Argentinian potato leafroll virus P0 protein: Novel activities for a previously known suppressor

The potato leafroll virus (PLRV) P0 protein (P0^PL) is a suppressor of RNA silencing. In this study, we showed that P0 protein from an Argentinian isolate of PLRV (P0^PL-Ar) has an additional activity not described for other PLRV or P0 proteins from poleroviruses. Besides reporting that P0^PL-Ar displays both local and systemic silencing suppressor activity, we demonstrated, for the first time, that P0^PL-Ar impedes accumulation of dsRNA-derived siRNAs. We also showed that P0^PL-Ar interacts with Solanum tuberosum SKP1 orthologue (StSKP1) and triggers destabilization of ARGONAUTE 1 (AGO1) and that these actions are mediated by the F-box-like domain. A mutant in the GW/WG motif within the P0^PL-Ar F-box-like motif lost the suppression activity, the interaction with StSKP1 and abolished AGO1 decay. Interestingly, a mutant in the L76/P77 residues within the P0^PL-Ar F-box-like motif, which lost the suppression activity and the interaction with StSKP1, retained the capacity to enable AGO1 decay. Thus, unlike other P0 proteins of previously characterized poleroviruses, P0^PL-Ar seems to have a dual activity, according to the findings of this study. This protein would act at both an upstream and a downstream step of the RNA silencing pathway: upstream of Dicer-like enzyme (DCL)-mediated primary siRNA production and downstream at the RNA-induced silencing complex (RISC) complex level. Our results contribute to the understanding of the different ways PLRV P0 proteins function as silencing suppressors.     

Wildlife translocation: the conservation implications of pathogen exposure and genetic heterozygosity

Background

Efficient division of reproductive labor is a crucial characteristic of social insects and underlies their ecological and evolutionary success. Despite of the harmonious appearance of insect societies, nestmates may have different interests concerning the partitioning of reproduction among group members. This may lead to conflict about reproductive rights. As yet, few studies have investigated the allocation of reproduction among queens in multi - queen societies ("reproductive skew"). In the ant Leptothorax acervorum, reproductive skew varies considerably among populations. While reproduction is quite equally shared among nestmate queens in most populations from boreal Eurasia (low skew), colonies from populations at the edge of the species' range are characterized by "functional monogyny," i.e., high skew. The proximate mechanisms underlying high skew, in particular how workers influence which queen lays eggs, are not well understood. We investigated the behavior of queens and workers in functionally monogynous colonies of L. acervorum from two mountain ranges in central Spain.

Results

We provide evidence for both queen and worker influence on the outcome of conflict over reproduction in colonies of L. acervorum from Spain. The patterns of queen - queen aggression and worker - queen grooming and feeding after hibernation allowed predicting, which queen later began to lay eggs. In contrast, worker aggression towards queens was not clearly associated with a queen's future reproductive success. Queen - queen and worker - queen aggression differed in quality: queens typically engaged in ritualized dominance behavior, such as antennal boxing, while workers also attacked queens by biting and prolonged pulling on their legs and antennae. In several cases, overt worker aggression led to the expulsion of queens from the nest or their death.

Conclusion

We conclude that queens of L. acervorum from Spain establish rank orders by ritualized dominance interactions, such as antennal boxing. Workers may reinforce these hierarchies by preferentially feeding and grooming high ranking queens and attacking lower ranking queens. Aggressive worker policing may thus stabilize functional monogyny. Optimal skew models predict that high skew in ants is associated with high dispersal costs. In central Spain, L. acervorum is restricted to small patches at higher elevations, which presumably makes dispersal and colony founding difficult. Because of the ecological requirements of L. acervorum and the predicted large impact of global change on central Spain, the functionally monogynous populations of this ant must be considered as threatened.     

Precision agriculture research in sub-Saharan Africa countries: a systematic map

Precision agriculture (PA) has a huge potential for growth in sub-Saharan Africa (SSA), but it faces a number of social-economic and technological challenges. This study sought to map existing PA research and application in SSA countries following the methodology for systematic mapping in environmental sciences. After screening for relevance, the initial about 7715 articles was reduced to 128. Results show that most of the studies were conducted in countries with socio-economic and technological advancement, mainly South Africa followed by Nigeria and Kenya. The studies were conducted at various scales ranging from field to country level with field scale studies being the most common. Most studies were conducted in relatively small farms typical of most farmlands in SSA. Studies done in relatively large farms are fewer, and such farms would likely belong to a few organisations and individuals with high economic capacity. Many of these studies have been conducted by researchers from outside SSA and a combination of researchers from within and outside SSA. However, based on authorship of the articles, it appears that most of the studies conducted in SSA on precision agriculture have either involved or depended on non-African researchers. It is concluded that there have been significant strides towards use of precision agriculture in SSA. However, with about 21 countries having no research done, there exists greater potential for precision agriculture in the region. Besides, there is need for more research to investigate the low usage of precision agriculture for livestock management.

     

Distribution of Vegetatively Compatible Populations of Rhizoctonia solani AG1-IA in a Field Planted with Different Host Species

To understand the distribution pattern and divergence of Rhizoctonia solani in a field over a 4-year period, R. solani AG1-IA isolates were collected from diseased tissues of several crops. Pairing tests between isolates to detect hyphal anastomosis and vegetatively compatible population (VCP) groupings were done on 2% water agar and potato dextrose agar. A single VCP of R. solani AG1-IA dominated a large upland crop field at the Institute of Plant Breeding, University of the Philippines at Los Ba?os. The VCP changed more slowly and at a lower frequency as compared to other reports. Received 27 September 1999/ Accepted in revised form 3 February 2000     

Interaction between jasmonic and gibberellic acids on in vitro tuberization of potato plantlets

Summary A reverse of the delaying effect of gibberellic acid (GA₃) was observed in in vitro tuberization of potato plantlets when the medium contained 0.8×10⁻⁵ M jasmonic acid (JA). The promoting effect of JA seemed to be correlated with the initial absence of growing roots, probably through direct activity of JA in microtuber-producing buds in the stoloniferous shoots. This is based on the fact that JA did not inhibit root growth a posteriori. Endogenous gibberellins (GAs) synthesized by roots did not interfere with the previous activity of JA in tuberization. The absence of a JA promoting-effect on tuberization of previously-rooted plantlets could be related to the capacity of potato roots to synthesize endogenous GAs which might antagonize the JA effect on buds of stoloniferous shoots.     

Mit neuen Verfahren gegen Fruchtwickler in Kleingartenanlagen

The availability of pesticides in private gardens is limited by local law in the State of Baden-Württemberg in south-west Germany. Only 26 insecticides, fungicides and molluscicides are permitted. Hence, only pesticides such as Bacillus thuringiensis, Granulosis Virus, pyrethrum or the pheromone mating disruption method (PMDM) can be used for moth control in apple. The use of beneficials like Trichogramma sp. or Chrysoperla carnea is not limited. PMDM had not been previ-ously investigated in allotments until the experiments reported here were carried out in 1998 and 1999. In these experiments, PMDM was compared with the use of the egg parasites, Trichogramma dendrolimi and T. cacoeciae. The observations were done in 102 allotments, each of about 300 m². The gardeners are members of a special club for the allotments and they often organize the bulk acquisition of plants or fertilizers for the club. Sometimes the club obtains plant protection products when something has to be done in all allotments. The codling moth and the plum fruit moth are important pests in these allotments.In 1997, attacks of codling moth were generally low throughout the southern Germany. This was reflected in the allotments where there was less than one per cent fruit damage with PMDM or the egg parasites the following year. During 1999, the attacks were generally much higher resulting in a higher use of insecticides in commercial German orchards. In the allotments, about six to eight per cent of fruits were damaged by the codling moth in both experimental treatments.The results indicate that PMDM can be successful in allotments and is equally as effective as the use of egg-parasites. But further experiments are required.     

Die Einführung der Arsenverstäubung vom Flugzeug aus in die Praxis der Forstschädlingsbekämpfung

Ohne Zusammenfassung     

Soil organic carbon in cropping sequences with predominance of soya bean in the argentinean humid Pampas

Soya bean (Glycine max (L.) Merr.) monoculture can lead to a decrease in labile fractions of soil organic carbon (SOC). This study sought to evaluate the effects of cover crops (CC), application of fertilizer, and crop rotation on SOC, particulate organic carbon (POC), and soil carbon input in soya bean-based crop sequences under a no-till cropping system in the Argentinean Humid Pampas. Five crop sequences at two sites differing in initial SOC were evaluated: continuous soya bean (Sb), continuous soya bean fertilized with phosphorus (P) and sulphur (S) (Sbf), grass CC / PS-fertilized soya bean (CC/Sbf), nitrogen (N)-fertilized CC / PS-fertilized soya bean (CCf/Sbf) and NPS-fertilized crop rotation with high intensification sequence index (ISI) (Rot). At 0–5 cm, SOC and POC were higher (p < .05) in the sequences with higher residue-C supply (CC/Sbf; CCf/Sbf and Rot) at both sites. Changes in SOC at 0–20 cm simulated by AMG model closely tracked measured results at 0–20 cm. Findings from this study suggest that the inclusion of CC or crop rotation with high ISI improved C balance in soils under crop sequences with soya bean predominance.