Genetic diversity revealed in the apomictic fruit species Garcinia mangostana L. (mangosteen)

The novel molecular marker technique Randomly Amplified DNA Fingerprinting (RAF) was used to survey genetic relationships between 37 accessions of the tropical fruit G. mangostana (mangosteen) and among 11 accessions from eight other Garcinia species. Although mangosteen is believed to reproduce exclusively through apomixis, our results show that considerable genetic diversity exists within G. mangostana and between other Garcinia species. Among the 37 G. mangostana accessions examined, nine different genotypes were identified which clustered into three distinct groups based on correspondence analysis (reciprocal averaging). For 26 (70%) of the accessions no marker variation was detected over 530 loci screened. A further eight (22%) accessions exhibited very low levels of variation (0.2-1%) suggesting at least one well conservedm angosteen genotype. The remaining three accessions (8%) showed extensive variation (22-31%) compared with the majority of accessions. The three mangosteen groups were 63-70% dissimilar to the other Garcinia species investigated. The genetic diversity identified in this research will assist in the conservation of Garcinia germplasm and provides a valuable framework for the genetic improvement of mangosteen.

Management of plant invasions mediated by frugivore interactions

1. Some of the most damaging invasive plants are dispersed by frugivores and this is an area of emerging importance in weed management. It highlights the need for practical information on how frugivores affect weed population dynamics and spread, how frugivore populations are affected by weeds and what management recommendations are available. 2. Fruit traits influence frugivore choice. Fruit size, the presence of an inedible peel, defensive chemistry, crop size and phenology may all be useful traits for consideration in screening and eradication programmes. By considering the effect of these traits on the probability, quality and quantity of seed dispersal, it may be possible to rank invasive species by their desirability to frugivores. Fruit traits can also be manipulated with biocontrol agents. 3. Functional groups of frugivores can be assembled according to broad species groupings, and further refined according to size, gape size, pre- and post-ingestion processing techniques and movement patterns, to predict dispersal and establishment patterns for plant introductions. 4. Landscape fragmentation can increase frugivore dispersal of invasives, as many invasive plants and dispersers readily use disturbed matrix environments and fragment edges. Dispersal to particular landscape features, such as perches and edges, can be manipulated to function as seed sinks if control measures are concentrated in these areas. 5.Where invasive plants comprise part of the diet of native frugivores, there may be a conservation conflict between control of the invasive and maintaining populations of the native frugivore, especially where other threats such as habitat destruction have reduced populations of native fruit species. 6. Synthesis and applications. Development of functional groups of frugivore-dispersed invasive plants and dispersers will enable us to develop predictions for novel dispersal interactions at both population and community scales. Increasingly sophisticated mechanistic seed dispersal models combined with spatially explicit simulations show much promise for providing weed managers with the information they need to develop strategies for surveying, eradicating and managing plant invasions. Possible conservation conflicts mean that understanding the nature of the invasive plant-frugivore interaction is essential for determining appropriate management.

Wolbachia infections of tephritid fruit flies: molecular evidence for five distinct strains in a single host species

Endosymbiotic bacteria of the genus Wolbachia are widespread among arthropods and can induce cytoplasmic incompatibility, thelytokous parthenogenesis, male-killing or feminization in their hosts. Here, we report phylogenetic relationships of Wolbachia in tephritid fruit flies based on wsp gene sequences. We also report, for the first time, five distinct strains of Wolbachia in Bactrocera ascita sp. B. Four of the five Wolbachia strains found in this species were in the same groups as those found in other tephritid fruit flies, suggesting possible horizontal transmission of Wolbachia from other fruit flies into B. ascita sp. B. The unreliability of wsp-specific group primers demonstrated in this study suggests that these primers might be useful only for preliminary identification of Wolbachia. Final determination of group affiliation needs to be verified with wsp sequence data.

Microsatellite markers for the pest fruit fly, Bactrocera papayae (Diptera : Tephritidae) and other Bactrocera species

The dorsalis complex contains some of the most economically important fruit fly pests of the Asia-Pacific regions, including Bactrocera dorsalis, Bactrocera papayae and Bactrocera carambolae. These species are morphologically indistinct and genetically very similar. We describe the development of 12 microsatellite markers isolated from a representative of the dorsalis complex, B. papayae. We show the potential utility of the B. papayae microsatellites and a set of microsatellites isolated from Bactrocera tryoni as population and species markers for the dorsalis complex.

Host preference and host suitability in an egg-pupal fruit fly parasitoid, Fopius arisanus (Sonan) (Hym., Braconidae)

The relative oviposition rate of the parasitoid Fopius arisanus (Sonan) was investigated across three frugivorous tephritid species, Bactrocera tryoni Froggart, Bactrocera jarvisi (Tryon) and Bactrocera cucumis French. Choice and no-choice tests were both used. The suitability of these three species for sustaining larval development and survival to the adult stage was also assessed. Fopius arisanus parasitized all three tephritid species. regardless of the method of exposure, but showed stronger preference for B. tryoni and B. jarvisi over B. cucumis. Superparasitism was extremely rare. Successful development of F. arisanus varied across host species. Bactrocera tryoni yielded significantly more parasitoids than B. jarvisi, but no wasps emerged from B. cucumis puparia. Tests were set up in replicated trials. but results were not homogeneous across trials. We discuss the host relationships of F. arisanus with reference to this variation and in relation to host suitability for larval development.

Olfaction in the Queensland fruit fly, Bactrocera tryoni. I: Identification of olfactory receptor neuron types responding to environmental odors

The electroantennogram method was used to investigate the number of distinct olfactory receptor neuron types responding to a range of behaviorally active volatile chemicals in gravid Queensland fruit flies, Bactrocera tryoni. Three receptor neuron types were identified. One type responds to methyl butyrate, 2-butanone, farnesene, and carbon dioxide; a second to ethanol; and a third to n-butyric acid and ammonia. The receptor neuron type responding to methyl butyrate, 2-butanone, farnesene, and carbon dioxide consists of three subtypes. The presence of a limited number of receptor neuron types responding to a diverse set of chemicals and the reception of carbon dioxide by a receptor neuron type that responds to other odorants are novel aspects of the peripheral olfactory discrimination process.

Olfaction in the Queensland fruit fly, Bactrocera tryoni. II: Response spectra and temporal encoding characteristics of the carbon dioxide receptors

Single-unit electrophysiology was used to record the nerve impulses from the carbon dioxide receptors of female Queensland fruit flies, Bactrocera tryoni. The receptors responded to stimulation in a phasic-tonic manner and also had a period of inhibition of the nerve impulses after the end of stimulation, at high stimulus intensities. The cell responding to carbon dioxide was presented with a range of environmental odorants and found to respond to methyl butyrate and 2-butanone. The coding characteristics of the carbon dioxide cell and the ability to detect other odorants are discussed, with particular reference to the known behavior of the fly.

Floral structure, breeding system and fruit-set in the threatened sub-shrub Tetratheca juncea Smith (Tremandraceae)

Tetratheca juncea Smith (Tremandraceae) has undergone a range contraction of approx. 50 km in the last 100 years and is now listed as a vulnerable sub-shrub restricted to the central and north coast regions of New South Wales, Australia. There are approx. 250 populations in a 110 km north-south distribution and populations are usually small with fewer than 50 plants/clumps. The reproductive ecology of the species was studied to determine why seed-set is reportedly rare. Flowers are bisexual, odourless and nectarless. Flowers are presented dependentally and there are eight stamens recurved around the pistil. Anthers are poricidal, contain viable pollen and basally contain a deep-red tapetal fluid that is slightly oily. Thus flowers are presented for buzz pollinators, although none were observed at flowers during our study. The species was found to be facultatively xenogamous with only one in 50 glasshouse flowers setting seed autogamously, i.e. without pollinator assistance. Field studies revealed fertile fruit in 24 populations but production varied significantly across sites from exceedingly low (0.6 fruits per plant clump) to low (17 fruits per plant clump). Fruit-set ranged from 0 to 65%, suggesting that pollen vectors exist or that autogamy levels in the field are variable and higher than glasshouse results. Fruit production did not vary with population size, although in three of the five populations in the south-west region more than twice as much fruit was produced as in populations elsewhere. A moderately strong relationship between foliage volume and fruit : flower ratios suggests that bigger plants may be more attractive than smaller plants to pollinators. A review of Tetratheca pollination ecology revealed that several species are poorly fecund and pollinators are rare. The habitat requirements for Tetratheca, a genus of many rare and threatened species, is discussed. (C) 2003 Annals of Botany Company.

Factors supporting the non-persistence of fruit fly populations in South Australia

For purposes of interstate and international fruit trade, it is necessary to demonstrate that in areas in which fruit fly species have not previously established permanent populations, but which are subject to introductions of fruit flies from outside the area, the introduced population once detected, has not become established. In this paper, we apply methodology suggested mainly by Carey (1991, 1995) to introductions of Mediterranean fruit fly (Medfly), Ceratitis capitata Weid., and Queensland fruit fly (QFF) Bactrocera tryoni Froggatt (Diptera: Tephritidae) to South Australia, a state in which these species do not occur naturally and in which introductions, once detected, are actively treated. By analysing historical data associated with fruit fly outbreaks in South Australia, we demonstrate that: (i) fruit flies occur seasonally, as would occur in established populations, except there is no evidence of the critical spring generation of either species; (ii) there is no evidence of increasing frequency of outbreaks, trapped flies or larval occurrences over 29 years; (iii) there is no evidence of decreasing time between catches of adult flies as the years progress; (iv) there is no decrease in the mean number of years between outbreaks in the same locations; (v) there is no statistically significant recurrence of outbreaks in the same locations in successive years; (vi) there is no evidence of spread of outbreaks outwards from a central location; (vii) the likelihood of outbreaks in a city or town is related to the size of the human population; (viii) introduction pathways by road from Western Australia (for Medfly) and eastern Australia (for QFF) are shown to exist and to illegally or accidentally carry considerable amounts of fruit into South Australia; and (ix) there was no association between the numbers of either Queensland fruit fly or Medfly and the spatial pattern of either loquat or cumquat trees as sources of larval food in spring. This analysis supports the hypothesis that most fruit fly outbreaks in South Australia have been the result of separate introductions of infested fruit by vehicular traffic and that most of the resultant fly outbreaks were detected and died out within a few weeks of the application of eradication procedures. An alternative hypothesis, that populations of fruit flies are established in South Australia at below detectable levels, is impossible to disprove with conventional technology, but the likelihood of it being true is minimised by our analysis. Both hypotheses could be tested soon with newly developed genetic techniques.

Fruit processing, seed viability and dormancy mechanisms of Persoonia sericea A. Cunn. ex R. Br. and P-virgata R. Br. (Proteaceae)

The morphology of the fruit and difficulties with fruit processing impose major limitations to germination of Persoonia sericea and P. virgata. The mesocarp must be removed without harming the embryo. Fermentation of fruit or manual removal of the mesocarp was effective but digestion in 32% hydrochloric acid (HCl) completely inhibited germination. The endocarp is extremely hard and therefore very difficult and time consuming to remove without damaging the seeds. The most efficient method was cracking the endocarp with pliers, followed by manual removal of seeds. Germination was completely inhibited unless at least half of the endocarp was removed. Microbial contamination of the fruit and seeds was controlled by disinfestation and germination of the seed under aseptic conditions. The results suggest that dormancy in these species is primarily due to physical restriction of the embryo by the hard endocarp.

Detection of fruit and the selection of primate visual pigments for color vision

Primates have X chromosome genes for cone photopigments with sensitivity maxima from 535 to 562 nm. Old World monkeys and apes (catarrhines) and the New World ( platyrrhine) genus Alouatta have separate genes for 535-nm ( medium wavelength; M) and 562-nm ( long wavelength; L) pigments. These pigments, together with a 425-nm ( short wavelength) pigment, permit trichromatic color vision. Other platyrrhines and prosimians have a single X chromosome gene but often with alleles for two or three M/L photopigments. Consequently, heterozygote females are trichromats, but males and homozygote females are dichromats. The criteria that affect the evolution of M/L alleles and maintain genetic polymorphism remain a puzzle, but selection for finding food may be important. We compare different types of color vision for detecting more than 100 plant species consumed by tamarins ( Saguinus spp.) in Peru. There is evidence that both frequency-dependent selection on homozygotes and heterozygote advantage favor M/L polymorphism and that trichromatic color vision is most advantageous in dim light. Also, whereas the 562-nm allele is present in all species, the occurrence of 535- to 556-nm alleles varies between species. This variation probably arises because trichromatic color vision favors widely separated pigments and equal frequencies of 535/543- and 562-nm alleles, whereas in dichromats, long-wavelength pigment alleles are fitter.

Spiroacetal biosynthesis: ()-1,7-dioxaspiro[5.5]undecane in Bactrocera cacuminata and Bactrocera oleae (olive fruit fly)

[GRAPHICS] A biosynthetic scheme rationalizing the formation of (+/-)-1,7-dioxaspiro[5.5]undecane (5) in the fruit fly species Bactrocera cacuminata and Bactrocera oleae (olive fruit fly) is presented. Incorporation studies with deuterium-labeled keto aldehyde (10), 1,5-nonanediol (11), and 1,5,9-nonanetriol (12), and our previous finding that both oxygen atoms of 5 originate from dioxygen, are strongly evidentiary. The racemic condition of the natural spiroacetal 5 is accounted for, and inter alia, it is demonstrated that dihydropyran (18) is not an important intermediate en route to 5.

Development of a DNA-based method for detection and identification of Phytophthora species

Phytophthora diseases cause major losses to agricultural and horticultural production in Australia and worldwide. Most Phytophthora diseases are soilborne and difficult to control, making disease prevention an important component of many disease management strategies. Detection and identification of the causal agent, therefore, is an essential part of effective disease management. This paper describes the development and validation of a DNA-based diagnostic assay that can detect and identify 27 different Phytophthora species. We have designed PCR primers that are specific to the genus Phytophthora. The resulting amplicon after PCR is subjected to digestion by restriction enzymes to yield a specific restriction pattern or fingerprint unique to each species. The restriction patterns are compared with a key comprising restriction patterns of type specimens or representative isolates of 27 different Phytophthora species. A number of fundamental issues, such as genetic diversity within and among species which underpin the development and validation of DNA-based diagnostic assays, are addressed in this paper.

Discovery of genes associated with fruit ripening in Carica papaya using expressed sequence tags

To identify genes involved in papaya fruit ripening, a total of 1171 expressed sequence tags (ESTs) were generated from randomly selected clones of two independent fruit cDNA libraries derived from yellow and red-fleshed fruit varieties. The most abundant sequences encoded: chitinase, 1-aminocyclopropane- 1-carboxylic acid (ACC) oxidase, catalase and methionine synthase, respectively. DNA sequence comparisons identified ESTs with significant similarity to genes associated with fruit softening, aroma and colour biosynthesis. Putative cell wall hydrolases, cell membrane hydrolases, and ethylene synthesis and regulation sequences were identified with predicted roles in fruit softening. Expressed papaya genes associated with fruit aroma included isoprenoid biosynthesis and shikimic acid pathway genes and proteins associated with acyl lipid catabolism. Putative fruit colour genes were identified due to their similarity with carotenoid and chlorophyll biosynthesis genes from other plant species. © 2005 Elsevier Ireland Ltd. All rights reserved.