997 resultados para Cross-pollination


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DNA- and RNA-based polymerase chain reaction (PCR) systems were used with Cacao swollen shoot virus (CSSV) primers designed from conserved regions of the six published genomic sequences of CSSV to investigate whether the virus is transmissible from infected trees through cross-pollination to seeds and seedlings. Pollen was harvested from CSSV infected cocoa trees and used to cross-pollinate flowers of healthy cocoa trees (recipient parents) to generate enough cocoa seeds for the PCR screening. Adequate precautions were taken to avoid cross-contamination during duplicated DNA extractions and only PCR results accompanied by effective positive and negative controls were scored. Results from the PCR analyses showed that samples of cocoa pod husk, mesocarp and seed tissues (testa, cotyledon and embryo) from the cross-pollinations were PCR negative for CSSV DNA. Sequential DNA samples from new leaves of seedlings resulting from the cross-pollinated trees were consistently PCR negative for presence of portions of CSSV DNA for over 36 months after germination. A reverse transcription-PCR analysis performed on the seedlings showed negative results, indicating absence of functional CSSV RNA transcripts in the seedlings. None of the seedlings exhibited symptoms characteristic of the CSSV disease, and all infectivity tests on the seedlings were also negative. Following these results, the study concluded that although CSSV DNA was detected in pollen from CSSV infected trees, there was no evidence of pollen transmission of the virus through cross-pollination from infected cocoa parents to healthy cocoa trees. Keywords:badnavirus;CSSV;PCR;pollen;seed transmission;Theobroma cacao

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DNA- and RNA-based polymerase chain reaction (PCR) systems were used with Cacao swollen shoot virus (CSSV) primers designed from conserved regions of the six published genomic sequences of CSSV to investigate whether the virus is transmissible from infected trees through cross-pollination to seeds and seedlings. Pollen was harvested from CSSV infected cocoa trees and used to cross-pollinate flowers of healthy cocoa trees (recipient parents) to generate enough cocoa seeds for the PCR screening. Adequate precautions were taken to avoid cross-contamination during duplicated DNA extractions and only PCR results accompanied by effective positive and negative controls were scored. Results from the PCR analyses showed that samples of cocoa pod husk, mesocarp and seed tissues (testa, cotyledon and embryo) from the cross-pollinations were PCR negative for CSSV DNA. Sequential DNA samples from new leaves of seedlings resulting from the cross-pollinated trees were consistently PCR negative for presence of portions of CSSV DNA for over 36 months after germination. A reverse transcription-PCR analysis performed on the seedlings showed negative results, indicating absence of functional CSSV RNA transcripts in the seedlings. None of the seedlings exhibited symptoms characteristic of the CSSV disease, and all infectivity tests on the seedlings were also negative. Following these results, the study concluded that although CSSV DNA was detected in pollen from CSSV infected trees, there was no evidence of pollen transmission of the virus through cross-pollination from infected cocoa parents to healthy cocoa trees.

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The lack of pear-compatible rootstocks in Brazil calls for the application of classical genetic techniques. Therefore, in order to obtain select suitable material, the search for genetic segregation must be continuous, being used as alternative scion cultivars. This study aims to assess fruit set, number of seeds, fruit weight and fruit diameter according to crosses between pear cultivars. The trial was carried out from September 2008 to February 2009 in a commercial orchard in the city of Vacaria/RS, Brazil. For the pollination process, pollen was extracted from flowers at full-white stage in the same orchard. The cultivars used were 'Packham's Triumph' and 'Clapps Favorite'. The crossings were defined as: open pollination; selfpollination of 'Packham's Triumph' and 'Packham's Triumph' × 'Clapps Favorite'. The pollinations were done manually in flowers at full-white stage, which were opened, emasculated and then pollinated. Each pollinated flower was then isolated with a fine nylon bag. Open pollination and cross pollination between 'Packham's Triumph' × 'Clapps Favorite' provided higher fruit set (17 and 18%, respectively). Fruit weight and diameter did not differ between treatments. Open pollination provided fruits with a higher number of seeds.

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Relationships among floral biology, floral micromorphology and pollinator behaviour in bird-pollinated orchids are important issues to understand the evolution of the huge flower diversity within Orchidaceae. We aimed to investigate floral mechanisms underlying the interaction with pollinators in two hummingbird-pollinated orchids occurring in the Atlantic forest. We assessed floral biology, nectar traits, nectary and column micromorphologies, breeding systems and pollinators. In both species, nectar is secreted by lip calli through spaces between the medial lamellar surfaces of epidermal cells. Such form of floral nectar secretion has not been previously described. Both species present functional protandry and are self-compatible yet pollinator-dependent. Fruit sets in hand-pollination experiments were more than twice those under natural conditions, evidencing pollen limitation. The absence of fruit set in interspecific crosses suggests the existence of post-pollination barriers between these synchronopatric species. In Elleanthus brasiliensis, fruits resulting from cross-pollination and natural conditions were heavier than those resulting from self-pollination, suggesting advantages to cross-pollination. Hummingbirds pollinated both species, which share at least one pollinator species. Species differences in floral morphologies led to distinct pollination mechanisms. In E. brasiliensis, attachment of pollinaria to the hummingbird bill occurs through a lever apparatus formed by an appendage in the column, another novelty to the knowledge of orchids. In E. crinipes, pollinaria attachment occurs by simple contact with the bill during insertion into the flower tube, which fits tightly around the bill. The novelties described here illustrate the overlooked richness in ecology and morphophysiology in Orchidaceae. This article is protected by copyright. All rights reserved.

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The present study was carried out in Northeastern Region of Brazil, in order to investigate the use of stingless bee Melipona subnitida Ducke in the pollination of greenhouse sweet pepper (Capsicum annuum L.). Treatments of hand cross-pollination, hand self-pollination, pollination by bees and restricted pollination were performed. Results showed that despite sweet pepper flowers are considered autogamous, this crop benefits from pollination by M. subnitida, producing fruits significantly heavier and wider, containing a greater number of seeds and of better quality (lower percentage of malformed fruits) than self-pollinated sweet pepper. Thus, M. subnitida can be considered an efficient pollinator of greenhouse sweet pepper.

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The objective of this work was to evaluate the floral biology and pollination requirements of seeded and seedless mini watermelon varieties, and to determine the best varieties to cultivate under protected environment. Three seedless (HA-5106, HA-5158, and HA-5161) and two seeded (Minipol and Polimore) genotypes were tested. Flowers were monitored from the pre-anthesis stage to senescence, and fruit quality was also evaluated. The evaluated treatments were hand-geitonogamous pollination (MG), cross-pollination with pollen from the Polimore variety (MCP), cross-pollination with pollen from the Minipol variety (MCM), and restricted pollination. All varieties had monoecious plants with diclinous flowers, and the stigmas remained receptive throughout anthesis. Fruit set rates of 84.62% (MG), 61.54% (MCP), 48% (MCM), and 0% (restricted) were obtained for seeded varieties, but of 0% (MG), 76.36% (MCP), 82.69% (MCM), and 0% (restricted) for seedless varieties. Fruits did not differ in quality among treatments within each genotype. Therefore, all the studied varieties require a pollination agent and diploid pollen for fruit set to occur, regardless of the donor variety; and Minipol or Polimore with HA-5106 or HA-5158 are the varieties recommended for cultivation in protected environment.

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The pollination ecology and breeding systems of Tabebuia aurea (Manso) Benth. & Hook., and T. ochracea (Cham.) Standl. were investigated in an area of cerrado vegetation in the Federal District of Brazil. These species occur sympatrically, flower massively and synchronously for a month, during the dry season (July to September). Both have diurnal anthesis, with similar floral structures, a yellow tubular corolla and produce nectar. Fourteen species of bees visited both Tabebuia species, but, only three Centris species and Bombus morio, were considered potential pollinators, because of their high frequency on the flowers and their efficiency in carrying pollen. Tests on the breeding systems of T. aurea and T. ochracea demonstrated that boths species are self-incompatible, with late-acting self-incompatibility. The proportion of fruit set from cross pollination (T. aurea 17.2% and T. ochracea 12.3%) in both species was low considering the great number of flowers displayed. This suggests a lack of maternal resources for fruit-set. The great amount of seeds per fruit (about 92 in T. aurea and 285 in T. ochracea) may represent an investment of maternal resources allocated on higher quality of fertilized ovules.

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Jacaranda copaia (Aubl.) D. Don is a pioneer tree widespread in the Brazilian Amazon, usually found colonizing forest gaps and altered areas, and the forest fragment edges. This study investigated aspects of the floral biology, breeding system and pollinators of J. copaia trees. Flowering lasts from August to November, during the low rainfall period extending up to four weeks per tree and 3-4 months for the population as a whole, characterizing a cornucopia flowering pattern. The fruit set ends in the beginning of the rainy season, with wind dispersed winged seeds. Fruit set from open pollination was 1.06% (n = 6,932). Hand pollination using self-pollen (n = 2,099) did not set fruits. Cross-pollination resulted in 6.54% fruit set (n = 2,524), representing six times more than the natural pollination rate (1.06%, n = 6,932). Flowers excluded from insect visitation (automatic self-pollination) did not set fruits (n = 5,372). Pollen tube growth down to ovary was detected under fluorescence microcoscopy in cross-pollinated and selfed pistils. The species is an obligate allogamous plant, with late-acting self-incompatibility system. Approximately 40 species of native bees visited the flowers, but the main pollinators were medium-sized solitary bees as Euglossa and Centris species due to the compatibility between their body sizes with the corolla tube, direct contact with the reproductive structures and high frequency of visits.

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This study aimed to characterize the reproductive system of Passiflora capsularis L. and P. rubra L. In vivo controlled pollinations, in vitro pollen germination and pollen-ovule (P:O) ratio evaluation were conducted. In self-pollination, intraspecific and interspecific pollination, P. capsularis showed means of 62.5, 68.7 and 48.4% of fertilized flowers, while in P. rubra, the averages were 67.2, 62.5 and 46.9%, respectively. For in vitro germination, 52.2% of P. capsularis pollen grains germinated while in P. rubra, the percentage was 64.4. The P:O ratio was 22.4 for P. capsularis, and 27.4 for P. rubra, which included them in the category of obligatory autogamous. Passiflora capsularis and P. rubra can reproduce both by self-pollination and cross-pollination, and crossings between the two species succeeded though the success rate was lower than 50%. The characteristics of the reproductive system of both species allow the use of greater range of options on breeding methods for production of ornamental Passiflora plants.

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Adenocalymma bracteatum is a shrub of dense foliage and yellow flowers, easily found on grasslands areas in Central Brazil. The aim of this study was to determine the reproductive biology and the flower visitors of A. bracteatum in a pasture area nearby Ivinhema city, MS (Brazil). The flowering peak occurs in winter. The flower reflects ultraviolet light. Anthesis begins at 6:30h, and pollen and nectar are the resources to visitors. We captured 1,038 floral visitors. The bees Apis mellifera (L.), Trigona sp., Trigona spinipes (Fabricius), (Hymenoptera: Apoidea) and the ant Cephalotes sp. (Hymenoptera: Formicidae) were the main visitors. The reproductive tests indicate that A. bracteatum is self compatible, justifying its expansion in altered environments; however, the largest reproductive success was dependant on cross-pollination and self-pollination, evidencing the pollinators importance. Adenocalymma bracteatum presents melittophilous syndrome and bumblebees were the main pollinators in the area. The correlations observed between the climatic variables and the main pollinator species were low or medium.

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Background and aims Late-acting self-incompatibility (LSI). in which selfed flowers fail to form fruits despite apparently successful growth of the pollen tubes to the ovules, is a contentious and still poorly understood phenomenon. Some studies have indicated pollen tube-pistil interactions, and major gene control. Others favour an early acting inbreeding depression explanation.Methods Experimental pollinations, including selfs (in a subsample of which the style was cut before pollen tubes reached the ovary), chase self/cross-pollinations, crosses, and mixed self/cross-pollinations were used to study floral/pistil longevity and effect on fruit set and seed yield in two Ceiba species known to have LSI.Results Self-pollinations, including those with a cut style, had extended floral longevity compared with unpollinated flowers. Chase pollinations in which cross-pollen was applied up to 3 h after selfing set fruits, but with reduced seed set compared with crosses. Those with cross-pollen applied at 4 and 8 h after self-pollination all failed to set fruits. Flowers subjected to 1 : 1 and 2 : 1 self/cross-pollinations all produced fruits but again with a significantly lower seed set compared with crosses.Conclusions Extended floral longevity initiated with self-pollen tubes growing in the style indicates some kind of pollen tube-pistil interaction. Fruit set only in chase pollinations up to 3 h implies that self-pollen tubes either grow more slowly in the style or penetrate ovules more slowly on arrival at the ovary compared with cross-tubes. This agrees with previous observations indicating that the incidence of penetrated ovules is initially lower in selfed compared with crossed pistils. However, the low seed yield from mixed pollinations indicates that self- and cross-pollen tubes arrive at the ovary and penetrate ovules more or less simultaneously. Possible explanations for these discordant results are discussed. (C) 2004 Annals of Botany Company.

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Eschweilera nana is pollinated by a guild of pollinators consisting of mostly bees. Effective pollinators are large bees able to force their way into the closed androecium to access nectar. The morphology of the flowers diminishes self pollination and promotes cross-pollination. Although many pollinators make diurnal visits to the flowers, fruit set was very low in comparison with the number of flowers produced. Breeding system tests yielded only two fruits, one produced by xenogamy and another one in the control test. The results of this study are consistent with studies of other Cerrado plants pollinated by guilds of insects and support the conclusion of other pollination studies of Lecythidaceae that fruit set is low in comparison with the high numbers of flowers produced. © 2013 The New York Botanical Garden.

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Jackfruit (Artocarpus heterophyllus Lam.) is a multi-purpose fruit tree, native to tropical Asia. It was introduced to South Florida in the early 1900s but has had little commercial importance. In recent years, there has been an increased interest in jackfruit as a commercial crop in South Florida, but there has been little scientific investigation conducted. The pollination mechanism was not clearly understood. This study focused on jackfruit breeding using 'Dang Rasimi' and 'Cheena' cultivars. Controlled hand-pollinations revealed that both cultivars were not apomictic. Both cultivars set fruit with self-pollination, but seed set and many fruit characters such as size, flesh percentage and edible percentage were greatly enhanced with cross-pollination. I conclude that jackfruit are outbreeding plants. Tests for pollen dispersal by wind were inconclusive. A variety of insects were collected, but few had a role in pollination. My results suggest that jackfruit are likely to have insect-assisted wind pollination in South Florida. ^

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The reproductive biology, reward production and pollination mechanism of Trichocentrum pumilum were studied in a gallery forest in the interior of the State of Sao Paulo, southeast Brazil. The floral visitors and pollination mechanism were recorded, and experimental pollinations were carried out in order to determine the breeding system of this species. Trichocentrum pumilum blooms in spring. Each paniculate inflorescence bears an average of 85 flowers that present a central yellow callus and finger-like trichomes on the lateral lobes of the lip. A lipoidal substance is produced and stored among these trichomes. In the studied population, T. pumilum is exclusively visited and pollinated by two bee species (Tetrapedia diversipes and Lophopedia nigrispinis). Pollinaria are deposited on mouthparts of bees during collection of the lipoidal substance from the lateral lobes of the labellum. Trichocentrum pumilum is self-incompatible and pollinator-limited. Natural fruit set was low (9%, compared to 45% in experimentally cross-pollinated flowers). Potentially viable seed exceed 97% in fruits obtained through cross-pollination and in natural conditions (open pollination).