Endophytic fungi of grasses protect other plants from aphid herbivory

Microbial plant symbionts are widely spread in nature changing the way their hosts interact with their environment. Neotyphodium fungal endophytes (Clavicipitaceae) are grass symbionts known by their production of alkaloids, toxic for herbivores. Here, we hypothesized that endophytes confer associational protection to non-host plants and change emission of host volatile-compounds. In an outdoor mesocosm experiment, we examined aphid infestation on Trifolium repens plants, in response to Neotyphodium occultans presence in neighbouring Lolium multiflorum. Contrasting levels of Rhizobium were generated in T. repens plants considering that symbiosis with N₂-fixers would influence herbivore abundance. Aphid infestation increased responding to symbiotic status of T. repens plants, when surrounded by non-symbiotic L. multiflorum plants. Endophytes modified the volatile imprints of L. multiflorum plants measured by an electronic nose, suggesting a potential mechanism to benefit neighbours. This associational protection constitutes a new mutualism trait of grass-endophyte symbiosis, becoming a non-private benefit available to other community partners.     

Galactosidases in cultivated and wild peas

The level of α- and β-galactosidase was followed in the cotyledons and embryos of germinating seeds of Pisum sativum and P. elatius. α-Galactosidase is preformed in the cotyledons but its activity increases during germination in the embryos. β-Galactosidase activity in embryos increases during germination but shows little change in cotyledons. The possible function of α- and β-galactosidase is discussed.     

Molecular diversity and physical mapping of 5S rDNA in wild and cultivated oat grasses (Poaceae: Aveneae).

5S rDNA repeats studied in five genera of Aveneae have lengths between 285 and 329 bp (Avena sativa, Avena macrostachya, 26 species of Helictotrichon, Pseudarrhenatherum longifolium, Lagurus ovatus, and Trisetum spicatum). In only a single species (Helictotrichon aetolicum) an additional repeat of 456 bp occurs infrequently. Variation is largely due to insertions or deletions in the nontranscribed spacer as determined from sequences of 163 independent clones. The 5S gene of the Aveneae studied is conserved in length and sequence except for Helictotrichon bromoides and Helictotrichon marginatum in which duplications occur at two different sites. This new type of duplication and all duplications reported to date in 5S genes of angiosperms are shown to center on defined palindromic sequences. The "uncommon" 5S gene sequences detected in some Aveneae are not necessarily nonfunctional as pseudogenes because the essential features of the internal control region are maintained even after such duplication events. In each instance such gene sequences have spacers with unmodified structure, indicating that change in gene sequence is not necessarily coupled with change in adjacent spacers. The value of 5S spacer sequences for genomic identifications in Aveneae is exemplified in A. macrostachya (perennial), A. sativa (annual), and several diploid taxa of the genus Helictotrichon.     

Endophytic fungi from Melia azedarach

A collection of endophytic fungi was obtained from living apparently symptomless roots, stems, leaves and fruits of Melia azedarach. This is an exotic tree introduced into Brazil from Asia and is a producer of insecticidal compounds. It grows very well and is apparently resistant to many pathogens. Each segment from the plant was sampled during two periods. A total of 55 fungal isolates were recovered. Hyphomycetes were more prevalent than Ascomycetes, Coelomycetes and Basidiomycetes. The genera Aspergillus and Penicillium were the most common in the plant.     

Oviposition acceptance and larval development of Chilo partellus stemborers in drought‐stressed wild and cultivated grasses of East Africa

Maternal host choices during oviposition by herbivorous insects determine the fitness of their offspring and may be influenced by environmental changes that can alter host‐plant quality. This is of particular relevance to ‘push‐pull’ cropping systems where host preferences are exploited to manage insect pest populations. We tested how drought stress in maize and companion plants that are used in these systems affect oviposition preference, larval feeding, and development of the spotted stemborer, Chilo partellus Swinhoe (Lepidoptera: Crambidae). Five host species were tested (all Poaceae): maize (Zea mays L.), Napier grass (Pennisetum purpureum Schumach), signal grass [Brachiaria brizantha (A. Rich) Stapf], Brachiaria cv. ‘Mulato’, and molasses grass [Melinis minutiflora (Beauv.)]. Under drought stress, maize experienced as much oviposition as control unstressed maize in choice and no‐choice experiments. Similarly, larval leaf damage was not significantly different in drought‐stressed vs. unstressed maize. In contrast, oviposition occurred less on drought‐stressed than on unstressed Napier and signal grass. Oviposition acceptance and leaf damage remained low in both drought‐stressed and unstressed molasses grass and Mulato. Larval survival and development remained high in drought‐stressed maize, but not in Napier, signal, and molasses grass and Mulato, where survival and development were low in both drought‐stressed and unstressed plants. Our results indicate that herbivore responses to drought‐stressed plants depend on the plant species and that drought stress can change host preference and acceptance rankings. In particular, trap‐crops such as Napier grass may not divert oviposition from the main maize crop under drought stress conditions.     

Occurrence of Peronospora sparsa (P. rubi) on cultivated and wild Rubus species in Finland and Sweden

An outbreak of a dryberry disease caused by Peronospora sparsa (syn. P. rubi) occurred in plantations of arctic bramble (Rubus arcticus subsp. arcticus) in Finland in the middle of 1990s. The disease persists and is most severe in cool and rainy summers. The disease has not been encountered in northern Sweden where cultivars (R. arcticus nothosubsp. stellarcticus) different from those in Finland are used. The occurrence of P. sparsa in wild Rubus spp. is virtually unknown in both areas and it is not known whether they constitute a potential infection source. Therefore, the aim of this study was to investigate the occurrence of P. sparsa on wild Rubus spp. growing in the vicinity of cultivations of arctic bramble. Symptomatic plants were sampled in 1997–1999. P. sparsa was detected using a light microscope, preceded by incubation of the sample in vitro if necessary, and by a polymerase chain reaction (PCR) based method. Plants of cultivated R. arcticus subsp. arcticus were commonly infected by P. sparsa in Finland. P. sparsa was also found on the cultivated R. arcticus nothosubsp. stellarcticus in Finland and Sweden. However, the infected plants of the cultivars of nothosubsp. stellarcticus seemed to be much less damaged than the cultivars of subsp. arcticus. Plants infected with P. sparsa were found in the populations of wild R. arcticus subsp. arcticus in both countries, and in cloudberry (R. chamaemorus) in natural habitats in Finland. In addition, P. sparsa was detected on specimens of R. arcticus subsp. arcticus (collected in 1966–1985) and R. chamaemorus (collected in 1899–1981) in Finnish herbaria. The samples of R. idaeus and R. saxatilis collected from the field in this study or investigated in the herbaria were not infected with P. sparsa. These data show that P. sparsa has not recently invaded Finland but has become an economically significant pathogen during the rapid expansion of cultivation of the apparently sensitive clones of arctic bramble.     

Endophytic yeast fungi in plant storage tissues

It was found that plant storage tissues (fleshy sugar-containing fruits, subsurface metamorphically altered plant organs (storage roots, tubers, etc.), and starch-containing seed lobes) nearly always contain yeasts that are able to actively reproduce in these tissues causing no visible damage. Within storage tissues, yeast cells were detected both in the intercellular space and inside plant cells. In the tissues of fleshy fruits, endophytic yeasts are represented by the same species as epiphytic ones; cryptococci of the order Filobasidiales and ascomycetes belonging to the genera Hanseniaspora and Metschnikowia are predominant. In subsurface plant organs, red pigmented basidiomycetous yeasts of the genus Rhodotorula prevail. Selective growth of representatives of one species, Candida railenensis, is typical of starch-containing storage tissues of seeds. The results obtained change the established notion of the distributional patterns of yeast fungi in natural habitats and suggest that internal storage tissues of plants can be considered as a new interesting model for studies of coevolving plant-microbial associations.     

Calystegines in wild and cultivated Erythroxylum species

Calystegines were identified in the genus Erythroxylum for the first time. Erythroxylum novogranatense var. novogranatense, a species cultivated for cocaine production, contained 0.2% total calystegines in dry leaves. Forty six Erythroxylum herbarium species consisting mostly of leaf tissue were analysed for calystegines, and 38 were found positive. Calystegines were compared qualitatively and quantitatively between individual Erythroxylum species. Calystegines A(3) and B(2) were the major calystegines in most species. Total calystegine content reached up to 0.32% dry mass. The simultaneous occurrence of calystegines, cocaine, other alkaloids of a 3alpha-hydroxy- or 3beta-hydroxytropane structure together with nicotine supports the concept of common biosynthetic steps of these alkaloids in Erythroxylum. The present results are the basis for further investigations of the phylogenetic origin of tropane alkaloid biosynthesis in the taxonomically remote families Solanaceae and Erythroxylaceae.     

Endophytic fungi from Amomum siamense.

Endophytic fungi were isolated from apparently healthy organs of the wild ginger Amomum siamense Criab.. including leaves, pseudostems, and rhizomes, collected from two sites in Doi Suthep-Pui National Park, Thailand. Endophytes were relatively common with an isolate prevalence of 70%-83% at the two sites sampled in the wet and dry seasons. The endophyte assemblages from the two sites were diverse and comprised 7 Ascomycetes and 26 mitosporic fungi. Colletotrichum "gloeosporioides" (Penz.) Penz. & Sacc. in Penz., Glomerella spp., xylariaceous fungi, and Phomopsis spp. were consistently dominant as endophytes on Amomum siamense, but many rare species and mycelia sterilia were also recorded. There was no significant difference between the number of isolates recovered from leaves containing vein tissues and those containing intervein tissues, independent of leaf age. Most taxa showed a preference for either leaf tissue or pseudostems. Two new Ascomycetes species. Gaeumannomyces amomi and Leiosphaerella amomi, were discovered from leaves and rhizomes, respectively, and four species of Pyricularia, including three new species, were isolated from leaves.     

Collecting cultivated and wild Cucurbits in Mexico

The authors spent approximately 5 weeks in Mexico (October 13–November 15, 1979) collecting Cucurbitaceae in 5 areas: 1) Tampico- Valles- Ocampo; 2) San Luis Potosi; 3) Celaya- Queretaro; 4) Veracruz; 5) Zacatecas- Durango- Mazatlan. A few supplemental collections were made in the vicinity of Tapachula, Chiapas. A grand total of 183Cucurbita collections was made, distributed as follows:C. pepo-49;C. moschata-47;C. mixta- 41;C. ficifolia-11;C. foetidissima-13;Cucurbita sp. wild, unidentified- 22. A few collections were made in the following genera:Sechium-4;Lagenaria-2;Sicana-1;Momordica-4;Sicyos-2;Cucumis melo-2;C. anguria-1. The ecological distribution of the 4 cultivated species is reported and discussed. Seed of these materials was divided equally between the participating countries, and will be made available to interested plant breeders.     

禾本科植物内生真菌资源及其物种多样性

植物内生真菌是当代微生物资源研究的一个热门话题,对禾本科植物内生真菌资源研究进行了总结。与冷季型禾本科植物共生的麦角菌科epichlo内生真菌是目前的研究重点,包括偶尔在宿主植物体表形成子座的Epichlo属真菌和几乎完全不形成症状的Neotyphodium属真菌。具体介绍该真菌类群的物种多样性及其地理分布多样性,概括了它们在全球各大区域的分布特征。对近年来中国迅速发展的epichlo内生真菌的研究作了总结,最后展望了国际国内epichlo内生真菌资源探索的发展方向。特别指出:冷季型禾本科植物内生真菌在南美洲和亚洲,暖季型禾本科植物内生真菌在热带亚热带地区的研究还相对薄弱,值得今后继续加强探索和挖掘。     

Endophytic fungi in leaves of Lycopersicon esculentum Mill

Endophytic fungi were isolated from healthy tomato leaves from field-grown plants. Several surface-sterilization techniques were assayed for removing and killing epiphytes on tomato leaves. Surface-sterilization with an undiluted commercial solution of sodium hypochlorite was employed. To determine the spectrum of endophytes, samples were collected in February 1998 and 1999 from tomato plants (cultivar Tommy) cultivated in the experimental fields of Facultad de Ciencias Agrarias y Forestales, Universidad Nacional de La Plata, Buenos Aires, Argentina. In general, different spectra of species were isolated in 1998 and 1999.Alternaria alternata was the fungus most frequently isolated from tomato leaves in 1999, but it was the second most common species in 1998. In contrast, Colletotrichum gloeosporioides was the fungus most frequently isolated in 1998, but it was not found in 1999. Species of other genera, such as Cladosporium and Penicillium, were isolated in both years.     

Gliadin polymorphism in wild and cultivated einkorn wheats

To study the relationships between different species of the Einkorn group, 408 accessions of Triticum monococcum, T. boeoticum, T. boeoticum ssp. thauodar and T. urartu were analyzed electrophoretically for their protein composition at the Gli-1 and Gli-2 loci. In all the species the range of allelic variation at the loci examined is remarkable. The gliadin patterns of T. monococcum and T. boeoticum were very similar to one another but differed substantially from those of T. urartu. Several accessions of T. boeoticum and T. monococcum were shown to share the same alleles at the Gli-1 and Gli-2 loci, confirming the recent nomenclature that considers these wheats as different subspecies of the same species, T. monococcum. The gliadin composition of T. urartu resembled that of the A genome of polyploid wheats more than did T. boeoticum or T. monococcum, supporting the hypothesis that T. urartu, rather than T. boeoticum, is the donor of the A genome in cultivated wheats. Because of their high degree of polymorphism the gliadin markers may help in selecting breeding parents from diploid wheat germ plasm collections and can be used both to search for valuable genes linked to the gliadin-coding loci and to monitor the transfer of alien genes into cultivated polyploid wheats. Received: 8 July 1996 / Accepted: 12 July 1996     

Spontaneous chromosomal rearrangements in cultivated and wild barleys

Summary Four of 1,240 cultivated barley lines collected from different regions of the world and 3 of 120 lines of wild barley, Hordeum spontaneum C. Koch, carry spontaneous reciprocal translocations. Break-point positions and rearrangements in the interchanged chromosomes have been examined by both test crosses and Giemsa banding techniques. The four translocation lines in cultivated barley were all of Ethiopian origin and have the same translocation involving chromosomes 2 and 4. The breakpoints are at the centromeres of both chromosomes, resulting in interchanged chromosomes 2S+4S and 2L+4L (S=short arm, L=long arm). A wild barley line, Spont.II, also has translocated chromosomes 2 and 4 which are broken at the centromeres. The resultant chromosomes are, however, 2S+4L and 2L+4S. Another wild barley line, Spont.S-4, has interchanged chromosomes with breakpoints in the short arm of chromosome 3 and the long arm of chromosome 7. In addition, this line has a paracentric inversion in the short arm of chromosome 7 that includes a part of nucleolar constriction, resulting in two tandemly arranged nucleolar constrictions. The third wild barley line, Spont.S-7, has interchanged chromosomes with breakpoints in the long arms of both chromosomes 3 and 6. The translocated chromosome 3 is metacentric and the translocated chromosome 6 has a long arm similar in length to the long arm of chromosome 7.     

Furanocoumarins in seeds of wild and cultivated parsnip

The furanocoumarin content of ripe seeds of seven cultivars of Pastinaca sativa was compared to that of ripe seeds from a naturalized population in central Illinois. Five furanocoumarins were identified and quantified in the intact seeds. While seeds of wild and cultivated plants contain furanocoumarin components in identical proportions, seeds from wild plants contain almost three times the quantity of furanocoumarins on a dry weight basis as do seeds of cultivars.     

Glucosinolates of wild and cultivated Brassica species

Major differences were found in the occurrence of glucosinolates in the leaves of different wild species of the Brassica oleracea (2n = 18) group. The distribution of glucosinolates supports the present classification with the exception of the inclusion of both Tunisian and Sardinian populations within B. insuloris. The results also support the hypothesis of a multiphyletic origin of cultivated forms of B. oleracea from a number of wild species. In contrast, wild populations of B. rapa had very similar glucosinolate contents. Wild populations had a considerably higher total glucosinolate content than cultivars which may limit their usefulness in breeding programmes.