In vitro antifungal effect of phenylboronic and boric acid on Alternaria alternata

The ascomycete fungus Alternaria alternata causes early blight, one of economically the most important tomato diseases. Due to frequent use of fungicides, A. alternata has developed resistance with negative economic and environmental consequences. Research of new ways to control fungal pathogens has turned its eye to environmentally friendly chemicals with low toxicity such as boronic acids. The aim of our study was therefore to test the antifungal effects of phenylboronic and boric acid in vitro on A. alternata. We isolated the pathogen from a symptomatic tomato plant and determined the minimum inhibitory concentration of phenylboronic and boric acid on A. alternata mycelial growth using the poisoned food technique. The antifungal effect was tested on a wide range of phenylboronic and boric acid concentrations (from 0.04 % to 0.3 %) applied separately to agar with mycelial disc of the pathogen. After five days of incubation, phenylboronic acid at low concentration (0.05 %) completely inhibited mycelial growth. Boric acid, in turn, did not significantly slow down mycelial growth but did reduce sporulation and confirmed its fungistatic effect. Our findings point to the potential use of phenylboronic acid to control phytopathogenic fungi. This is, to our knowledge, the first report on its antifungal effect on an agriculturally important pathogen in vitro. Moreover, since A. alternata is also a human pathogen, these results may have clinical ramifications

Control of early blight fungus (Alternaria alternata) in tomato by boric and phenylboronic acid

Finding a suitable alternative to the small pool of existing antifungal agents is a vital task in contemporary agriculture. Therefore, intensive research has been conducted globally to uncover environmentally friendly and efficient agents that can suppress pathogens resistant to the currently used antimycotics. Here, we tested the activity of boric acid (BA) and its derivative phenylboronic acid (PBA) in controlling the early blight symptoms in tomato plants infected with pathogenic fungus Alternaria alternata. By following the appearance and intensity of the lesions on leaves of the tested plants, as well as by measuring four selected physiological factors that reflect plant health, we have shown that both BA and PBA act prophylactically on fungal infection. They did it by reducing the amount and severity of early blight symptoms, as well as by preventing deterioration of the physiological traits, occurring upon fungal inoculation. Phenylboronic acid was more efficient in suppressing the impact of A. alternata infection. Therefore, we conclude that BA, and even more so PBA, may be used as agents for controlling early blight on tomato plants, as they are both quite effective and environmentally friendly

3'-terminated Overhangs Regulate DNA Double-Strand Break Processing in Escherichia coli

Double-strand breaks (DSBs) are lethal DNA lesions, which are repaired by homologous recombination in Escherichia coli To study DSB processing in vivo, we induced DSBs into the E. coli chromosome by gamma irradiation and measured chromosomal degradation. We show that the DNA degradation is regulated by RecA protein concentration and its rate of association with ssDNA. RecA decreased DNA degradation in wild- type, recB and recD strains, indicating that it is a general phenomenon in E. coli On the other hand, DNA degradation was greatly reduced and unaffected by RecA in the recB1080 mutant (which produces long overhangs) and in a strain devoid of four exonucleases that degrade a 3' tail (ssExos). 3'-5' ssExos deficiency is epistatic to RecA deficiency concerning DNA degradation, suggesting that bound RecA is shielding 3' tail from degradation by 3'-5' ssExos. Since 3'-tail preservation is common to all these situations, we infer that RecA polymerization constitutes a subset of mechanisms for preserving the integrity of 3' tails emanating from DSBs, along with 3' tail's massive length, or prevention of their degradation by inactivation of 3'-5' ssExos. Thus, we conclude that 3' overhangs are crucial in controlling the extent of DSB processing in E. coli This study suggests a regulatory mechanism for DSB processing in E. coli, wherein 3' tails impose a negative feedback loop on DSB processing reactions, specifically on helicase reloading onto dsDNA ends

DIFFERENTIAL SUSCEPTIBILITY OF OLIVE VARIETIES TO OLIVE KNOT DISEASE IN ISTRIA

We performed a survey on susceptibility of two olive varieties ‘Leccino’ and ‘Picholine’ to olive knot disease in the area of Poreč in the years 2008 and 2009. The incidence of disease was determined by visual inspection of disease symptoms on olives according to recommendations of International Olive Council (IOC). The meteorological data were collected during 2007 and 2008. The damage caused by the disease was evaluated and the area where symptoms appeared was quantified. A rather high frequency of olive knot symptom was determined at all locations investigated. The new infection incidence was lower in 2009 for both varieties probably due to the winter copper treatment conducted. The variety ‘Picholine’ showed higher incidence of disease

Incidence and distribution of olive knot disease (Pseudomonas savastanoi pv. Savastanoi) on Istrian peninsula

Bakteriozni rak masline je bolest uzrokovana bakterijom Pseudomonas savastanoi pv. savastanoi (Pss). Pss je vrsta koja pripada kompleksu vrsta Pseudomonas syringae. Mehanizam zaraze s Pss uključuje sintezu dvaju hormona rasta – auksina i citokinina, koji uzrokuju pojavu hipertrofiranog tkiva, odnosno nekontrolirane i ubrzane diobe stanica na različitim biljnim organima masline (Olea europaea L.). Prisutnost bakterioznog raka masline zabilježena je u gotovo svim maslinarskim regijama u svijetu. Tijekom dvije godine (2021. i 2022.) obavljeno je terensko istraživanje i uzorkovanje zaraženog biljnog materijala kako bi se utvrdila prisutnost ovog patogena i na području hrvatskog dijela istarskog poluotoka. Ukupno 102 uzorka sakupljena su s 22 različite sorte u 45 maslinika. Prisutnost patogena određena je molekularnom metodom Real - time PCR u 32 (30 %) uzorka. Najveći udio pozitivnih uzoraka činile su sorte Leccino i Frantoio, koje su ujedno bile najzastupljenije sorte u istraživanim maslinicima. Veći tumori na simptomatičnim stablima masline utvrđeni su u sjevernim dijelovima Istre.Olive knot disease is caused by bacterium Pseudomonas savastanoi pv. savastanoi (Pss). The bacterium Pss belongs to the Pseudomonas syringae species complex. The mechanism of action used by Pss to establish an infection involves synthesis of two types of growth hormones - auxins and cytokinins. This mechanism leads to uncontrolled and accelerated cell division in different plant organs of olive tree (Olea europaea L.), which cause the appearance of hypertrophic tissue, known as knots. The presence of bacterial olive knot disease is recorded in almost all olive-growing regions in the world. In this research, a field survey and sampling of symtomatic plant material was carried out during 2021 and 2022 with aims to determine the distribution of olive knot disease in the Croatian part of the Istrian peninsula. Totally 102 samples were collected from 22 various olive varieties in 45 orchards. The bacterium Pss was identified using the Real-time PCR method in 32 (30%) of tested samples. The highest number of positive samples was recorded from susceptible Leccino and Frantoio varieties, which were the most widely grown varieties in sampled orchards in Istria. The formation of larger tumours on symptomatic olive trees was observed in olive orchards located in more northern regions of surveyed area

High quality and healthy seed guarantees high yield

Ulaskom Hrvatske u EU usljedile su velike promjene u zakonskoj regulativi proizvodnje, dorade i distribucije sjemena. Prije ulaska u EU na većini poljoprivrednih gospodarstava sijano je isključivo certificirano sjeme žitarica. Stupanjem na snagu Zakona o izmjenama i dopunama Zakona o zaštiti biljnih sorti u Republici Hrvatskoj (NN 124/11) koji je usklađen s propisima EU na gospodarstvu se smije sijati tzv. „farmerovo sjeme“. U nekim zemljama, članicama EU, takvo sjeme se sije isključivo po propisanim uvjetima. Kod nas ti uvjeti još nisu strogo propisani te se pojam "farmerovo" ili "farmersko sjeme" često među poljoprivrednim proizvođačima poistovjećuje s pojmom "tavanuša", čijom sjetvom se u tlo mogu unijeti uzročnici biljnih bolesti i korovi. Cilj provedenog istraživanja je odrediti kvalitetu certificiranog, farmerovog i farmerovog sjemena nepoznate sorte (tavanuša). Istraživanje je provedeno u ovlaštenom laboratoriju za kontrolu kvalitete poljoprivrednog sjemena Visokog gospodarskog učilišta u Križevcima na pet uzoraka certificiranog sjemena pšenice iz dvije ovlaštene dorade, pet uzoraka farmerovog sjemena i pet uzoraka farmerovog sjemena nepoznate sorte (tavanuša). Ispitivano je zdravstveno stanje sjemena, proveden je test ispiranja sjemena (kontrola na prisutnost hlamidospora uzročnika smrdljive snijeti Tilletia spp.), klijavost i čistoća sjemena. Rezultati istraživanja pokazuju da je sjetva certificiranog sjemena jedini siguran put do visokog i kvalitetnog prinosa. Certificirano i kvalitetno dorađeno sjeme ima veću energiju i klijavost, uzročnici bolesti imaju nižu pojavnost te nema sjemena korova.Croatian accession to the EU brought about big changes in the legislation of seed production, processing and distribution. Before joining the EU, only certified grain seed was planted on most farms. When the Act on Amendments to the Act on Protection of Plant Varieties in the Republic of Croatia (OG 124/11) that complied with the EU legislature came into force, farms were allowed to plant the so-called “farmer\u27s seed”. In some EU Member States farmer\u27s seed is planted only under prescribed conditions. Since those conditions are still not strictly regulated in Croatia, farmer\u27s seed is in Croatia often identified as a seed of unknown variety and origin, which can bring plant pathogens causing diseases and weeds into soil when planted. The purpose of this research was to determine the quality of certified seed, farmer\u27s seed, and farmer\u27s seed of unknown variety. The research was conducted in the Laboratory for Agricultural Seed Quality Testing at the College of Agriculture in Križevci. Five samples of certified wheat seed from two authorized seed producers, five farmer\u27s seed samples and five farmer\u27s seed samples of unknown variety were used. Health, germination and purity of all of seed samples were tested, and seed rinsing (testing for the presence of chlamydospores of fungus Tilletia spp.) was performed. The results of this research showed that certified seed planting is the only safe way to ensure both high quality and yield. Certified and well processed seed not only has higher energy and seed germination power, and lower incidence of plant pathogens, but it does not contain weed seeds

Regulation of ssb Gene Expression in Escherichia coli

: Bacterial SSB proteins, as well as their eukaryotic RPA analogues, are essential and ubiquitous. They avidly bind single-stranded DNA and regulate/coordinate its metabolism, hence enabling essential DNA processes such as replication, transcription, and repair. The prototypic Escherichia coli SSB protein is encoded by an ssb gene. Although the ssb gene promoters harbor an SOS box, multiple studies over several decades failed to elucidate whether ssb gene expression is inducible and SOS dependent. The SOS regulon is comprised of about 50 genes, whose transcription is coordinately induced under stress conditions. Using quantitative real-time PCR, we determined the ssb gene expression kinetics in UV- and γ-irradiated E. coli and revealed that ssb gene expression is elevated in irradiated cells in an SOS-dependent manner. Additionally, the expression of the sulA gene was determined to indicate the extent of SOS induction. In a mutant with a constitutively induced SOS regulon, the ssb gene was overexpressed in the absence of DNA damage. Furthermore, we measured ssb gene expression by droplet digital PCR during unaffected bacterial growth and revealed that ssb gene expression was equal in wild-type and SOS− bacteria, whereas sulA expression was higher in the former. This study thus reveals a complex pattern of ssb gene expression, which under stress conditions depends on the SOS regulon, whereas during normal bacterial growth it is unlinked to SOS induction. The E. coli ssb gene is SOS regulated in such a way that its basal expression is relatively high and can be increased only through stronger SOS induction. The remarkable SOS induction observed in undisturbed wild-type cells may challenge our notion of the physiological role of the SOS response in bacteria

Release of Trichoderma viride Spores from Microcapsules Simultaneously Loaded with Chemical and Biological Agents

Recent studies of bioactive agents, simultaneous encapsulation in chitosan/alginate microcapsules revealed that encapsulation in the same compartment does not inhibit activity either of Trichoderma viride spores nor copper cations. The objective of this work was to investigate the influence of formulation variables (concentration of copper cations, chitosan layer and microcapsule size) on T. viride spores release. Results showed that the increase in copper cation concentration promoted, but the increase in microcapsule size and presence of the chitosan layer on microcapsule surface reduced T. viride spores release. Fitting to simple Korsmeyer–Peppas empirical model elucidated the underlying mechanism of release. Fickian diffusion controlled release from microcapsules without chitosan layer and smaller microcapsules with chitosan layer, whereas anomalous diffusion mechanism (a combination of the diffusion and erosion mechanisms) was found to be the rate-controlling mechanism from larger microcapsules with chitosan layer. The investigation showed that proper selection of formulation variables helps in designing microcapsules with the desirable release of T. viride for plant protection and nutrition