Pollination biology, breeding system and reproductive success of Adhatoda vasica,an important medicinal plant

Adhatoda vasica Nees.(Acanthaceae) is an important and widely used medicinal plant. The flowers last for 3–5 days, they are protandrous and pass through three distinct phases: male, bisexual and female. Two species of carpenter bees, Xylocopa verticalis and Xylocopa sp. are the effective pollinators. Pollen grains are deposited on the dorsal surface of the thorax during Xylocopa visit to the flowers in the male phase, and the stigma rubs the pollen-coated thorax and is pollinated when the bees visit the flowers in bisexual and female phases. There is a high level of geitonogamy. Pollination efficiency under field conditions is high (95%). However, fruit set is poor (6%). The species is self-incompatible. None of the self-pollinated flowers sets fruits, but over 50% of the cross-pollinated flowers sets fruits. The results indicate that protandry does not prevent self pollination, but reduces interference in export and import of pollen. Although the flowers have adapted well to achieve a high level of pollination, reproductive success in terms of fruit set is low, largely due to the limitation of compatible pollen

Reproductive assurance through autogamous self-pollination across diverse sexual and breeding systems

Pollination becomes a constraint when conspecific plants and/or their pollinators become scarce. Many plant species have evolved autogamous self-pollination as a means of reproductive assurance (RA) under pollination-uncertain environments. So far RA has been studied and discussed largely with reference to self-compatible species producing bisexual flowers. RA seems to have evolved across all other sexual and breeding systems - monoecy, dioecy and self-incompatibility (SI). Both monoecy and dioecy produce bisexual flowers (andro/gyno-monoecy, andro/gynodioecy and polygamous conditions) which may provide RA. Similarly, most of the SI species are leaky and do set some seeds upon self-pollination. This phenomenon termed 'partial self-compatibility' is quite common and does provide RA in SI species. Although dioecy and SI have evolved as obligate outbreeding systems, they seem to have reached an evolutionary dead end because of the constraints for outcross pollination. In the light of habitat destruction leading to a reduction in the diversity and density of native pollinators, it is likely that many of the obligate outbreeders tend to shift to mixed mating system in the coming decades. Similarly, obligate mutualism in which each plant species is dependent on one animal species for pollination also seems to have reached a dead end and the trend is to abandon such obligate mutualism as a survival strategy. In the absence of such a change, obligate out breeders and those with highly specialized pollination system are likely to become endangered or even extinct

Fertilization in Flowering Plants 2. Selection of the Male Partner is the Prerogative of the Maternal Parent

After the pollen grain reaches the stigma through outsourced agents (pollinators), the next step before fertilization is to select the right type of pollen. Similar to a marriage in human beings, flowering plants also have evolved elaborate screening process to select the right pollen grains and to reject the wrong ones. Even after initial screening for the right pollen, the pistil imposes a tough competition amongst them, comparable to a swayamvara of Indian mythology, to select the best available pollen. Flowering plants have evolved into a matriarchal society. The selection of the male partner is totally the prerogative of the mother (pistil); the boy (pollen grain) and the girl (ovule) has no say in this selection

Pollination biology of large cardamom (Amomum subulatum)

Amomum subulatum Roxb. (family Zingiberaceae) is the large cardamom of commerce cultivated in tropical wet evergreen forests of the Eastern Himalayas of India, Nepal and Bhutan. This study seeks to identify floral visitors and pollinators, examine floral adaptations for pollination and evaluate pollination efficiency. Studies were carried out in two flowering seasons (2005, 2006) in a 6-ha plantation located adjacent to a degraded reserve forest in the Sikkim part of the Himalayas. Only two flower visitor species, a bumble-bee (Bombus haemorrhoidalis Smith) and a honey bee species (Apis cerana F.) were recorded. The bumble-bee was the effective and only pollinator, but A. ceranawas the pollen robber. Major flower adaptations for pollination by the bumble-bee are the length of the nectar tube, which is not accessible to short-tongued bees and a narrow passage in the fresh flower between the anther–stigma column and the labellum. The narrow passage forces the bumble-bee to push the anther–stigma column to enter the flower, which brings the body of the bumble-bee in contact with the anther and the stigma, and effects pollination. A. cerana does not come in contact with the stigma during pollen foraging and hence is unable to bring about pollination. Thus, structural features of the flower of A. subulatum differentiate the pollinator and the pollen robber. Pollination efficiency in the plantation was low due to the low population density of wild native pollinator, B. haemorrhoidalis

Pollination biology of Aristolochia tagala, a rare species of medicinal importance

Floral phenology, pollination biology and breeding system were studied in Aristolochia tagala Cham (Aristolochiaceae) grown under ex situ conditions. The flower exhibits structural features typical of fly-trap mechanism described for other Aristolochia species. Flowers show pronounced protogyny. Stigmas are receptive at anthesis and remain so for 24 h. Anthers dehisce 45– 48 h after anthesis by which time stigma receptivity is lost. Chironomid fly (Diptera) is the pollinator. Attracted by the odour and colour of the flower, the flies enter it and are detained in the chamber of the perianthtube (where the anthers and stigma are located) for nearly 50 h. Their escape is prevented by the presence of dense downward-pointing hairs in the perianth tube. The nectaries provide food to the insects. Following anther dehiscence, the thorax of the flies becomes loaded with sticky pollen grains. Hairs on the inner wall of the perianth tube wither and facilitate the exit of the flies. When a fly carrying the pollen load enters a fresh flower, it brings about pollination. Manual pollinations showed that the species permits geitonogamous pollination. The percentage of fruit set in manually pollinated flowers is higher than that resulting from open pollination, confirming that pollination is a limitation for fruit set in the ex situ-grown population. Nevertheless, fruit and seed set is sufficiently high for ex situ conservation purposes

Cryopreservation of oil palm pollen

Approximately 5 g of oil palm (Elaeis guineensis) pollen was stored in liquid nitrogen from March 1998 to April 2006. Pollen grains that were cryopreserved for up to 8 years retained as high as 54±1.72% viability (compared with 62±4.33% before storage) and 49±1.2% in vitro germinability (compared with 52±2.08% before storage). Results indicate the feasibility of cryogenically storing oil palm pollen for long periods without any significant loss in viability and germinability

Genetic architecture and evolution of the S locus supergene in Primula vulgaris

Darwin’s studies on heterostyly in Primula described two floral morphs, pin and thrum, with reciprocal anther and stigma heights that promote insect-mediated cross-pollination. This key innovation evolved independently in several angiosperm families. Subsequent studies on heterostyly in Primula contributed to the foundation of modern genetic theory and the neo-Darwinian synthesis. The established genetic model for Primula heterostyly involves a diallelic S locus comprising several genes, with rare recombination events that result in self-fertile homostyle flowers with anthers and stigma at the same height. Here we reveal the S locus supergene as a tightly-linked cluster of thrum-specific genes that are absent in pins. We show that thrums are hemizygous not heterozygous for the S locus, which suggests that homostyles do not arise by recombination between S locus haplotypes as previously proposed. Duplication of a floral homeotic gene 51.7 MYA, followed by its neofunctionalisation, created the current S locus assemblage which led to floral heteromorphy in Primula. Our findings provide new insights into the structure, function and evolution of this archetypal supergene

Successful wide hybridization and introgression breeding in a diverse set of common peppers (Capsicum annuum) using different cultivated ají (C. baccatum) accessions as donor parents

[EN] Capsicum baccatum, commonly known as aji, has been reported as a source of variation for many different traits to improve common pepper (C. annuum), one of the most important vegetables in the world. However, strong interspecific hybridization barriers exist between them. A comparative study of two wide hybridization approaches for introgressing C. baccatum genes into C. annuum was performed: i) genetic bridge (GB) using C. chinense and C. frutescens as bridge species; and, ii) direct cross between C. annuum and C. baccatum combined with in vitro embryo rescue (ER). A diverse and representative collection of 18 accessions from four cultivated species of Capsicum was used, including C. annuum (12), C. baccatum (3), C. chinense (2), and C. frutescens (1). More than 5000 crosses were made and over 1000 embryos were rescued in the present study. C. chinense performed as a good bridge species between C. annuum and C. baccatum, with the best results being obtained with the cross combination [C. baccatum (female) x C. chinense (male)] (female) x C. annuum (male), while C. frutescens gave poor results as bridge species due to strong prezygotic and postzygotic barriers. Virus-like-syndrome or dwarfism was observed in F-1 hybrids when both C. chinense and C. frutescens were used as female parents. Regarding the ER strategy, the best response was found in C. annuum (female) x C. baccatum (male) crosses. First backcrosses to C. annuum (BC(1)s) were obtained according to the crossing scheme [C. annuum (female) x C. baccatum (male)] (female) x C. annuum (male) using ER. Advantages and disadvantages of each strategy are discussed in relation to their application to breeding programmes. These results provide breeders with useful practical information for the regular utilization of the C. baccatum gene pool in C. annuum breeding.Juan P. Manzur thanks Universitat Politecnica de Valencia for a research predoctoral grant (2011-S2-4264, programa para la formacion de personal investigador). Authors are grateful to Centro Inv. Agr. Mabegondo, S. Larregla from NEIKER, P.W. Bosland from NMSU and the Consejos Reguladores of IGP Pimiento Asado del Bierzo, DOP Pimenton de Murcia, and IGP Piquillo de Lodosa for providing us with seeds from Arnoia, Guindilla de Ibarra, Numex, Bierzo, Bola and Piquillo, respectively.Manzur Poblete, JPA.; Fita, A.; Prohens Tomás, J.; Rodríguez Burruezo, A. (2015). Successful wide hybridization and introgression breeding in a diverse set of common peppers (Capsicum annuum) using different cultivated ají (C. baccatum) accessions as donor parents. PLoS ONE. 10(12). https://doi.org/10.1371/journal.pone.0144142Se0144142101

Ant-pollination: A Rare and Enigmatic Mutualism

Mutualism refers to interactions between species that result in reciprocal benefits. There are several mutualistic interactions between plants and animals. These mutualisms are in the form of a biological barter in which the resources of one species are exchanged with the services of the other. Mutual interactions are common between plants and ants (Beattie, 1985; Rico-Gray and Oliveira, 2007). Myrmecophily, particularly in species of Acacia, is one such mutualism in which plants possess structural adaptations that provide ants with food and/or shelter. In exchange, ants protect plants from herbivores. Ants also act as seed dispersal agents. Many plant species produce fruits or seeds with special ant attractants – arils or elaiosomes. Ants carry such fruits and seeds to their nest. After consuming the attractants, the seeds/fruits are discarded with other wastes either in the nest or outside the nest entrance