Transmission Of Plant Viruses Research Articles

Mite Transmission of Plant Viruses

Mite Transmission of Plant Viruses

A Threshold for Timing Applications of IGRs to Manage the Silverleaf Whitefly and Irregular Ripening on Tomato

The silverleaf whitefly, Bemisia argentifolii Bellows & Perring, has been the major pest of tomatoes in South Florida since 1988 (Schuster et al. 1989). The insect causes losses indirectly through the transmission of plant viruses, including Tomato mottle virus and Tomato yellow leaf curl virus in Florida (Simone et al. 1990, Polston et al. 1999). Feeding, primarily by nymphs, has been associated with an irregular ripening (IRR) disorder of fruit (Schuster et al. 1990, Schuster 2002). The disorder is characterized externally by inhibited or incomplete ripening of longitudinal sections of fruit and internally by an increase in the amount of white tissue. No foliar symptoms are apparent. This document is ENY705, a publication of the Entomology and Nematology Sciences Department, Florida Cooperative Extension Serivce, IFAS, University of Florida. Publication date: March 2004.
 ENY705/IN499: A Threshold for Timing Applications of Insecticides to Manage the Silverleaf Whitefly and Irregular Ripening on Tomato (ufl.edu)

Green Peach Aphid, Myzus persicae (Sulzer) (Insecta: Hemiptera: Aphididae)

The green peach aphid, Myzus persicae (Sulzer), is found throughout the world, including all areas of North America, where it is viewed as a pest principally due to its ability to transmit plant viruses. In addition to attacking plants in the field, green peach aphid readily infests vegetables and ornamental plants grown in greenhouses. This allows high levels of survival in areas with inclement weather, and favors ready transport on plant material. When young plants are infested in the greenhouse and then transplanted into the field, fields will not only be inoculated with aphids but insecticide resistance may be introduced. These aphids also can be transported long distances by wind and storms. This document is EENY-222, one of a series of Featured Creatures from the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: July 2001. Revised: July 2004. 
 EENY222/IN379: Green Peach Aphid, Myzus persicae (Sulzer) (Insecta: Hemiptera: Aphididae) (ufl.edu)

An incubator useful for culturing Olpidium brassicae for transmission of plant viruses

An incubator useful for culturing Olpidium brassicae for transmission of plant viruses

Seed Transmission of Plant Viruses

The chapter discusses on the wide range of aspects relating to seed transmission but with special reference to the more recent developments in this field. One of the most interesting characteristic of plant viruses' relationships to their host plants is the high degree of protection possessed by embryos of seeds against invasion by viruses that affect the mother plant. Despite this protection, however, an appreciable number of viruses have been found to pass from one generation to the next through the medium of the seed. The great majority of instances, the seed offer a highly effective barrier to passage of most viruses from one generation to the next, and perpetuation of most of the more destructive viruses is still dependent on repeated infection of successive generation of plants through the agency of natural vectors. The weight of evidence available at the present time appears to indicate that transmission of viruses through the embryo may be influenced and conditioned by a number of factors, and that no single factor can be used to explain all seed transmission or lack of it. However, it would appear that one of the determining factors involved in seed transmission of viruses, in the great majority of cases, is the ability of virus to infect male and female gametophytes. Whether this is determined by the ability of virus to invade meristematic tissue and thus enter the gametes in early stages of development, as much evidence indicates, or whether invasion is determined in part by susceptibility of the gametophytic generation to infection, is difficult to determine.

Beetle Transmission of Plant Viruses

Although the majority of plant viruses are transmitted by insects with sucking mouthparts, some viruses are transmitted by insects with biting mouthparts. Of the insects with biting mouthparts that transmit viruses, the beetles are the most important vectors. Viruses transmitted by beetles apparently cannot be transmitted by insects with sucking mouthparts. Until recently it has been generally assumed that when a biting insect behaves as a vector, it only does so by carrying infective sap from diseased to healthy plants on its mouthparts. However, when a beetle is an efficient vector and retains virus up to 20 days as the cucumber beetle does with squash mosaic virus, some additional mechanism of transmission probably is involved. This chapter brings together the various aspects of beetle transmission of plant viruses. Viruses transmitted by beetles have many properties in common. Usually, they are relatively stable, develop a high titer in infected plants, can be readily transmitted by manual inoculation, have spherical or polyhedral particles from 25 to 30 mp in diameter, and are highly antigenic. Host ranges and symptoms are usually not correlated with any specific features of the virus particles or with their vectors. The beetle-transmitted viruses can be divided into two groups depending on the length of time the viruses are retained by their vectors. The larger group consists of the viruses that are retained by their vectors for a prolonged period of time. The other group is made up of those viruses that are retained by their vectors for short periods of time, usually 24-48 hours. Only beetles in the family, Chrysomelidae, commonly called leaf beetles, have been shown to transmit plant viruses. All but two of the beetles belong in two subfamilies-Galerucinae (Galerucine leaf beetles) and Halticinste (flea beetles).

Application of Scanning Microscopy in the Study of Virus Transmission of Aphids

The scanning electron microscope was used in conjunction with the transmission electron microscope to study stylet morphology and the role of stylets of the green peach aphid in plant virus transmission. The morphology of the stylets generally agreed with earlier descriptions of these parts obtained with the transmission electron microscopy. A considerable variation seemed to exist in the extent and regularity of ridges observed in different individuals, especially among apterous adults and nymphs. Surface contamination of stylets as well as of the bristle area of the labium could be detected. The possible role of these contaminants in plant virus transmission is discussed. Working near the limit of resolution of the scanning electron microscope, visualization of two types of plant virus particles was attempted. Dipping aphid stylets in suspensions of purified virus did not lead to subsequent detection of these particles on the stylets with the scanning electron microscope. The scanning microscope is evaluated for its possibilities in the study of plant virus transmission by insects.

Reaction of Tomato Varieties and Breeding Lines to Aphids

Abstract The potato aphid (Macrosiphum euphorbiae) is a common insect pest of tomatoes. This insect damages the plants by sucking the sap from the leaves and by transmitting plant viruses The severity of aphid infestations on tomatoes varies from season to season and within a season. They are generally most severe during periods of cool weather.

Reaction of Tomato Varieties and Breeding Lines to Aphids

Abstract The potato aphid (Macrosiphum euphorbiae) is a common insect pest of tomatoes. This insect damages the plants by sucking the sap from the leaves and by transmitting plant viruses The severity of aphid infestations on tomatoes varies from season to season and within a season. They are generally most severe during periods of cool weather.

Transmission of plant viruses by dodder

MECHANICS OF VIRUS TRANSMISSION BY DODDER In 1940 Bennett discovered that a virus could be transmitted from an infected to a healthy plant through a bridging dodder that was parasitizing both plants. Since then numerous workers have shown that many viruses are transmissible. The subject has been reviewed by Mooi-Bok (1949), Sibilia (1951), Bawden (1956, 1964), and Fulton (1964). Transmission probably involves an association of dodder and host cells, and directional movement of nutrients. It has long been known that dodder haustoria establish cellular connections with the host plant. Thoday (1911) found that the protoplasts of dodder and host phloem cells are in close association but do not appear to fuse. Bennett (1944b) hypothesized that dodder acquires viruses with the food materials from the phloem of the host. His studies of dodder stems inoculated with beet curly-top virus or with cucumber mosaic virus indicated that after entering the dodder a virus moves more rapidly toward growing points than in the opposite direction. He suggested that yellows-type viruses move from the phloem of the dodder into the phloem of the healthy host by temporary reversals of phloem nutrient flow and that mosaic-type viruses move from the parenchyma of the haustorium to that of the host through plasmodesmatal strands or from possible naked protoplasmic connections of dodder and host, as well as through the phloem. Bennett (1956) proposed that the above idea of temporary-reversalof-flow fits well with the theory that materials in the phloem move ". . . by mass flow of liquid content of the phloem from the regions of carbohydrate supply toward regions of food utilization." Cochran (1946) found that consistent transmission of tobacco mosaic virus could be achieved only by pruning the dodder and shading the healthy host while keeping the infected host in bright light; Bennett (1956) suggested that this forced a temporary reversal of phloem nutrient flow. Canova (1955) observed that Cuscuta epithymum Murr. acquired beet-yellows virus but did not transmit it, and Bennett (1960) found the same to be true for C. californica Hooker &

Plant Virus-Vector Relationships

Publisher Summary The chapter discusses a fairly comprehensive account of the main factors in relationships between plant viruses and their vectors. The vectors occur among almost every kind of organism that feeds upon plants and that the relationships consist of all grades from a purely mechanical contamination to a close biological relationship between virus and vector. Mechanical transmission of plant viruses in this context refers to a mode of transfer, in which there is no evidence of any biological relationship between virus and vector. The question as to whether some aphid borne viruses are mechanically transmitted is discussed in the chapter dealing with aphid-virus relationships, and with one exception, this chapter is concerned with virus transmission by insects with biting mouthparts. The methods of mechanical transmission dealt with, so far, have been concerned only with external contamination; there are, however, other examples of mechanical transmission in which more than this is involved. Biological transmission indicates a definite relationship between plant virus and insect vector. It has been seen something of this in the discussion of the viruses of potato leaf roll and Sonchus yellow vein and their aphid vectors, but it is in regard to some of the leafhopper-borne viruses that ones knowledge of this phenomenon is the greatest. It could be that in considering the vector transmission of plant viruses, observing the gradual extension of the host range of the viruses by long-continued association of insect and plant, with transmission an incidental factor arising out of this long-continued association.

Transmission of cabbage mosaic virus by green peach aphids—Stylet transmission studies

An analysis was made of the experimental procedures that have been used to determine the function of the tips of the stylets in the transmission of nonpersistent plant viruses. The virus used was cabbage mosaic, and the vector was the green peach aphid, Myzus persicae (Sulzer). To prepare the stylets for treatment, the aphids were first anesthetized with CO 2 and then the labium was manipulated to expose the stylet tips. After the stylets had been exposed, both ultraviolet (UV) irradiation and immersion of the stylets in 0.25% formalin were used to reduce or eliminate inoculativity. Anesthetized aphids tended to probe longer than did unanesthetized ones, and since a time limit was set for the duration of any single probe, more anesthetized aphids had their probes artificially terminated than did the unanesthetized controls. When this factor was accounted for (by using the data from aphids that naturally terminated their acquisition probes), none of the following preacquisition treatments reduced the probability of acquisition and transmission of virus: anesthetization, anesthetization and manipulation, irradiation of the stylet tips with UV, or treatment of the stylet tips with 0.25% formalin. These same treatments were used after acquisition, and each reduced the probability of transmission. The effect on transmission was as follows: no treatment < anesthetization < manipulation < stylet irradiation < stylet treatment with 0.25% formalin. Some, but not all, of the reduction in transmission due to the treatments, especially in connection with UV irradiation, could be attributed to treatment-induced changes in feeding behavior. The evidence from the various experiments and from serial transmission trials was consistent with the hypothesis that transmissible virus was being carried in a small piece of saliva at the tip of the stylets.

Initial infection processes by certain mechanically transmitted plant viruses

Nicotiana sylvestris Spegaz. and Comes, and Phaseolus vulgaris L. var. “Scotia” leaves developed a uniformly low number of local lesions after being mildly wounded and inoculated by immersion in preparations of partially purified tobacco necrosis virus (TNV) and common tobacco mosaic virus (CTMV) or a yellow strain of the latter (YTMV). The wounding was mild enough so that the lesions were well separated and easily counted, and the virus concentration in the inoculum was high enough so that all sites were apparently saturated. Consequently the level of infection as measured by the number of local lesions that developed on the inoculated leaves usually depended on the time interval between wounding and inoculation, but not on the virus concentration. Phosphate buffer used as a control treatment reduced the receptivity of the hosts when it was applied immediately after wounding. CTMV reduced the receptivity of N. sylvestris to YTMV but not to TNV when the latter two were introduced without further wounding 10 minutes after inoculation with CTMV. Similarly on P. vulgaris, CTMV had no effect on the number of TNV lesions. The number of lesions produced by either CTMV or TNV was the same as it was if either virus was used alone. Similar trends in preferential receptivity of the two hosts after wounding were observed when TNV was introduced alone or in combination with other viruses. It is concluded that not all wounded cells exposed to inoculum result in the development of lesions even though the virus concentration is high enough so that virus must be present in or about most of these cells. Furthermore, the conditions necessary for initiation of infection after virus introduction in or around the wounded cells differ with the virus and the intrinsic reaction of the host.

Arthropod Transmission of Plant Viruses

Arthropod Transmission of Plant Viruses

Transmission of raspberry ringspot virus by Longidorus elongatus (de Man) (Nematoda: Dorylaimidae)

Two groups of economically important plant viruses, nepoviruses and tobraviruses, are transmitted through the longidorids, Trichodorus and Paratrichodorus. Nepoviruses and tobraviruses are taxonomically different from each other, but both have RNA genetic material and contain two different types of genomic RNAs. Nepovirus particles are spherical in shape, while tobraviruses are rod-shaped. Nepovirus species have a single coat protein (CP), which is assembled in multiple copies to form the virus particles. Longidorids have been reported as vectors of nepoviruses, while trichodorids serve as vectors of tobraviruses. Of the 41 species of nepoviruses, 13 are transmitted by 11 species of Xiphinema and 10 are transmitted by 11 species of Longidorus in different crops. Different species of Trichodorus and Paratrichodorus have been reported to transmit pepper ringspot virus, tobacco rattle virus, and pea early-browning virus in different countries. Plant-parasitic nematodes acquire virus particles during feeding by sucking cell sap with a stylet. Most of the plant-parasitic nematodes transmit plant viruses by feeding ectoparasitically near the root tip on the outside of the root surface. Among them, some nematodes induce galls at the infection site of root surface after completion of the feeding process. The transmission process of the plant viruses by nematodes are completed by different phases, such as ingestion, acquisition, adsorption, retention, release, transfer, and establishment. Efficient transmission from infected host plants to healthy host plants by nematode vectors is an important biological feature for the development of epidemics of plant diseases incited by viruses. Both the adult and juvenile stages of the nematode vectors are capable of transmitting the associated plant viruses. Virus transmission by a vector is often characterized by some degree of specificity. Specific relationships exist between the serologically distinct viruses and their vector nematode species. Specificity is largely determined by the virus CP and by an inherited ability of the nematode to retain virus particles at specific sites within its esophagus. Numerous studies suggest the involvement of a virus–ligand interaction in transmission specificity. The CP and its derivatives readthrough CP and minor CP and nonstructural proteins, such as a helper component or a transmission factor, are major viral determinants of transmission specificity. A number of virion-binding vector proteins have been identified as potential receptors.

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

Various forms of four aphid species were tested as vectors of potato virus Y (PVY) and cabbage virus B (CVB). Oviparous females of Macrosiphum euphorbiae (Thom.) and Brevicoryne brassicae (L.) transmitted the viruses as efficiently as did apterous viviparous females. In addition, PVY was transmitted by oviparae of Aulacorthum solani (Kltb.), and by males of M. euphorbiae. A “vector form specificity” seemed to exist in the transmission of PVY by fall and spring forms of Aphis nasturtii Kltb. The virus was transmitted by migratory forms such as gynoparae, males, and fundatrigeniae which during part of their life cycle live on virus-susceptible hosts, but not by oviparae and fundatrices, which spend their entire life cycle on the winter host. Thus vector form specificity in the transmission of PVY seems to be related to the host range of the aphid form.

Aphid transmission of plant viruses from the epidermis and subepidermal tissue: Myzus persicae (Sulzer)—Cucumber mosaic virus

Aphid transmission tests from the epidermis and exposed subepidermal tissues were conducted for five consecutive weeks after inoculation of the virus source plants with cucumber mosaic virus. The transmission rates from the subepidermal tissues (corrected for effects of exposure) were not significantly different from those of the epidermis. The hypothesis that transmission rates after brief feedings (epidermis) are generally higher than after prolonged feedings (during which aphid stylets penetrate into the subepidermal tissues), because of unequal distribution of virus in the tissues would not be consistent with the results obtained in this experiment.

Trapping study of some winged aphid vectors of plant virus diseases in Canterbury, New Zealand

Abstract Sticky aphid traps at crop height (26 in.) at each of three sites on the Canterbury Plains—Lincoln (altitude 36 ft above sea level), Darfield (600 ft), and Annat (1,100 ft)—were operated from October 1957 to September 1959. The most abundant aphid species trapped were Myzus persicae (Sulz.), Aulacorthum solani (Kltb.), Brevicoryne brassicae (L.), Cavariella aegopodii (Scop.), Rhopalosiphum padi (L.), and Capitophorus eleagni (D. Guerc.). The main period of aphid activity was early summer, when many species were present. Fewer aphid species were flying in autumn, though large flights of some species took place then. At each site there was very little aphid activity in mid-summer, probably as a result of the climatic conditions then prevailing throughout the area. There were large differences between the three Canterbury regions in the abundance of winged aphids in spring and early summer. The implications of these findings in relation to plant virus transmission are discussed.

A Pneumatic Laboratory Cage for Thysanoptera or other Arthropoda

Testing arthropods for their ability to transmit plant viruses depends on a satisfactory means of confining test specimens on plant hosts while excluding all other arthropods. This can be difficult with small, active insects such as the Thysanoptera. Screen or cloth capable of confining them must be of such fine mesh that adequate ventilation is prevented and condensation becomes a problem.

Negative Evidence against Passage of Whole Plant Virus Particles through Gut Wall in Aphid Vectors

IN transmission of so-called persistent aphid-borne plant viruses, an incubation period in the insect is generally observed. It is understood that this time is required for the virus circulation in the insect body. Virus taken up with the plant juice is supposed to penetrate the intestinal wall and later the wall of the salivary glands, transport of the virus from the former to the latter being brought about by the blood. This theory is supported strongly by the fact that blood from infective aphids injected into non-infective individuals has been shown to make the latter able to transmit the virus in question. This has been demonstrated for potato leaf roll virus1–3 and (Ossiannilsson, F., unpublished), beet yellow-net virus3, and pea enation mosaic virus4.