Solanum tuberosum cultivars, Solanum tuberosum × Solanum tuberosum subsp. andigena hybrids and breeding clones with different time to maturity were screened for drought tolerance in field plots located in the coastal desert of Peru. Variation for drought tolerance was illustrated by clone-dependent differences in tuber yield and yield loss under drought conditions. Neither changes in stomatal conductance nor maximum quantum yield of chlorophyll fluorescence were quantitatively associated with yield or yield loss under drought. In contrast, relative vegetation index (reflectance at 800 nm / reflectance at 650 nm) and normalized difference vegetation index [(reflectance at 800 nm -reflectance at 650 nm) / (reflectance at 800 nm + reflectance at 650 nm)] on day 25 and day 40 after drought were correlated with yield. The vegetation indices are related to leaf area index and above ground biomass, which appeared to be major determinants for yield in the tested cultivars under drought. Nitrate reductase activity was significantly decreased in drought-exposed plants, but activity depletion was independent of yield or yield maintenance. Putative drought tolerance genes were differentially expressed in leaves of water stressed genotypes. Induction of the protein phosphatase 2C gene was positively associated with yield maintenance under drought. Furthermore, Potato Research (2007) 50:71-85

Responses to prolonged drought and recovery from drought of two South American potato (Solanum tuberosum L. ssp. andigena (Juz & Buk) Hawkes) landraces, Sullu and Ccompis were compared under field conditions. Physiological and biomass measurements, yield analysis, the results of hybridisation to a potato microarray platform (44 000 probes) and metabolite profiling were used to characterise responses to water deficit. Drought affected shoot and root biomass negatively in Ccompis but not in Sullu, whereas both genotypes maintained tuber yield under water stress. Ccompis showed stronger reduction in maximum quantum yield under stress than Sullu, and less decrease in stomatal resistance. Genes associated with PSII functions were activated during recovery in Sullu only. Evidence for sucrose accumulation in Sullu only during maximum stress and recovery was observed, in addition to increases in cell wall biosynthesis. A depression in the abundance of plastid superoxide dismutase transcripts was observed under maximum stress in Ccompis. Both sucrose and the regulatory molecule trehalose accumulated in the leaves of Sullu only. In contrast, in Ccompis, the raffinose oligosaccharide family pathway was activated, whereas low levels of sucrose and minor stress-mediated changes in trehalose were observed. Proline, and expression of the associated genes, rose in both genotypes under drought, with a 3-fold higher increase in Sullu than in Ccompis. The results demonstrate the presence of distinct molecular and biochemical drought responses in the two potato landraces leading to yield maintenance but differential biomass accumulation in vegetative tissues.

The effect of habitat loss on the dynamics of myxomycete assemblages has been poorly studied thus far. For this reason, a premontane moist forest surrounded by human-created pastures on the Caribbean slope of Costa Rica was selected to carry out a pilot ecological evaluation using a systematic approach. In the area of study, a series of forest zones representing a gradual continuum of habitat variation was selected and characterized using structural forest parameters. Fruiting bodies of myxomycetes were surveyed across these zones and microhabitat variables were measured when fruiting bodies were found. Results indicated that species richness, species diversity and the number of unique species recorded as fruiting bodies increased linearly from areas without suitable habitat to areas with complete suitable habitats and such pattern was shown to be correlated with canopy openness. Since the latter factor is clearly dissimilar across areas with structural differences in the forest being studied, the results presented herein suggest that myxomycetes are affected by the modification and loss of suitable habitats.

No abstract

During field surveys of myxomycetes in Central America, 2 previously unrecorded genera and 4 species, viz. Craterium muscorum Ing, Dictydiaethalium dictyosporum Nann.-Bremek., Physarina echinocephala Höhn, and Stemonaria rufipes, were identified. Some of these are new for the Neotropics. These noteworthy range extensions of these species to the Mesoamerican biodiversity hotspot adds to our knowledge of rarely recorded myxomycetes worldwide. Images of the more relevant taxonomic characters are provided, and for some species, this is the first illustrations with macro and microphotographs and scanning electron microscopy images.

. 2011 -Physarella oblongacentered bioassays for testing the biological activity of myxomycetes. Mycosphere 2 (6), 637-644, Doi 10.5943/mycosphere/2/6/4To study the trypanocidal, antibacterial, antifungal activity and cytotoxicity of myxomycetes, a rapid assessment focused on the species Physarella oblonga was carried out. Optimum conditions for culturing were utilized to develop a protocol that was adequate for bioanalysis of chemical compounds. Nuclear magnetic resonance (NMR) and mass spectroscopy (MS) detected the presence of stigmasterol and fatty acids in plasmodial extracts of Ph. oblonga through H1 analysis. These plasmodial extracts showed low toxicity and positive activity against epymastigote forms of Trypanosoma cruzi. This activity was significantly higher than the activity shown by one of the controls used. Similarly, the extracts from an unidentified species of myxomycete showed strong antimicrobial and antifungal activities against isolated strains of Bacillus cereus, Fusarium oxysporum and Rhizoctonia solani, whereas the myxomycete Physarum melleum displayed growth inhibition of the phytopathogen F. oxysporum. These results showed that with the use of an appropriate methodology, bioprospective analysis can be carried out on myxomycetes. In addition, this is apparently the first report on the antifungal and antiparasitic potential of myxomycetes.

There are few published studies providing information about macrofungal biology in a context of forest dynamics in tropical areas. For this study, a characterization of above-ground standing tree biomass and carbon stocks was performed for four different forest subtypes within two life zones in Costa Rica. Fungal productivity and reproductive success were estimated and analyzed in the context of the forest systems studied and results showed fungal dynamics to be a complex and challenging topic. In the present study, fungal productivity was higher in forest patches with more tree density but independent from life zones, whereas fungal biomass was higher in premontane areas with ectomycorrhizal dominant trees. Even though some observed patterns could be explained in terms of climatic differences and biotic relationships, the high fungal productivity observed in dry forests was an interesting finding and represents a topic for further studies.

Los artículos publicados se distribuye bajo una Licencia Creative Commons Atribución 4.0 Internacional (CC BY 4.0) basada en una obra en http://www. revistas.una.ac.cr/ambientales., lo que implica la posibilidad de que los lectores puedan de forma gratuita descargar, almacenar, copiar y distribuir la versión final aprobada y publicada del artículo, siempre y cuando se mencione la fuente y autoría de la obra.