Uromycladium tepperianum, the gall rust fungus from Falcataria moluccana in Malaysia and Indonesia

Batai (Falcataria moluccana) is a valuable tree species for forest plantations in Malaysia and Indonesia. Since 1993, a gall rust disease has caused severe damage to all growth stages, from seedlings in the nursery to mature trees in the field. To identify the fungus causing gall rust disease on F. moluccana in Malaysia and Indonesia, study of the mode of infection and changes in the anatomy of infected cells were carried out in the anatomy laboratory. The disease in Malaysia and Indonesia is caused by Uromycladium tepperianum. The fungus produces three longitudinally ridged teliospores on each head, with spores measuring 13–20 μm wide and 17–28 μm long. The fungus is microcyclic, completing its entire life cycle on F. moluccana. This study confirmed that the teliospores themselves cannot infect the host. Under favorable conditions, about 10 h after inoculation, teliospores germinate to produce basidiospores that form penetration pegs about 6 h later, and it is this peg which penetrates the host cells directly through the epidermis. Pycnia, recognized as small brown pustules, break through the epidermis about 7 days after inoculation.     

乌拉甘草(豆科)的3个新异名

在考证了模式标本和查阅了大量腊叶标本的基础上,结合野外居群生物学调查工作,作者对分布于蒙古和我国境内的Glycyrrhiza alaschanicaGrankina、G.gobicaGrankina和G.soongoricaGrankina 3种甘草做了归并处理。认为它们属于乌拉甘草(G.uralensisFisch.ex DC.)的变异类型,均处理为乌拉甘草的异名。     

Ectomycorrhizal fungi are shared between seedlings and adults in a monodominant Gilbertiodendron dewevrei rain forest in Cameroon

Ectomycorrhizal networks may facilitate the establishment and survival of seedlings regenerating under the canopies of tropical forests and are often invoked as a potential contributor to monodominance. We identified ectomycorrhizal fungi in a monodominant Gilbertiodendron dewevrei (Fabaceae) rain forest in Cameroon, using sporocarps and ectomycorrhizae of three age categories (seedlings, intermediate trees, and large trees) and tentatively revealed nutrient transfer through ectomycorrhizal networks by measuring spontaneous isotopic (¹³C and ¹⁵N) abundances in seedlings. Sporocarp surveys revealed fewer ectomycorrhizal fungal taxa (59 species from 1030 sporocarps) than molecular barcoding of ectomycorrhizal roots (75 operational taxonomic units from 828 ectomycorrhizae). Our observations suggest that ectomycorrhizal fungal diversity is similar to that in other mixed tropical forests and provide the first report of the Tuber‐Helvella lineage in a tropical forest. Despite some differences, all age categories of G. dewevrei had overlapping ectomycorrhizal fungal communities, with families belonging to Thelephoraceae, Russulaceae, Sebacinaceae, Boletaceae, and Clavulinaceae. Of the 49 operational taxonomic units shared by the three age categories (65.3% of the ectomycorrhizal fungal community), 19 were the most abundant on root tips of all categories (38.7% of the shared taxa), supporting the likelihood of ectomycorrhizal networks. However, we obtained no evidence for nutrient transfer from trees to seedlings. We discuss the composition of the ectomycorrhizal fungal community among the G. dewevrei age categories and the possible role of common ectomycorrhizal networks in this rain forest.     

Taxonomic notes on the genus Otoptera (Phaseoleae, Fabaceae) in southern Africa

A taxonomic study of the genus Otoptera (tribe Phaseoleae) is presented. This distinct genus consists of two species, O. burchellii in southern Africa (Namibia, Botswana, South Africa and Zimbabwe) and O. madagascariensis endemic to Madagascar. The two species differ in the shape and size of leaflets, size and orientation of the spur located at the base of the wing petal, and also by size of the pod. A key to the two species is provided. This study focuses mainly on the southern African O. burchellii DC., which is described and illustrated. The species name is lectotypified and the known geographical distribution is recorded for the first time.     

Humidity-regulated dormancy onset in the Fabaceae: a conceptual model and its ecological implications for the Australian wattle Acacia saligna

Background and aims

Seed dormancy enhances fitness by preventing seeds from germinating when the probability of seedling survival and recruitment is low. The onset of physical dormancy is sensitive to humidity during ripening; however, the implications of this mechanism for seed bank dynamics have not been quantified. This study proposes a model that describes how humidity-regulated dormancy onset may control the accumulation of a dormant seed bank, and seed experiments are conducted to calibrate the model for an Australian Fabaceae, Acacia saligna. The model is used to investigate the impact of climate on seed dormancy and to forecast the ecological implications of human-induced climate change.

Methods

The relationship between relative humidity and dormancy onset was quantified under laboratory conditions by exposing freshly matured non-dormant seeds to constant humidity levels for fixed durations. The model was field-calibrated by measuring the response of seeds exposed to naturally fluctuating humidity. The model was applied to 3-hourly records of humidity spanning the period 1972–2007 in order to estimate both temporal variability in dormancy and spatial variability attributable to climatic differences among populations. Climate change models were used to project future changes in dormancy onset.

Key Results

A sigmoidal relationship exists between dormancy and humidity under both laboratory and field conditions. Seeds ripened under field conditions became dormant following very short exposure to low humidity (<20 %). Prolonged exposure at higher humidity did not increase dormancy significantly. It is predicted that populations growing in a temperate climate produce 33–55 % fewer dormant seeds than those in a Mediterranean climate; however, dormancy in temperate populations is predicted to increase as a result of climate change.

Conclusions

Humidity-regulated dormancy onset may explain observed variation in physical dormancy. The model offers a systematic approach to modelling this variation in population studies. Forecast changes in climate have the potential to alter the seed bank dynamics of species with physical dormancy regulated by this mechanism, with implications for their capacity to delay germination and exploit windows for recruitment.     

Lathyrus diversity: available resources with relevance to crop improvement – L. sativus and L. cicera as case studies

Background

The Lathyrus genus includes 160 species, some of which have economic importance as food, fodder and ornamental crops (mainly L. sativus, L. cicera and L. odoratus, respectively) and are cultivated in >1·5 Mha worldwide. However, in spite of their well-recognized robustness and potential as a source of calories and protein for populations in drought-prone and marginal areas, cultivation is in decline and there is a high risk of genetic erosion.

Scope

In this review, current and past taxonomic treatments of the Lathyrus genus are assessed and its current status is examined together with future prospects for germplasm conservation, characterization and utilization. A particular emphasis is placed on the importance of diversity analysis for breeding of L. sativus and L. cicera.

Conclusions

Efforts for improvement of L. sativus and L. cicera should concentrate on the development of publicly available joint core collections, and on high-resolution genotyping. This will be critical for permitting decentralized phenotyping. Such a co-ordinated international effort should result in more efficient and faster breeding approaches, which are particularly needed for these neglected, underutilized Lathyrus species.     

Flavanoids from Dalea elegans: Chemical reassignment and determination of kinetics parameters related to their anti-tyrosinase activity

In the first chemical investigation developed on the species Dalea elegans twenty years ago, the occurrence of two prenylated derivatives of pinocembrin was reported: 2′,4′-dihydroxy-5′-(1‴,1‴-dimethylallyl)-6-prenylpinocembrin (6PP) given as a new structure in this family of compounds, and another derivative of already known structure, 6-prenylpinocembrin (6P). In the present paper, their structures were again analyzed by using spectroscopic techniques, especially 2D NMR. Based on the evidence obtained it is proposed the reassignment of both flavanones as: 2′,4′-dihydroxy-5′-(1‴,1‴-dimethylallyl)-8-prenylpinocembrin (8PP) for the first and 8-prenylpinocembrin (8P) for the last. Additionally, triangularin, demethoxymatteucinol, comptonin and 7-hydroxy-5-methoxy-6,8-dimethylflavanone were isolated from aerial parts of D. elegans and informed by the first time for this species. All of these compounds were evaluated in vitro in relation to the antityrosinase effect by using a spectrophotometric method. Compound 8PP (IC₅₀ 2.32 ± 0.01 μM) exhibited the most potency and was two times more active than Kojic acid (IC₅₀ 4.93 ± 0.01 μM) used as a positive control. Triangularin also has shown an important inhibitory activity. Kinetic studies were performed for both compounds. Hence, new tyrosinase inhibitors with potential applications in pharmacy and cosmetic industry are presented.     

An experimentally induced host shift in a seed beetle

Many insects use a fairly well-defined set of host plants, but are occasionally observed on an atypical host. The seed beetle Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae: Bruchinae) has rarely been reported to attack lentil, which is distantly related to its usual legume hosts. An initial assay of an Asian beetle population revealed that none of the 100 larvae entering lentil seeds survived to adult emergence. Nevertheless, three attempts at mass selection, in which more than 2 000 adults were added to lentil seeds, eventually yielded self-sustaining populations. In each case, a severe bottleneck was followed by a rapid increase in survival, which exceeded 65% after only five generations and surpassed 85% in <20 generations. Subsequent large-scale experiments indicated that survival in lentil is initially <2% and that most larvae die before they have completely entered a seed. The only potential trade-off associated with rapid adaptation to lentil was a modest increase in the time required to develop in the ancestral host, mung bean. Reciprocal crosses between a lentil-adapted line (F10) and a mung-bean line produced offspring with intermediate survival, very long development times, and small size. Although the Asian population has been kept under uniform laboratory conditions for more than 200 generations, it appears to maintain rare alleles that permit the colonization of an extremely poor host. Such standing genetic variation can account for the sporadic appearance of unusual 'biotypes' among herbivorous insects.