Advances in cowpea research , Advances in cowpea research , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Advances in cowpea research

Summary
1. Vector-borne pathogens and parasites can induce changes in the phenotypes of their hosts that influence the frequency and nature of host–vector interactions and hence transmission, as documented by both empirical and theoretical studies. To the extent that implications for transmission play a significant role in shaping the evolution of parasite effects on host phenotypes, we may hypothesize that parasites exhibiting similar transmission mechanisms – and thus profiting from similar patterns of interaction among hosts and vectors – will have correspondingly similar effects on relevant host traits. Here, we explore this hypothesis through a survey and synthesis of literature on interactions among plant viruses, their hosts, and insect vectors.

2. Insect-vectored plant viruses that differ in their modes of transmission benefit from different patterns of interaction among host plants and vectors. The transmission of persistently transmitted (PT) viruses requires that vectors feed on an infected host for a sustained period to acquire and circulate (and sometimes replicate) virions, then disperse to a new, healthy host. In contrast, non-persistently transmitted (NPT) viruses are effectively transmitted when vectors briefly probe infected hosts, acquiring virions, then rapidly disperse.

3. Based on these observations, and empirical evidence from our previous work, we hypothesized that PT and NPT viruses will exhibit different effects on aspects of host phenotypes that mediate vector attraction to, arrestment on and dispersal from infected plants. Specifically, we predicted that both PT and NPT viruses would tend to enhance vector attraction to infected hosts, but that they would have contrasting effects on vector settling and feeding preferences and on vector performance, with PT viruses tending to improve host quality for vectors and promote long-term feeding and NPT viruses tending to reduce plant quality and promote rapid dispersal.

4. We evaluated these hypotheses through an analysis of existing literature and found patterns broadly consistent with our expectations. This literature synthesis, together with evidence from other disease systems, suggests that transmission mechanisms may indeed be an important factor influencing the manipulative strategies of vector-borne pathogens, with significant implications for managing viral diseases in agriculture and understanding their impacts on natural plant communities.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2435.2012.02026.x

Transmission mechanisms shape pathogen effects on host-vector interactions: Evidence from plant viruses

▪ Abstract In this article we consider the role of epidemiological factors and transmission processes of insect-vectored viruses on the effectiveness of insecticides in a disease management program. We also discuss the use of insecticides within the broader framework of the chemical environment surrounding vectors, and how chemical-induced alterations in the behavior of vectors can influence transmission. Our analysis confirms the belief of Heathcote, who stated in 1973, that “no one method of control is likely to keep crops entirely free from virus infection and as many preventative measures should be taken as are economically justified.”

Management of plant viral diseases through chemical control of insect vectors.

Summary

Taxonomy:Turnip mosaic virus (TuMV) is a member of the genus Potyvirus (type species Potato virus Y) in the family Potyviridae. To date, TuMV is the only potyvirus known to infect brassicas. There are potyvirus isolates that appear serologically similar to TuMV when tested with polyclonal antisera that do not readily infect brassicas (Lesemann and Vetten, 1985).



 Physical properties: Virions are ≈ 720 × 15–20 nm flexuous rods (Fig. 1) and are composed of 95% coat protein (CP) and 5% RNA.




Figure 1. Electron micrograph of TuMV virions stained with methylamine tungstate. Courtesy of Colin Clay, HRI Wellesbourne.

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 Hosts: TuMV has been isolated from a wide range of crop and weed plant species. It is known to infect at least 318 species in over 43 dicot families, including Cruciferae, Compositae, Chenopodiaceae, Leguminosae and Caryophyllaceae and is also known to infect monocots. It has the broadest known host range in terms of plant genera and families of any potyvirus.



 Transmission: Aphid transmitted in the non-persistent manner, by at least 89 species, including Myzus persicae and Brevicoryne brassicae.



 Useful website:http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/57010072.htm

Turnip mosaic virus and the quest for durable resistance.

Cowpea cultivars resistant to insect pests in world germplasm collection

Summary

The effectiveness of the synthetic pyrethroids deltamethrin and lambda-cyhal-othrin in preventing (i) aphid colonisation of four cowpea cultivars with different levels of aphid resistance and (ii) the introduction and subsequent spread of cowpea aphid-borne mosaic virus and cucumber mosaic virus was investigated under tropical field conditions.



Sprays of these pyrethroids eight days apart prevent aphid colonisation and within crop spread of virus by the colonising Aphis craccivora. However, neither deltamethrin nor lambda-cyhalothrin prevented the initial introduction of virus into the cowpea crop and, when incoming alate incidence was high, virus incidence was higher in the sprayed than in the unsprayed plots. In addition, the degree of aphid resistance of each cultivar affected secondary virus spread within the crop, with greatest spread in the most resistant cultivar.

Interaction between two synthetic pyrethroids and the spread of two non-persistent viruses in cowpea

Cowpea seed treatment with carbosulfan: potential for control of seedling pests

The ability of populations of adult apterous Aphis craccivora, A. gossypii and A. citricola to transmit the cowpea aphid-borne mosaic virus (CAMV) and cucumber mosaic virus (CMV) to cowpea was investigated. CMV was more readily transmitted than CAMV by all three aphid species, but was most readily transmitted by A. craccivora and A. citricola, with transmissions ranging from 64-71%. With CAMV, the infection level with A. gossypii was higher than with A. craccivora and both were more efficient than A. citricola, although the differences were not significant. With mixed infections of CAMV and CMV, there was a higher level of CAMV transmission using A. craccivora from sequential feeding when CMV-infected plants were fed on first followed by CAMV-infected plants, suggesting that cowpea plants were more prone to infection by CAMV when already infected by CMV

Julia M. F. Roberts

Papers

Interaction between two synthetic pyrethroids and the spread of two non-persistent viruses in cowpea

Cowpea seed treatment with carbosulfan: potential for control of seedling pests

The ability of Aphis craccivora, A. gossypii and A. citricola to transmit single and mixed viruses to cowpeas.