Ascidians (Urochordate) are hermaphroditic marine invertebrates that release sperm and eggs to the surrounding seawater. However, several ascidians, including Ciona intestinalis and Halocynthia roretzi, show strict self-sterility due to a self/nonself-recognition mechanism in the interaction between sperm and the vitelline coat (VC) of the eggs. We have previously reported that sperm intracellular Ca2+ level drastically increased immediately after sperm binding to the VC of self eggs but not nonself eggs in C. intestinalis type A, which was potently inhibited by lowering the external Ca2+ concentration, suggesting that sperm Ca2+ influx occurs after sperm self-recognition on the VC. Here, we investigated whether self-sterility was abolished by lowering the external Ca2+ concentration in C. intestinalis. The results showed that the block to self-fertilization was removed by low-Ca2+ (∼1 mM) seawater without decreasing the fertilization rate. Such an effect was not observed with Mg2+ or K+. These results led us to conclude that a low-Ca2+ environment is sufficient to block the self-recognition signal upon fertilization. As low-Ca2+ seawater showed no effect on H. roretzi self-sterility, we propose that the mechanism of self-sterility in Ciona must be distinctive from that in Halocynthia.

Niger (Guizotia abyssinica, L.) is a desirable oilseed crop for birdseed, especially for finches (Spinus spp.) because of its high ratio of unsaturated to saturated fatty acids and relatively high oil content. In 2012, phenotypic traits, seed oil and fatty acid content measurements were made on 14 plant introductions (PIs) from the United States Department of Agriculture germplasm collection. The PIs originated in Ethiopia (ten), India (three) and USA (one). The phenotypic traits analysed included seed/plant, branches/plant, capitula/plant1, average seed/capitulum and plant height. After initial assessments of the 14 PIs, three were selected for use as parents to produce two one-way and two two-way F1 crosses for the purpose of evaluating self-incompatibility (SI). Parent and F1 progeny seeds were planted in a greenhouse and transplanted to a field site at the East Tennessee Research and Education Center (2012, 2013 and 2014). Comparisons from 2012 showed seed oil of the 14 PIs ranging from 32.9 to 37.9% (PI 508076 (Ethiopia) and PI 509436 (India), respectively). Major fatty acids included stearic, palmitic, oleic and linoleic; with linoleic acid in highest amount. PI508079 (Ethiopia) had the best combination of seed yield, seed oil and linoleic acid content. Over 2013 and 2014, SI ranged from 91.1 to 100.0%. W6 18860 (USA) had the most self-compatibility, and the F1 plants generated from crosses between W6 18860 and other plants tended to be self-compatible when the former was used as a pollen recipient. The results obtained from this study should be useful for niger breeding and production purposes.

The floral biology and pollination ecology of durian, Durio zibethinus, were determined in eight semi-wild trees in mixed-fruit orchards in southern Thailand during April-May 2003 and 2005. Flowers open fully at 16h00–16h30 and most androecia drop around 01h00. Anthers dehisce at 19h30–20h00 when the stigmata are already receptive. In a series of pollination experiments, fruit was set in all treatments within 10 d. The greatest pollination success occurred after hand-crossed (76.6%), open (54.4%) and emasculation pollination (53.3%). Consistently, hand-crossed (12.2%), emasculation (8.7%) and open pollination (5.1%) yielded a substantial fruit set 2 mo after the pollination experiments. Very low pollination success in facilitated autogamy suggests that most durian trees are highly self incompatible. No mature fruit was found after insect pollination and automatic autogamy. Fruit bats, especially Eonycteris spelaea, are the major pollinators of this durian although the giant honey bee (Apis dorsata) was the most frequent visitor to the flowers. Bats visited durian flowers at the rate of 26.1 (SD = 20.7) visits per inflorescence per night. Since this semi-wild durian depends on fruit bats as its pollinator, protecting fruit bat populations and their roosts is vital for the production of the durian fruit crop.

As a member of the tribe Brassiceae, Eruca sativa, although a minor crop worldwide, is considered a valuable genetic resource for cabbage, rapeseed and other Brassica crops. Self-incompatibility (SI) in Brassica has been extensively studied, but information on SI in E. sativa is limited. Of six chemicals used to treat the stigmas to overcome SI in five E. sativa lines, gibberellin was the most effective. As gibberellin is well known for its ability to break dormancy and to promote cell elongation, its effectiveness may help to understand the mechanisms of SI. Urea and ammonium sulphate were also effective. These two chemicals are known to affect protein stability, which may help explain their effects on SI. Although table salt has been reported as being effective in overcoming SI in B. rapa, B. oleracea and B. napu, it was not effective in E. sativa. Sucrose and alcohol also had negligible effect. There was significant variation among the genotypes in SI intensity and response to chemicals, but the genotype–chemical interaction was not significant. The data presented in this paper add to our understanding of SI in E. sativa and may lead to a better use of this genetic resource.

Compatible pollination of Brassica napus necessitates pollen hydration, pollen germination and growth of the pollen tube through the loosened walls of stigmatic papillar cells, whereas self-incompatible (SI) pollinations fail at one of these stages. Analyses of the early stages of pollination show that at high (but not low) relative humidities, both compatible and SI pollen hydrates, but SI germination is reduced and the rare pollen tubes generally fail to penetrate the papillar walls, although there is some wall loosening. Inside the papillae, both compatible and SI interactions may induce the formation of callose, but there is no evidence for a major accumulation of cytoplasm or secretory vesicles in the vicinity of the pollen tubes and neither microtubule nor F-actin patterns re-arrange in this zone. These observations indicate that the source of the wall-loosening enzymes is probably the pollen tube or pollen coat, and that the common cellular responses of plants to attempted invasions have become suppressed in the papilla–pollen tube interaction.