Current research on phytopathogenic fungi: an overview

The majority of plant pathogens comprising about 60% of the total are belonging to a group of eukaryotic microorganisms, commonly known as FUNGI although this name obviously covers a number of organisms that are not fungi in a strict sense [1]. Yet, all these plant pathogens, having different systematic positions within the livings, are of significance as far as agricultural crop production is concerned.Mycologists in the past were primarily interested in identifying fungal diseases, describing the fungi, studying their life cycle in relation to environment and looking for effective control measures. A big step forward was when investigations expanded toward the physiology of plant diseases and disease resistance. Meanwhile fungal genetics has developed providing a better understanding of plant-fungus relations. Recently, with the introduction of molecular techniques, new approaches of research, such as molecular taxonomy and molecular genetics have been established and the molecular methods were applied in other related fields of studies.For the illustration of changes in research interest worldwide, the main research topics and all the contributions (poster presentations) accepted at and published by the 7th International Congress of Plant Pathology held in Edinburgh, Scotland between 9-16 August 1998 have been scanned. Based on these, some of the most promising research trends with a few examples will be accounted here and then a short overview of what has recently been done by Hungarian mycologists on the subject will be given

Induction of Resistance with Benzothiadiazole in Sunflower: a Comparison of Biotrophic vs. Necrotrophic Pathosystems

In the present work we aimed at comparing the effect of benzothiadiazole (BTH) treatment on defence reactions of sunflower plants to downy mildew and white rot diseases. BTH treatment resulted in reduced disease symptoms in biotrophic and in the early stage of the necrotrophic interactions. To get a better insight into the effect of BTH, changes in the activities of polyphenol oxidase and peroxidase enzymes, as well as the expression of the host response-associated sunflower genes were examined in the plants. Inoculation with Plasmopara halstedii enhanced the polyphenol oxidase and peroxidase enzyme activities, while inoculation with Sclerotinia sclerotiorum did it only at 4 dpi. However, most importantly, in each case extracts from BTH pretreated and inoculated plants showed the highest polyphenol oxidase and peroxidase enzyme activities. Similarly, the accumulation of GST and PDF transcripts was detected following inoculations with both biotrophic and necrotrophic pathogens, and again, BTH pre-treatment enhanced GST and defensine gene activities in the inoculated plants. We suggest that induction of enzyme activities, as well as of the elevated expression of GST, PDF and PR5 genes by BTH pre-treatment may be a significant part of the induced resistance of sunflower to downy mildew and white rot (white mold)

Dogs’ expectation about the signalers’ body size by virtue of their growls

Several studies suggest that dogs, as well as primates, utilize a mental representation of the signaler after hearing its vocalization and can match this representation with other features provided by the visual modality. Recently it was found that a dogs' growl is context specific and contains information about the caller's body size. Whether dogs can use the encoded information is as yet unclear. In this experiment, we tested whether dogs can assess the size of another dog if they hear an agonistic growl paired with simultaneous video projection of two dog pictures. One of them matched the size of the growling dog, while the other one was either 30% larger or smaller. In control groups, noise, cat pictures or projections of geometric shapes (triangles) were used. The results showed that dogs look sooner and longer at the dog picture matching the size of the caller. No such preference was found with any of the control stimuli, suggesting that dogs have a mental representation of the caller when hearing its vocalization

Why do dogs (Canis familiaris) select the empty container in an observational learning task?

Many argue that dogs show unique susceptibility to human communicative signals that make them suitable for being engaged in complex co-operation with humans. It has also been revealed that socially provided information is particularly effective in influencing the behaviour of dogs even when the human’s action demonstration conveys inefficient or mistaken solution of task. It is unclear, however, how the communicative nature of the demonstration context and the presence of the human demonstrator affect the dogs’ object-choice behaviour in observational learning situations. In order to unfold the effects of these factors, 76 adult pet dogs could observe a communicative or a non-communicative demonstration in which the human retrieved a tennis ball from under an opaque container while manipulating another distant and obviously empty (transparent) one. Subjects were then allowed to choose either in the presence of the demonstrator or after she left the room. Results showed a significant main effect of the demonstration context (presence or absence of the human’s communicative signals), and we also found some evidence for the response-modifying effect of the presence of the human demonstrator during the dogs’ choice. That is, dogs predominantly chose the baited container, but if the demonstration context was communicative and the human was present during the dogs’ choice, subjects’ tendency to select the baited container has been reduced. In agreement with the studies showing sensitivity to human’s communicative signals in dogs, these findings point to a special form of social influence in observational learning situations when it comes to learning about causally opaque and less efficient (compared to what comes natural to the dog) action demonstrations

Left gaze bias in humans, rhesus monkeys and domestic dogs

While viewing faces, human adults often demonstrate a natural gaze bias towards the left visual field, that is, the right side of the viewee’s face is often inspected first and for longer periods. Using a preferential looking paradigm, we demonstrate that this bias is neither uniquely human nor limited to primates, and provide evidence to help elucidate its biological function within a broader social cognitive framework. We observed that 6-month-old infants showed a wider tendency for left gaze preference towards objects and faces of different species and orientation, while in adults the bias appears only towards upright human faces. Rhesus monkeys showed a left gaze bias towards upright human and monkey faces, but not towards inverted faces. Domestic dogs, however, only demonstrated a left gaze bias towards human faces, but not towards monkey or dog faces, nor to inanimate object images. Our findings suggest that face- and species-sensitive gaze asymmetry is more widespread in the animal kingdom than previously recognised, is not constrained by attentional or scanning bias, and could be shaped by experience to develop adaptive behavioural significance

Development of Gaze Following Abilities in Wolves (Canis Lupus)

The ability to coordinate with others' head and eye orientation to look in the same direction is considered a key step towards an understanding of others mental states like attention and intention. Here, we investigated the ontogeny and habituation patterns of gaze following into distant space and behind barriers in nine hand-raised wolves. We found that these wolves could use conspecific as well as human gaze cues even in the barrier task, which is thought to be more cognitively advanced than gazing into distant space. Moreover, while gaze following into distant space was already present at the age of 14 weeks and subjects did not habituate to repeated cues, gazing around a barrier developed considerably later and animals quickly habituated, supporting the hypothesis that different cognitive mechanisms may underlie the two gaze following modalities. More importantly, this study demonstrated that following another individuals' gaze around a barrier is not restricted to primates and corvids but is also present in canines, with remarkable between-group similarities in the ontogeny of this behaviour. This sheds new light on the evolutionary origins of and selective pressures on gaze following abilities as well as on the sensitivity of domestic dogs towards human communicative cues

Inhibitory control, but not prolonged object-related experience appears to affect physical problem-solving performance of pet dogs

Human infants develop an understanding of their physical environment through playful interactions with objects. Similar processes may influence also the performance of non-human animals in physical problem-solving tasks, but to date there is little empirical data to evaluate this hypothesis. In addition or alternatively to prior experiences, inhibitory control has been suggested as a factor underlying the considerable individual differences in performance reported for many species. Here we report a study in which we manipulated the extent of object-related experience for a cohort of dogs (Canis familiaris) of the breed Border Collie over a period of 18 months, and assessed their level of inhibitory control, prior to testing them in a series of four physical problem-solving tasks. We found no evidence that differences in object-related experience explain variability in performance in these tasks. It thus appears that dogs do not transfer knowledge about physical rules from one physical problem-solving task to another, but rather approach each task as a novel problem. Our results, however, suggest that individual performance in these tasks is influenced in a complex way by the subject’s level of inhibitory control. Depending on the task, inhibitory control had a positive or a negative effect on performance and different aspects of inhibitory control turned out to be the best predictors of individual performance in the different tasks. Therefore, studying the interplay between inhibitory control and problem-solving performance will make an important contribution to our understanding of individual and species differences in physical problem-solving performance