Loquat as a crop model for successful deficit irrigation

During three consecutive seasons, two different deficit irrigation strategies were compared with control fully irrigated trees regarding their capacity to induce early bloom and harvest in “Algerie” loquat. The first strategy, a continuous deficit irrigation strategy, consisted in a uniform reduction of 20% water needs through the entire season; the second strategy, a regulated deficit irrigation approach, while accounting for the same global reduction of 20% loquat water needs, concentrated water shortages after harvest from mid-May through the end of August. Regulated deficit irrigation resulted more successful. Postharvest regulated deficit irrigation advanced full bloom 10–20 days depending on the season. Such enhancement led to more precocious and valuable yield, with an average increase of fruit value of 0.21 € kg⁻¹. The effects of continuous deficit irrigation were less noticeable and average fruit value was increased 0.08 € kg⁻¹. Yield and fruit quality were not affected for the different deficit irrigation strategies. Water savings established around 1450 m³ ha⁻¹ year⁻¹. Deficit irrigation rose water use efficiency up to more than a 40%.     

Competitive and allelopathic interference between soybean crop and annual wormwood (Artemisia annua L.) under field conditions

Annual wormwood interference on soybean crop growth and yield may result from competition and allelopathy, which are modulated by crop management. Allelochemicals released by annual wormwood (e.g. artemisinin) may affect the crop directly or indirectly through the effect on the nitrogen fixing symbiont, Bradyrhizobium japonicum. The objectives were (i) to quantify the crop response (i.e. biomass production, nodulation and yield) to weed interference and (ii) to determinate the relative change of competition and allelopathy interferences, when a sublethal dose of herbicide is applied. Two split plot field experiments with three replications were used. The experiment involved a factorial combination of five weed–crop density (soybean/annual wormwood, plants m^?2) levels: D1, pure soybean, 40/0 plants m^?2; D2, 40/2 plants m^?2; D3, 40/4 plants m^?2 and D4, 40/8 plants m^?2, and D5, pure annual wormwood, 0/8 plants m^?2, two activated carbon (allelopathy) levels: C?, with activated carbon (reduced allelopathy) and C+, non activated carbon applied (with allelopathy) and two herbicide levels: H?, untreated and H+, treated with a sub-lethal dose of glyphosate. Activated carbon to adsorb allelochemicals (with and without activated carbon) and glyphosate application (with and no herbicide) were assigned to sub-plots. Increasing weed density did not affect crop biomass at flowering, but changed nodule number and soybean yield with a different pattern depending on carbon and herbicide treatment. Relative crop yield decreased with increasing relative weed biomass. This decrease was particularly drastic when allelopathy was reduced by activated carbon and without herbicide application. The maximum yield losses of 33% in 2006 and 17% in 2007 were observed with the highest weed density (8 plants m^?2). In contrast, without carbon (high allelopathy level), soybean yield remained stable within the explored range of annual wormwood biomass, despite the fact that weed biomass at high densities (D4) was high enough to generate competition. The lack of response to increasing weed density could be related to the indirect effect of allelochemicals interacting with soil microorganisms (i.e. B. japonicum) that positively affected the nodulation (e.g. larger nodules in 2006 and increased nodules biomass due to higher number of roots in 2007 at high densities). With herbicide application, soybean yield of both carbon treatments remained stable when biomass of annual wormwood increased. This research provided strong evidence in support of the existence of positive effect of allelopathic and competitive interactions between annual wormwood and soybean crop under field conditions that may be overridden under herbicide application.     

Morphological characterization of the IVIA persimmon (Diospyros kaki Thunb.) germplasm collection by multivariate analysis

Diospyros kaki Thunb. originated in Eastern Asia, as evidenced of its culture in China as early as several centuries B.C. In the seventh century, persimmon was introduced to Japan and later, in the fourteenth century to Korea. There is no information about persimmon culture in Europe until the seventeenth century, with the spread over the world occurring in the eighteenth century. The genus Diospyros contains more than 400 species, with levels of ploidy ranging from diploid (2n = 2x = 30) up to nonaploid (2n = 9x = 135). The primary economic crop species is Diospyros kaki Thunb., which is mainly hexaploid (2n = 6x = 90) and includes hundreds of cultivars. Although a relatively recent introduction in Europe, the species has adapted well, and the genetic diversity have been expanded with culture and selection for the past 200 years in the Mediterranean basin. These locally adapted cultivars were evaluated with cultivars from Asian origin in a germplasm collection established at IVIA in Valencia, Spain. In this paper 27 cultivars from the IVIA collection were studied by multivariate analysis, and 37 variables were analyzed using a Principal Components Analysis and cluster analysis following the method UPGMA. Studies on correlations and significance among variables identified the most relevant ones, and thus provided information for a future core collection.     

Application to soil of disinfectants through irrigation reduces Verticillium dahliae in the soil and verticillium wilt of olive

The application of disinfectants through drip irrigation could be a feasible practice against verticillium wilt (Verticillium dahliae) of olive. OX-VIRIN (activated peroxide) and OX-AGUA AL25 (quaternary ammonium compounds) are two disinfectants that have shown efficacy against V. dahliae in irrigation water and potential for reducing the disease in young olive plants. In this work, various post-planting application strategies incorporating OX-VIRIN (once a month, or twice a month on alternate or successive weeks) or OX-AGUA AL25 (once a month, or twice a month on alternate weeks) were assessed for their effect on V. dahliae in soil, disease in olive trees, and olive yield, in a 2-year pot-experiment under natural environmental conditions. The disinfectants were injected via metering pumps into a drip irrigation system that irrigated olive trees planted in V. dahliae-inoculated soil. All the application strategies significantly reduced the total inoculum density in soil compared to controls with no disinfectants and noninoculated soil. The microsclerotia density was also significantly reduced in disinfested soils by 73.6–86.8%, depending on the strategy. The symptoms and infection incidence were always lower in treatments subjected to disinfestation. The treatment with OX-AGUA AL25 applied twice a month on alternate weeks most reduced the symptoms (by 53.0%) and colonization index (by 70.8%) with respect to untreated water control. This soil disinfestation also significantly strengthened the symptom remission. Tree growth and production were negatively affected by soil inoculation (reduced by 45.6% and 88.7%, respectively), but not so by disinfectants, which even relieved the reduction in inoculated soils, especially when OX-AGUA AL25 was applied.     

Carbon flux and growth in mature deciduous forest trees exposed to elevated CO2

Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees.     

Two Hungarian isolates of cucumber mosaic virus from sweet pepper (Capsicum annuum) and melon (Cucumis melo): Identification and antiserum preparation

Two Hungarian virus isolates from sweet pepper (K8) and melon (S4) were identified as cucumber mosaic virus (CMV) on the basis of host plant reactions and serology. The isolates were purified and antisera prepared. Homologous antiserum titers in double-diffusion tests were 256 (K8) and 512 (S4). They were serologically closely related to each other and to other CMV isolates. On the basis of symptoms they belong to different symptomatological groups of CMV; this was supported by serological properties. Sedimentation coefficients were c. 93 S, at 2 mg ml^–1. Purified preparations, stained with 2% uranyl acetate, showed spherical particles. In ELISA purified preparations reacted with each other's antisera.Samenvatting Twee hongaarse virusisolaten uit paprika (K8) en meloen (S4) werden geïdentificeerd als komkommermozaïekvirus (CMV) met behulp van toetsplanten en serologie. Beide isolaten werden gezuiverd en er werden antisera tegen bereid. De homologe titers van de antisera in de agar-geldiffusietoets bedroegen 256 (K8) en 512 (S4). K8 en S4 waren serologisch nauw verwant aan elkaar, evenals aan andere CMV-isolaten. Op grond van hun symptomen op toetsplanten behoren ze tot verschillende symptomatologische groepen van CMV. Dit laatste werd gesteund door de serologische eigenschappen. Beide isolaten hebben een sedimentatiecoëfficiënt van ca 93 S, bij een concentratie van 2 mg ml^–1. Gezuiverde preparaten, gekleurd met 2% uranylacetaat, bleken bolvormige deeltjes te bevatten. In ELISA reageerden gezuiverde preparaten van K8 en S4 met elkaars antisera.     

Contamination of soil with Toxocara eggs in urban (Prague) and rural areas in the Czech Republic

Contamination of soil with feline and canine ascarid eggs in public parks, backyards and sand pits in Prague, Czech Republic was investigated in this work. Soil samples from shelters and rural areas were also collected. The comparison of soil from different areas (urban, rural, backyards and shelters) exhibited significant difference (chi(2)=32.16, d.f.=3 and p<0.0001). The highest rate of contamination (45%) was found in backyards inhabited by feral cats. The eggs of Toxocara spp. were found in 20.4% of parks, 10% of shelters and 5% of rural samples. Mean egg density per sample from Prague parks was 6.2 eggs/100g of soil. In 126 composite samples from children's and pits, the prevalence of Toxocara eggs was 11.90%. The number of eggs in positive samples varied from 2 to 22 (per 100g). A high proportion (46.9%) of eggs was fully embryonated. There was no difference between the sand pits with or without formal exclusion of dogs (chi(2)=0.6, d.f.=1 and p<0.0001).     

Arbovirus isolations from mosquitoes in South Slovakia.

In the years 1973 and 1975 mosquitoes and some other Diptera (Tabanidae, Simuliidae, Hippoboscidae) were tested for virus. 13,924 mosquitoes, 75 horseflies and 60 blackflies were processed in 1973. Five strains of Tahyna virus were isolated from mosquito species Aedes vexans. 3,378 mosquitoes and 12 sheep keds were tested for virus in 1975. Twelve strains of Calovo virus were isolated from Anopheles maculipennis and one strain of Tahyna virus was obtained from Aedes vexans mosquitoes.