A comprehensive investigation of the effect of thyme oil-loaded chitosan nanoparticles on aphid-mediated transmission of potato virus Y.

Potato virus Y (PVY) is a destructive and widespread virus in a number of important crops, including potato. Aphid vectors spread this viral infection between plants in a non-persistent manner, and the green peach aphid (Myzus persicae) is the most efficient known vector. In this research, we investigated five cuticle proteins (CuPs) which are expected to be involved in virus transmission at the stylet of aphids. In an RNA interference (RNAi) gene-silencing assay with the green peach aphids (M. persicae), we evaluated the impact of these CuPs on the transmission of PVY with potato and tobacco plants. Using an oral RNAi bioassay where the aphids pierce-suck in an artificial diet that was supplemented with gene-specific dsRNA, the expression of only two CuPs, mpcp2 (DQ108935) and mpcp1 (AF435075.1), could be decreased by 63 and 75%, respectively. Expression of the other three CuPs could not be affected. Subsequently, we investigated what the effect is of the RNAi-mediated gene silencing on the transmission of PVY from potato to tobacco plants. These results showed with a high certainty of 99.5%, for the first time in vivo, a significant involvement of MPCP2 with a reduction of 47% (compared to the dsGFP control) in the transmission of PVY. For MPCP1, the effect was smaller with a reduction of 19% and lower certainty of 86%.

Within plant distribution of Potato Virus Y in hairy nightshade ( Solanum sarrachoides): An inoculum source affecting PVY aphid transmission

Plant viruses give rise to potential loss to global crop production and have the potential to cause widespread damage. Potato virus Y (PVY) is a plant virus that belongs to the genus Potyvirus and the family Potyviridae and it is considered a major concern, particularly for solanaceous crops such as potatoes. PVY represents the largest cluster of plant viruses, encompassing over 111 recognized and 86 tentative species across 30 plant families. Its broad geographic distribution extends over the globe, with a notable prevalence in temperate and subtropical climates where potato cultivation is extensive. As a monopartite virus with a single strand of positive-sense RNA, PVY manifests diverse strains that induce varied symptoms in potato plants, presenting challenges in strain categorization. PVY transmission occurs through both vertical and horizontal pathways, with aphids being the most efficient vectors. Mechanical transmission and agricultural practices can also contribute to the spread of the virus, impacting the growth and physiological functions of plants. Climate factors are very important in shaping the dynamics of plant viral diseases in plants, with varied climatic conditions fostering the emergence of more virulent virus strains. Temperature, humidity and precipitation, directly and indirectly, influence vector abundance, virus replication and host susceptibility, thereby modulating PVY transmission dynamics. Managing PVY in potato crops requires a multifaceted approach due to its significant economic impact and complex transmission dynamics. Strategies include cultural methods, host-plant resistance, chemical interventions, vector control and emerging techniques like cryotherapy and nanomaterial applications. Understanding the profound impact of climate variables on the epidemiology and management of PVY underscores the urgent need for proactive measures. This study offers a comprehensive review of recent findings regarding the intricate relationship between climate variables such as temperature, CO2 levels, light intensity, relative humidity, rainfall and wind velocity-and their significant influence on PVY infection severity and aphid vector population dynamics. Insights gleaned from this review will aid in formulating enhanced management strategies to combat the spread of this significant viral pathogen.

Natural Preservation Strategy for Green Olives: Effects of Thyme Oil-Enriched Chitosan Edible Films on Physicochemical, Microbiological, and Sensory Attributes.

Every year potato growers worldwide complain about severe yield losses caused by Potato virus Y (PVY). Therefore, PVY along with Potato virus Y belongs to the most important potato viruses. There are three main strains of PVY: PVY^O^, PVY^N^ and PVY^C^. However, also recombinant forms exist such as PVY^N^Wilga and PVY^NTN^, both of which increase in importance due to their potential to displace the non-recombinant strains at a high percentage. They appear also in mixed infections. In recent years PCR and qPCR assays were developed to differentiate PVY isolates. In order to identify PVY isolates by PCR often large amplicons have to be generated which requires the input of expensive enzymes. On the other hand, qPCR assays until now do not allow the differentiation between PVY^N^Wilga and PVY^NTN^.For the discrimination between PVY^O^/PVY^N^Wilga and PVY^N^/PVY^NTN^ a qPCR assay was developed, which allows the differentiation and highly efficient quantification of both strains and recombinants, respectively. For this purpose dual-labeled hydrolysis probes tagged with different fluorophores were designed. The assay is suitable for many different applications, for example safety research on genetically modified (GM) potato plants. The goal of this research is to determine whether genetic modification causes changes in resistance to viruses. Two different GM cultivars were examined for signs of altered resistance to an infection with PVY in comparison to their near-isogenic lines and three reference cultivars. Reference cultivars are included to determine the baselines for resistance and thus to be able to decide if the changes could represent a biological risk. The plants to be investigated were mechanically inoculated with PVY^N^Wilga or PVY^NTN^ and analyzed by means of the developed assay after two weeks. The results of the experiment indicate that the differences in virus titer between the reference cultivars are higher than between the GM potatoes and their isogenic lines. Therefore, in our experiments the GM potato plants showed no alteration in PVY resistance to neither one of the tested strains.Since Myzus persicae is one of the most important vectors transmitting PVY, the developed assay will also be applied to the quantification of PVY particles in aphids. The displacement of PVY^O^ and PVY^N^ by PVY^N^Wilga and PVY^NTN^ may be due to a difference in efficiency of transmission by M. persicae. Therefore, the objective is to test whether more virus particles of the recombinant forms in comparison to the non-recombinant strains PVY^O^ and PVY^N^ bind in the stylets of M. persicae. A third possible application of the developed assay may be of interest in potato breeding. The exact quantification of PVY particles in plants allows the classification of resistance in potato plants. It is possible to estimate whether a resistance is extreme or not. Extreme resistance is characterized by the absence or presence of very low amounts of virus particles in plants several days after inoculation. When testing the plants for PVY infection by ELISA, often unspecific reactions occur which makes it difficult to differentiate between plants weakly infected and plants very weakly infected. An exact quantification of the PVY titer gives more certainty for the determination of the resistance type.In conclusion, the developed assay is an efficient and low-cost method that allows the differentiation and quantification of PVY^O^/PVY^N^Wilga on the one hand and PVY^N^/PVY^NTN^ on the other hand with high throughput. The method can be utilized for a wide range of applications in potato research.

Every year potato growers worldwide complain about severe yield losses caused by Potato virus Y (PVY). Therefore, PVY along with Potato virus Y belongs to the most important potato viruses. There are three main strains of PVY: PVY^O^, PVY^N^ and PVY^C^. However, also recombinant forms exist such as PVY^N^Wilga and PVY^NTN^, both of which increase in importance due to their potential to displace the non-recombinant strains at a high percentage. They appear also in mixed infections. In recent years PCR and qPCR assays were developed to differentiate PVY isolates. In order to identify PVY isolates by PCR often large amplicons have to be generated which requires the input of expensive enzymes. On the other hand, qPCR assays until now do not allow the differentiation between PVY^N^Wilga and PVY^NTN^.For the discrimination between PVY^O^/PVY^N^Wilga and PVY^N^/PVY^NTN^ a qPCR assay was developed, which allows the differentiation and highly efficient quantification of both strains and recombinants, respectively. For this purpose dual-labeled hydrolysis probes tagged with different fluorophores were designed. The assay is suitable for many different applications, for example safety research on genetically modified (GM) potato plants. The goal of this research is to determine whether genetic modification causes changes in resistance to viruses. Two different GM cultivars were examined for signs of altered resistance to an infection with PVY in comparison to their near-isogenic lines and three reference cultivars. Reference cultivars are included to determine the baselines for resistance and thus to be able to decide if the changes could represent a biological risk. The plants to be investigated were mechanically inoculated with PVY^N^Wilga or PVY^NTN^ and analyzed by means of the developed assay after two weeks. The results of the experiment indicate that the differences in virus titer between the reference cultivars are higher than between the GM potatoes and their isogenic lines. Therefore, in our experiments the GM potato plants showed no alteration in PVY resistance to neither one of the tested strains.Since Myzus persicae is one of the most important vectors transmitting PVY, the developed assay will also be applied to the quantification of PVY particles in aphids. The displacement of PVY^O^ and PVY^N^ by PVY^N^Wilga and PVY^NTN^ may be due to a difference in efficiency of transmission by M. persicae. Therefore, the objective is to test whether more virus particles of the recombinant forms in comparison to the non-recombinant strains PVY^O^ and PVY^N^ bind in the stylets of M. persicae. A third possible application of the developed assay may be of interest in potato breeding. The exact quantification of PVY particles in plants allows the classification of resistance in potato plants. It is possible to estimate whether a resistance is extreme or not. Extreme resistance is characterized by the absence or presence of very low amounts of virus particles in plants several days after inoculation. When testing the plants for PVY infection by ELISA, often unspecific reactions occur which makes it difficult to differentiate between plants weakly infected and plants very weakly infected. An exact quantification of the PVY titer gives more certainty for the determination of the resistance type.In conclusion, the developed assay is an efficient and low-cost method that allows the differentiation and quantification of PVY^O^/PVY^N^Wilga on the one hand and PVY^N^/PVY^NTN^ on the other hand with high throughput. The method can be utilized for a wide range of applications in potato research.

Purpose: Chitosan, a natural biopolymer with antifungal and eliciting properties is able to reduce postharvest decay of table grapes. Anti-fungal and anti-microbial effects of essential oils are the result of many compounds acting synergistically. In this study, the effectiveness of Thymus essential oil (TEO) and chitosan to control postharvest decay and quality of ‘Shahroudi’ table grape was investigated. Research Method: Grapes treated by 0.5% and 1% (w/v) solution of chitosan, 150 and 300 µl l-1 Thymus essential oil and their combination (untreated fruit were as control). At first chitosan solution prepared then Thymus essential oil was added it in combination solution. Harvested grapes were packed in 200g bags and stored at 0±2 ◦C and 90% ± 5 RH for 90 days. Findings: Differences in weight loss, color change, ripening, sensory quality and decay between grapes treated with chitosan and TEO and control fruit suggested that TEO and chitosan were both suitable coatings. Moreover, the sensory analyses revealed beneficial effects in terms of delaying rachis browning and dehydration and maintenance of the visual characteristics of the grape without detrimental effects on taste or flavors. Research limitations: It had no limitation to report. Originality/Value: TEO and chitosan might have good effects in reducing postharvest fungal rot and maintaining the quality of ‘Shahroudi’ table grapes which proved to be much more effective than TEO.

The stylet penetration behavior of aphids when feeding on plants is associated with virus acquisition and inoculation. Aphidius gifuensis (Ashmead) is a primary endoparasitoid of Myzus persicae (Sulzer) which is the most efficient vector of plant viruses. Information about the effects of parasitoid on aphid and virus transmission can provide an essential foundation for designing effective biological control strategies. This study aimed to investigate the effects of A. gifuensis on the feeding behavior and potato virus Y (PVY) transmission ability of M. persicae. The results showed that after M. persicae was parasitized by A. gifuensis, the duration of the first probe significantly decreased. Additionally, A. gifuensis exerted remarkable effects on aphid feeding in phloem ingestion. The contribution of the E1 waveform to the phloem phase was significantly higher in all parasitized aphids than in the control group. Although the time of infestation increased for parasitized aphids, the total duration of phloem sap ingestion decreased. Interestingly, the percentage of time M. persicae spent in the xylem and phloem phases only changed significantly on day 5. The percent transmission of PVY by the aphids parasitized on day 5 was lower than that in the control, but no significant differences were detected. The significance of this work is the demonstration that A. gifuensis can impede the feeding behavior of M. persicae, which sheds light on the biological basis of A. gifuensis as a natural enemy, but unfortunately does not provide an immediate solution for disrupting the transmission of PVY.

The interactions among plant viruses, insect vectors, and host plants have been well studied; however, the roles of insect viruses in this system have largely been neglected. We investigated the effects of MpnDV infection on aphid and PVY transmission using bioassays, RNA interference (RNAi), and GC-MS methods and green peach aphid (Myzus persicae (Sulzer)), potato virus Y (PVY), and densovirus (Myzus persicae nicotianae densovirus, MpnDV) as model systems. MpnDV increased the activities of its host, promoting population dispersal and leading to significant proliferation in tobacco plants by significantly enhancing the titer of the sesquiterpene (E)-β-farnesene (EβF) via up-regulation of expression levels of the MpFPPS1 gene. The proliferation and dispersal of MpnDV-positive individuals were faster than that of MpnDV-negative individuals in PVY-infected tobacco plants, which promoted the transmission of PVY. These results combined showed that an insect virus may facilitate the transmission of a plant virus by enhancing the locomotor activity and population proliferation of insect vectors. These findings provide novel opportunities for controlling insect vectors and plant viruses, which can be used in the development of novel management strategies.

Potato virus Y (PVY) is an economically important and reemerging potato pathogen in North America. PVY infection reduces yield, and some necrotic and recombinant strains render tubers unmarketable. Although PVY(O) is the most prevalent strain in the United States, the necrotic and recombinant strains PVY(NTN) and PVY(N:O) are becoming more widespread. Infection rates in aphid-inoculated (Myzus persicae (Sulzer)) and mechanically inoculated plants were compared across two potato genotypes ('Yukon Gold' and A98345-1), three PVY strains (PVY(O), PVY(N:O), and PVY(NTN)), and two growth stages at inoculation (pre- and postflowering). Susceptibility of genotypes was measured as infection rate using a double-antibody sandwich-enzyme-linked immunosorbent assay; virus titer and tuber mass also were recorded from the infected plants. Yukon Gold generally was more susceptible than A98345-1 to all three PVY strains, especially following mechanical inoculation. Within genotypes, Yukon Gold was most susceptible to PVY(O) and A98345-1 was most susceptible to PVY(N:O). Plants exhibited age-based resistance, with both genotypes showing higher susceptibility at the pre- than postflowering stage. The overall ranking pattern of virus titer in infected plants was PVY(O) > PVY(NTN) > PVY(N:O); across all three strains, infected Yukon Gold had higher titer than infected A98345-1 plants. Yukon Gold plants had lower tuber mass than A98345-1 when infected, and there were differences between the two inoculation methods in regard to tuber mass for the three stains. The results showed differences in infection response between inoculation methods and as a function of genotype, strain, inoculation stage, and their interactions. These factors should be considered when screening genotypes for resistance.

Nucleotide and amino acid sequences of the helper component protease (HC-Pro) and the coat protein (CP) of two Hungarian Potato virus Y (PVY) isolates, differing in aphid transmissibility were determined. Isolate PVY-5 belongs to the common “O” strain (PVY O ), whereas isolates PVY-98 and PVY-111 belong to the “N” (PVY N ) and the PVY-NTN and PVY-H to the “NTN” (PVY NTN ) strains, respectively. The PVY-5 isolate varied significantly from the others in aphid transmission and in the ability to systemically infect potato plants. To elucidate whether these differences were due to mutations affecting known functional motifs, the corresponding cistrons of the two proteins were sequenced and aligned. Our analysis showed that none of the well-known motifs, responsible for aphid transmission in the two proteins had been affected. However, the defective isolate had two natural mutations in the HC-Pro in the vicinity of the PTK motif, and a number of mutations in the CP, distributed both in the N-terminus and the central region. As these two proteins are the only known viral participants in the aphid transmission mechanism, it is likely that some of the observed mutations might be involved in this process. Thus, our results indicate that other, previously unidentified sequences or factors may influence virus-vector interactions and transmission of PVY.

Chapter 10 - Synergism in plant–virus interactions: A case study of CMV and PVY in mixed infection in tomato

Aphid species that test positive for plant viruses in reverse transcription‐PCR (RT‐PCR) analysis are not necessarily vectors. This is because virus RNA can also be detected in non‐vector aphid species using this method. Potato virus Y (PVY) has been previously detected using RT‐PCR from three common weed‐infesting alate aphid species, Aphis fukii Shinji, Aphis oenotherae Oestlund, and Capitophorus hippophaes javanicus Hille Ris Lambers, trapped in potato fields in Hokkaido, northern Japan. However, these three taxa are not known as PVY vectors, and it remains unclear whether they acquired PVY from their respective host plants or other common weeds. Therefore, we conducted two experiments: (i) transmission experiments of these aphids using Myzus persicae (Sulzer), a species widely regarded as the most efficient PVY vector, as a reference species, and (ii) virus susceptibility experiments of typical host plant species of the three aphid species and other common weed species in and around potato fields in Hokkaido. The transmission experiments showed that the PVY‐transmission efficiency of A . fukii and A. oenotherae was not significantly different from that of M. persicae . In contrast, C. hippophaes javanicus did not transmit PVY. The estimated maximum transmission efficiency by one aptera was 7.5%. Mechanical inoculations and field sampling revealed that the tested weed species were not susceptible to PVY. These findings suggest that A . fukii and A. oenotherae serve as common and efficient PVY vectors in potato fields in Hokkaido, despite their individual transmission efficiency being < 7.5%. They likely acquire PVY from infected potato plants and/or unidentified reservoirs. These novel insights can advance our understanding of PVY epidemiology in Japan and contribute to the development of more effective vector‐based control strategies against PVY.

Further studies on the transmission of plant viruses by different forms of aphids

Potato virus Y (PVY) is a common pathogen affecting agricultural production worldwide and is mainly transmitted by Myzus persicae in a non-persistent manner. Insect-borne plant viruses can modify the abundance, performance, and behavior of their vectors by altering host plant features; however, most studies have overlooked the fact that the dynamic progression of virus infection in plants can have variable effects on their vectors. We addressed this point in the present study by dividing the PVY infection process in tobacco into three stages (early state, steady state and late state); delineated by viral copy number. We then compared the differential effects of PVY-infected tobacco (Nicotiana tabacum) plants on the host selection and feeding behavior of M. persicae. We used Y-shaped olfactory apparatus and electrical penetration graph (EPG) methods to evaluate host selection and feeding behavior, respectively. Interestingly, we found that PVY-infected plants at the steady state attracted more aphids than healthy plants, whereas no differences were observed for those at the early and late states. In terms of feeding behavior, intracellular punctures (closely related to PVY acquisition and transmission) were more abundant on PVY-infected tobacco plants at the early and steady states of infection than in uninfected plants. These results indicate that PVY-infected host plants can alter the host selection and feeding behavior of aphids in a stage-dependent manner, which is an important consideration when studying the interactions among host plants, viruses, and insect vectors.