects pollinate flowers but their larvae feed on plant reproductive tissues, is a model for understanding mutualism evolution but could also yield insights into plant breeding system evolution. We studied a recently established nursery pollination interaction between native Hadena ectypa moths and introduced gynodioecious Silene vulgaris plants in North America to assess whether oviposition was biased toward females or hermaphrodites, which traits were associated with oviposition, and the effect of oviposition on host plant fitness. Oviposition was hermaphrodite‐biased and associated with deeper flowers and more stems. Sexual dimorphism in flower depth, a trait also associated with oviposition on the native host plant (Silene stellata), explained the hermaphrodite bias. Egg‐receiving plants experienced more fruit predation than plants that received no eggs, but relatively few fruits were lost, and egg receipt did not significantly alter total fruit production at the plant level. Oviposition did not enhance pollination; egg‐receiving flowers usually failed to expand and produce seeds. Together, our results suggest that H. ectypa oviposition does not exert a large fitness cost on host plants, sex‐biased interactions can emerge from preferences developed on a hermaphroditic host species, and new nursery pollination interactions can arise as negative or neutral rather than as mutualistic for the plant.

Self-compatibility is over-represented on islands.

Because establishing a new population often depends critically on finding mates, individuals capable of uniparental reproduction may have a colonization advantage. Accordingly, there should be an over-representation of colonizing species in which individuals can reproduce without a mate, particularly in isolated locales such as oceanic islands. Despite the intuitive appeal of this colonization filter hypothesis (known as Baker's law), more than six decades of analyses have yielded mixed findings. We assembled a dataset of island and mainland plant breeding systems, focusing on the presence or absence of self-incompatibility. Because this trait enforces outcrossing and is unlikely to re-evolve on short timescales if it is lost, breeding system is especially likely to reflect the colonization filter. We found significantly more self-compatible species on islands than mainlands across a sample of >1500 species from three widely distributed flowering plant families (Asteraceae, Brassicaceae and Solanaceae). Overall, 66% of island species were self-compatible, compared with 41% of mainland species. Our results demonstrate that the presence or absence of self-incompatibility has strong explanatory power for plant geographical patterns. Island floras around the world thus reflect the role of a key reproductive trait in filtering potential colonizing species in these three plant families.

Sexually-trimorphic interactions with colour polymorphism determine nectar quality in a herbaceous perennial

Amongst gynodioecious plant breeding systems, there can exist intermediate morphs with a reduction in their male function (i.e. reduced number of functional anthers). Along with this sexual trimorphism, plants can also show floral colour polymorphism. Such intricate mixtures of phenotypes within a species may have complex effects on floral rewards. Floral rewards are known to vary between sexually dimorphic species and to a lesser extent between colour morphs. However, the interactive effect of sexual trimorphism and colour polymorphism is unexplored. We measured nectar’s sugar content in the sexually trimorphic Geranium sylvaticum, a gynodioecious plant with a light/dark floral polymorphism. We found that nectar reward differed across genders and colour morphs. Results were not however consistent within the three genders; dark female and hermaphrodite flowers had higher sugar content than light morphs, whereas intermediate flowers did not. As expected, females and hermaphrodites had different nectar reward, with intermediate morphs being midway between the other genders. In intermediates, the sugar content was not related to the number of functional stamens. We show for the first time the existence of sex-specific differences between flower gender and colour morphs in nectar rewards. Our results demonstrate the importance of considering multiple and conflicting selection pressures to explain rewards.

Physiological and biochemical responses of hexaploid wheat cultivars to drought stress

Wheat is the most important cereal crop; it is staple diet for more than one third of the world population. Wheat production is influenced by several harsh environmental stresses that adversely affect its growth, metabolism and yield. Among them, Drought stress is the main factor limiting the productivity of wheat crop worldwide. Plants experience drought stress either when the water supply to roots becomes difficult or when the transpiration rate becomes very high. These two conditions often coincide under arid and semi-arid climates. Eighty percent area of Pakistan comes under arid and semi-arid region, so wheat productivity is adversely reduced in these areas due to lack of rain fall. Wheat yield under drought stress can be improved by several methods like conventional breeding, genetic transformation and marker assisted selection. For applying any of these methods, a close scans of morphological and physio-biochemical parameters are necessary. In the present study with 92 genotypes, a decrease of 35.57% for relative water content and 23.08% was observed for chlorophyll content in the stressed conditions. And an increase in metabolite level such as sugar (28.86%), SOD (4.53%) and canopy temperature (20.38%) was observed in moisture stress. Various genotypes have been identified which can be used further in plant breeding systems. Keywords: Wheat; Drought; Genotypes; Physio-biochemical; Metabolites http://dx.doi.org/10.19045/bspab.2016.50167

DevelopmentofGene-BasedSSRMarkersinWinged Bean(Psophocarpustetragonolobus(L.)DC.)for DiversityAssessment.

Winged bean (Psophocarpus tetragonolobus) is an herbaceous multipurpose legume grown in hot and humid countries as a pulse, vegetable (leaves and pods), or root tuber crop depending on local consumption preferences. In addition to its different nutrient-rich edible parts which could contribute to food and nutritional security, it is an efficient nitrogen fixer as a component of sustainable agricultural systems. Generating genetic resources and improved lines would help to accelerate the breeding improvement of this crop, as the lack of improved cultivars adapted to specific environments has been one of the limitations preventing wider use. A transcriptomic de novo assembly was constructed from four tissues: leaf, root, pod, and reproductive tissues from Malaysian accessions, comprising of 198,554 contigs with a N50 of 1462 bp. Of these, 138,958 (70.0%) could be annotated. Among 9682 genic simple sequence repeat (SSR) motifs identified (excluding monomer repeats), trinucleotide-repeats were the most abundant (4855), followed by di-nucleotide (4500) repeats. A total of 18 SSR markers targeting di- and tri-nucleotide repeats have been validated as polymorphic markers based on an initial assessment of nine genotypes originated from five countries. A cluster analysis revealed provisional clusters among this limited, yet diverse selection of germplasm. The developed assembly and validated genic SSRs in this study provide a foundation for a better understanding of the plant breeding system for the genetic improvement of winged bean.

Reproductive efficiency and photosynthetic pathway in seed plants

We aimed at determining whether C4 and CAM species had a higher reproductive efficiency than C3 species because of their higher water- and nitrogen-use efficiency. The resource-limitation hypothesis was also examined in the context of photosynthetic pathway. Reproductive efficiency was evaluated by measuring fruit set (fruit/flower ratio), seed set (seed/ovule ratio), and relative fecundity (the proportion of well-developed seed formed per ovule per infrutescence), along with seed abortion, and flower, fruit and seed biomass were evaluated. Photosynthetic pathway was determined according to literature, taxonomy, leaf anatomy and carbon isotopic composition (δ13C). Additionally, carbon and nitrogen content and nitrogen isotopic composition (δ15N) were determined. Plant life form and breeding system were considered. The traits of δ13C and δ15N were found to be positively correlated to fruit set, seed set and relative fecundity. The C4 species exhibited the highest values of fruit and seed set associated to the lowest biomass of flower, fruit, seed, and seed/fruit. The CAM species exhibited the highest values of flower and seed/fruit biomass and C3 species had the highest values of fruit and seed biomass. Reproductive efficiency was negatively related to the cost of reproductive structures in C3 species. The highest values of maximum relative fecundity were reached in CAM and C4 species under contrasting costs of reproductive structures: high values of fruits and seeds biomass in CAM species and low values of fruit and seed biomass in C4 species, suggesting that CAM species may reach high values of maximum fecundity irrespectively of fruit and seed cost. Patterns found in reproductive efficiency may be slightly modified according to life form and breeding system: fruit set was higher for annual than perennial herbs, which may be initially associated to the self-compatibility and autogamy of annual herbs. Fruit set increased from C3 to CAM species for annual herbs and decreased from C3 to CAM species for perennial herbs, indicating that C4 and CAM photosynthetic pathways could be associated with the increment of reproductive efficiency in annual species. Besides the traditionally acknowledged relationship with resistance to stressful environments, reproductive strategies of C4 and CAM plants could be also related to an increment in plant reproduction.

Morphology of Anemone sylvestris L. flower (Ranunculaceae)

Abstract During the monitoring of populations of Anemone sylvestris L. (Ranunculaceae), a protected species in Poland, we found that the seed set is impaired. The flower is considered an adaptation that has coevolved to achieve effective pollination and successful fertilization. Therefore we have focused on the morphological and anatomical characteristics of the flowers of A. sylvestris L. as a prelude to the study of the species’ pollination biology and plant breeding system. The large size of the flower (50.6 ± 16.4 mm in dimensions) and its bowl shape fulfil both the biotic pollination syndrome and the aerodynamic requirements for pollen dispersal and capture. The opening and closing of the perianth provide a shelter for beetles. The odourless perianth, absence of nectar, scarcity of pollen (approximately 200 000 pollen grains per flower) and its traits - small size (axis P = 18.52 ± 1.0 μm; E = 16.59 ± 0.9 μm), lack of balsam on the exine surface, starch accumulation in more than 95% of pollen grains correspond to the specialization in anemophily. The stigma is papillous, the dense hairs are situated between single carpels indicating adaptation to capturing dry pollen and specialization in the wind pollination syndrome. The flower of A. sylvestris is an example for an intermediate form between entomophily and anemophily, i.e. a secondary and more advanced feature among Ranunculaceae.

Seed exchange networks and food system resilience in the United States

Seed exchange is a multidimensional issue with social, political, economic, and agricultural implications. There is a growing concern about the increase of the food system’s vulnerability as a result of loss of agricultural biodiversity. Farmers’ ability to replant, exchange, and distribute saved seed is a way to minimize their dependence on commercial suppliers and thereby maintain control over farming practices. Seed saving is also crucial for conservation because the process of choosing, replanting, and exchanging seeds relies on and increases diversity on the farm and in communities. Seed exchange networks, formal and informal ways that farmers engage alongside institutional plant breeding systems, help to conserve agricultural, social, and cultural diversity and identity as well as enhance resilience against environmental and economic shocks. However, how to build resilient seed systems and move from the innovative but relatively isolated project activities of professionals and farmers to a situation where such approaches are scaled up and networked alongside formal and informal, national and international plant breeding mechanism are a concern. This paper examines grassroots seed exchange through seed libraries, the marketing of new varieties through seed companies, and hybrid civil society-business models to understand their financial and technical abilities as well as challenges they face. Seed exchange networks fulfill an important role in conservation of agricultural biodiversity and building community resilience through their work on breeding, exchange, and propagation of regionally adapted open-pollinated seeds as well as advocacy on seed sovereignty and education on seed saving.

Mechanism of Spontaneous Autogamy in the Allogamous Lepidopteran Orchid Gymnadenia Conopsea (L.) R. Br. (Orchidaceae)

Abstract Studies of plant breeding systems are particularly important when they involve facultative processes, which can be overlooked in natural conditions. This especially applies to species that are considered allogamous, due to their pollination syndrome and floral architecture. We examined the potential level and factors enabling or limiting spontaneous autogamy in three populations of the lepidopteran orchid Gymnadenia conopsea. Using a bagging experiment, we noted the stages of the anther thecae and the positions of the pollinaria at the five phenological stages of the flower, as well as the quantity of autogamously set fruits and the number of properly formed seeds. In the studied populations, autogamy represents an accidental character, with a maximum of 3.3% of fruits set spontaneously per analysed sample in a given population, and with seed numbers ranging from 29 to 354. This process is an environmentally dependent co-product of the mechanisms that enable a position appropriate for touching the stigma (bending of the caudicle) and increase male fitness (disintegration of the massulae), preceded by the gradual opening of the anther chambers. Autopollination of G. conopsea may occur in the flowers at various flowering stages (excluding the beginning of anthesis) at each position on the inflorescence.

The Robustness of Plant-Pollinator Assemblages: Linking Plant Interaction Patterns and Sensitivity to Pollinator Loss

Most flowering plants depend on pollinators to reproduce. Thus, evaluating the robustness of plant-pollinator assemblages to species loss is a major concern. How species interaction patterns are related to species sensitivity to partner loss may influence the robustness of plant-pollinator assemblages. In plants, both reproductive dependence on pollinators (breeding system) and dispersal ability may modulate plant sensitivity to pollinator loss. For instance, species with strong dependence (e.g. dioecious species) and low dispersal (e.g. seeds dispersed by gravity) may be the most sensitive to pollinator loss. We compared the interaction patterns of plants differing in dependence on pollinators and dispersal ability in a meta-dataset comprising 192 plant species from 13 plant-pollinator networks. In addition, network robustness was compared under different scenarios representing sequences of plant extinctions associated with plant sensitivity to pollinator loss. Species with different dependence on pollinators and dispersal ability showed similar levels of generalization. Although plants with low dispersal ability interacted with more generalized pollinators, low-dispersal plants with strong dependence on pollinators (i.e. the most sensitive to pollinator loss) interacted with more particular sets of pollinators (i.e. shared a low proportion of pollinators with other plants). Only two assemblages showed lower robustness under the scenario considering plant generalization, dependence on pollinators and dispersal ability than under the scenario where extinction sequences only depended on plant generalization (i.e. where higher generalization level was associated with lower probability of extinction). Overall, our results support the idea that species generalization and network topology may be good predictors of assemblage robustness to species loss, independently of plant dispersal ability and breeding system. In contrast, since ecological specialization among partners may increase the probability of disruption of interactions, the fact that the plants most sensitive to pollinator loss interacted with more particular pollinator assemblages suggest that the persistence of these plants and their pollinators might be highly compromised.

Patterns in floral traits and plant breeding systems on Southern Ocean Islands

The harsh climatic conditions and paucity of potential pollinators on Southern Ocean Islands (SOIs; latitude 46°S-55°S) lead to the expectation that anemophily or self-fertilization are the dominant modes of plant sexual reproduction. However, at least some species have showy inflorescences suggesting biotic pollination or dimorphic breeding systems necessitating cross-pollination. This study investigates whether anemophily and self-compatibility are common on SOIs, whether species or genera with these traits are more widespread or frequent at higher latitudes, and whether gender dimorphy is correlated with anemophily, as might occur if reliance on pollinators was a disadvantage. Of the 321 flowering plant species in the SOI region, 34.3 % possessed floral traits consistent with anemophily. Compatibility information was located for 94 potentially self-fertilizing species, of which 92.6 % were recorded as partially or fully self-compatible. Dioecy occurred in 7.1 % of species overall and up to 10.2 % of island floras, but has not clearly arisen in situ. Gynodioecy occurred in 3.4 % of species. The frequency of anemophily and gender dimorphy did not differ between the SOI flora and southern hemisphere temperate reference floras. At the species level, gender dimorphy was positively associated with fleshy fruit, but at the genus level it was associated with occurrence in New Zealand and a reduced regional distribution. Anemophily was more prevalent in genera occurring on subantarctic islands and the proportion of species with floral traits suggestive of biotic pollination was significantly higher on climatically milder, cool temperate islands. These results support the contention that reliance on biotic pollinators has constrained the distribution of species on SOIs; however, it is also clear that the reproductive biology of few SOI species has been studied in situ and many species likely employ a mixed mating strategy combining biotic pollination with self-fertilization.

Development of a genetic transformation system for distylous Turnera joelii (Passifloraceae) and characterization of a self-compatible mutant

Plants in the genus Turnera provide a useful system for investigating the molecular genetics of distyly and candidate genes involved in this plant breeding system have been proposed. We develop the first transformation system for the genus, using leaf explant tissue of Turnera joelii transformed using Agrobacterium tumefaciens harbouring the pGreen plasmid. Transgenic plants were successfully regenerated using a two growth-medium method and hygromycin resistance as the selectable marker. This should provide a system for testing the function of candidate genes for distyly. We obtained 19 transgenic plants and explore some of their characteristics. We find at least two instances where chromosomal abnormalities have occurred during the transformation process and observe reduced pollen fertility for seven of the transformants, likely evidence for somaclonal variation. We show that the transgenes inserted into two transgenic plants exhibit expected single gene segregation ratios, but find aberrant ratios for a third transgenic plant. The latter plant exhibits a mutant self-compatible phenotype, where self-compatibility is due to a defect in the incompatibility of its pollen. In crosses, the self-compatible transgenic plant shows marked departures from expected single locus ratios at the S-locus determining distyly, with an almost complete lack of transmission of the dominant S-allele. The plant appears to contain more than one copy of the inserted transgene based upon segregation ratios.