Marine plant harvest in Portugal

This work brings together the scattered information on marine plant harvests and the colloid extraction industry in Portugal, as an initial contribution to the improvement of resource management. The first phase of exploitation of marine plant resources started prior to the 14th century, with the gathering and sale of storm-tossed seaweeds for fertilizer. The harvest of seagrasses and algae at Ria de Aveiro was of great economic importance. The second phase of resource exploitation began with the wider scale harvest of agarophyte species for colloid extraction. Portugal is at present the third largest harvester of the agarophytes Gelidium and Pterocladia (2500 t annually), and it is the fifth largest agar producer (350 t annually). Other colloid-producing species, including Chondrus crispus and Mastocarpus stellatus, are also harvested for export. The total agarophyte landings, agar production and income from agar exports is far below the maximum levels attained in the early 1970s. The status of stocks in each different harvest zone on the continental coast and the Azores is examined. Although there is an effective management structure for the Portuguese marine plant resource, research is needed to provide a sound biological basis for management. author for correspondence     

Bacterial parasite of a plant nematode: morphology and ultrastructure.

The life cycle of a bacterial endoparasite of the plant-parasitic nematode Meloidogyne incognita was examined by scanning and transmission electron microscopy. The infective stage begins with the attachment of an endospore to the surface of the nematode. A germ tube then penetrates the cuticle, and mycelil colonies form in the pseudocoelom. Sporulation is initiated when terminal cells of the mycelium enlarge to form sporangia. A septum within each sporangium divides the forespore from the basal or parasporal portion of the cell. The forespore becomes enclosed by several laminar coats. The parasporal cell remains attached to the forespore and forms the parasporal microfibers. After the newly formed spores are released into the soil, these microfibers apparently enable a mature spore to attach to the nematode. These results indicate that the endoparasite is a procaryotic organism having structural features that are more common to members of Actinomycetales and to the bacterium Pasteuria ramosa than to the sporozoans or to the family Bacillaceae, as previous investigatios have concluded.     

Genetic stability in a population of a plant pathogenic fungus over time

Collections of the plant pathogenic fungus Mycosphaerella graminicola were made from the same field of wheat over a 3-year period. The field was planted with small plots containing four varieties of wheat grown in pure stand and in all possible two-, three- and four-way mixtures. In each year, the wheat field was recolonized by a local source of inoculum of unknown origin. Allele frequencies at 10 RFLP loci were compared at two different times within a growing season and over the 3-year period. No significant differences in allele frequencies were found for any of the RFLP loci over any of the time periods. DNA fingerprints were used to identify clones produced by asexual reproduction. Genotypic diversity based on the frequency of each clone was compared for each collection. No significant changes in genotypic diversity were found within a year or between years. Identical genotypes were found in the field at different times within a season, but no clones were conserved between years. No clone existed in a high frequency in any year, suggesting that selection for particular asexual lineages was weak. The founding population each year probably originated from wind-borne ascospores of the teleomorph, which may exist as an indigenous population on alternative hosts, such as Poa annua (annual bluegrass).     

Notes on plant communities of Spitsbergen

17 plant associations belonging to 9 alliances from Spitsbergen are discussed; 7 associations, 2 alliances and 1 order are described as new. The percentage of diploids and polyploids in individual plant communities and their relation to ecology is examined.     

Population structure of a vector‐borne plant parasite

Parasites are among the most diverse groups of life on Earth, yet complex natural histories often preclude studies of their speciation processes. The biology of parasitic plants facilitates in situ collection of data on both genetic structure and the mechanisms responsible for that structure. Here, we studied the role of mating, dispersal and establishment in host race formation of a parasitic plant. We investigated the population genetics of a vector‐borne desert mistletoe (Phoradendron californicum) across two legume host tree species (Senegalia greggii and Prosopis velutina) in the Sonoran desert using microsatellites. Consistent with host race formation, we found strong host‐associated genetic structure in sympatry, little genetic variation due to geographic site and weak isolation by distance. We hypothesize that genetic differentiation results from differences in the timing of mistletoe flowering by host species, as we found initial flowering date of individual mistletoes correlated with genetic ancestry. Hybrids with intermediate ancestry were detected genetically. Individuals likely resulting from recent, successful establishment events following dispersal between the host species were detected at frequencies similar to hybrids between host races. Therefore, barriers to gene flow between the host races may have been stronger at mating than at dispersal. We also found higher inbreeding and within‐host individual relatedness values for mistletoes on the more rare and isolated host species (S. greggii). Our study spanned spatial scales to address how interactions with both vectors and hosts influence parasitic plant structure with implications for parasite virulence evolution and speciation.     

Specificity in the interaction between an epibiotic clavicipitalean fungus and its convolvulaceous host in a fungus/plant symbiotum

Ipomoea asarifolia and Turbina corymbosa (Convolvulaceae) are associated with epibiotic clavicipitalean fungi responsible for the presence of ergoline alkaloids in these plants. Experimentally generated plants devoid of these fungi were inoculated with different epibiotic and endophytic fungi resulting in a necrotic or commensal situation. A symbiotum of host plant and its respective fungus was best established by integration of the fungus into the morphological differentiation of the host plant. This led us to suppose that secretory glands on the leaf surface of the host plant may play an essential role in ergoline alkaloid biosynthesis which takes place in the epibiotic fungus.Key words: ergoline alkaloids, ipomoea, turbina, convolvulaceae, claviceps, balansia, clavicipitaceae, penicillium, plant-fungus symbiotum     

Biosynthesis of jasmonic acid in a plant pathogenic fungus, Lasiodiplodia theobromae

Jasmonic acid (JA) is a plant hormone that plays an important role in a wide variety of plant physiological processes. The plant pathogenic fungus, Lasiodiplodia theobromae also produces JA; however, its biosynthesis in this fungus has yet to be explored. Administration of [1-(13)C] and [2-(13)C] NaOAc into L. theobromae established that JA in this fungus originates from a fatty acid synthetic pathway. The methyl ester of 12-oxo-phytodienoic acid (OPDA) was detected in the culture extracts of L. theobromae by GC-MS analysis. This finding indicates the presence of OPDA (a known intermediate of JA biosynthesis in plants) in L. theobromae. (2)H NMR spectroscopic data of JA produced by L. theobromae with the incorporation of [9,10,12,13,15,16-(2)H(6)] linolenic acid showed that five deuterium atoms remained intact. In plants, this is speculated to arise from JA being produced by the octadecanoid pathway. However, the observed stereoselectivity of the cyclopentenone olefin reduction in L. theobromae was opposite to that observed in plants. These data suggest that JA biosynthesis in L. theobromae is similar to that in plants, but differing in the facial selectivity of the enone reduction.     

Definition of tissue-specific and general requirements for plant infection in a phytopathogenic fungus

Although plant diseases are usually characterized by the part of the plant that is affected (e.g., leaf spots, root rots, wilts), surprisingly little is known about the factors that condition the ability of pathogens to colonize different plant tissues. Here we demonstrate that the leaf blast pathogen Magnaporthe grisea also can infect plant roots, and we exploit this finding to distinguish tissue-specific and general requirements for plant infection. Tests of a M. grisea mutant collection identified some mutants that were defective specifically in infection of either leaves or roots, and others such as the map kinase mutant pmk1 that were generally defective in pathogenicity. Conservation of a functional PMK1-related MAP kinase in the root pathogen Gaeumannomyces graminis was also demonstrated. Exploitation of the ability of M. grisea to infect distinct plant tissues thus represents a powerful tool for the comprehensive dissection of genetic determinants of tissue specificity and global requirements for plant infection.     

Notes on the Laboulbeniales (Ascomycota) parasitic on Diptera from Portugal and other countries

Eighteen species of Stigmatomyces are reported for the first time from continental Portugal and/or from the Azores. These are Stigmatomyces asteiae W. Rossi et Cesari, Stigmatomyces athyroglossae W. Rossi et Cesari, Stigmatomycescanzonerii W. Rossi et Cesari, Stigmatomyces ceratophorus Whisler, Stigmatomyces constrictus Thaxt., Stigmatomyces crassicollis Thaxt., Stigmatomyces divergatus Thaxt., Stigmatomyces discocerinae Thaxt., Stigmatomyces ensinae Thaxt., Stigmatomyces cf. ephydrae L. Mercier et R. A. Poiss., Stigmatomycesgeomyzae W. Rossi et Cesari, Stigmatomyces limnophorae Thaxt., Stigmatomyces majewskii H. L. Dainat, Manier et Balazuc, Stigmatomyces papuanus Thaxt., Stigmatomycesplatensis Speg., Stigmatomyces ptylomyiae Thaxt. and Stigmatomyces purpureus Thaxt., Stigmatomyces rugosus Thaxt. New records of these species are also reported from Australia, Canada, Canary Islands (Spain), Costa Rica, Cuba, Ecuador, Finland, Germany, Great Britain, Greece, Kenya, Hungary, Israel, Kyrgyzstan, Lebanon, Morocco, Saudi Arabia, Sierra Leone, Taiwan, Thailand, Turkey, Uganda, United Arab Emirates, USA, Yemen and Zimbabwe. The new records increase, sometimes considerably, information about distribution of these parasites. Two synonymies are also established: Stigmatomyces autriquei Balazuc = Stigmatomyces ensinae Thaxt.; Stigmatomyces psilopae Thaxt. var. camarguensis H. L. Dainat et J. Dainat = S. rugosus Thaxt.     

Pscroph,a parasitic plant EST database enriched for parasite associated transcripts

Background  

Parasitic plants in the Orobanchaceae develop invasive root haustoria upon contact with host roots or root factors. The development of haustoria can be visually monitored and is rapid, highly synchronous, and strongly dependent on host factor exposure; therefore it provides a tractable system for studying chemical communications between roots of different plants.     

Interaction of a host plant and its holoparasite: effects of previous selection by the parasite

If parasites decrease the fitness of their hosts one could expect selection for host traits (e.g. resistance and tolerance) that decrease the negative effects of parasitic infection. To study selection caused by parasitism, we used a novel study system: we grew host plants (Urtica dioica) that originated from previously parasitized and unparasitized natural populations (four of each) with or without a holoparasitic plant (Cuscuta europaea). Infectivity of the parasite (i.e. qualitative resistance of the host) did not differ between the two host types. Parasites grown with hosts from parasitized populations had lower performance than parasites grown with hosts from unparasitized populations, indicating host resistance in terms of parasite’s performance (i.e. quantitative resistance). However, our results suggest that the tolerance of parasitic infection was lower in hosts from parasitized populations compared with hosts from unparasitized populations as indicated by the lower above‐ground vegetative biomass of the infected host plants from previously parasitized populations.