The transmission of insect-borne plant pathogens, including viruses, bacteria, phytoplasmas, and fungi depends upon the abundance and behavior of their vectors. These pathogens should therefore be selected to influence their vectors to enhance their transmission, either indirectly, through the infected host plant, or directly, after acquisition of the pathogen by the vector. Accumulating evidence provides partial support for the occurrence of vector manipulation by plant pathogens, especially for plant viruses, for which a theoretical framework can explain patterns in the specific effects on vector behavior and performance depending on their modes of transmission. The variability in effects of pathogens on their vectors, however, suggests inconsistency in the occurrence of vector manipulation but also may reflect incomplete information about these systems. For example, manipulation can occur through combinations of specific effects, including direct and indirect effects on performance and behavior, and dy...

Insect-Borne Plant Pathogens and Their Vectors: Ecology, Evolution, and Complex Interactions.

Banana diseases; including plantains and abaca , Banana diseases; including plantains and abaca , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Banana Diseases Including Plantains and Abaca

The complete nucleotide sequence of Chinese yam necrotic mosaic virus (CYNMV) was determined from cloned virus cDNA. The CYNMV genomic RNA is 8224 nucleotides in length, excluding the poly(A) tail, and contains one long open reading frame encoding a large polyprotein of 2620 amino acids. CYNMV has no counterpart to the P1 cistron and a short HC-Pro cistron located at the 5' side of the potyvirus genome. A full-length cDNA clone, pCYNMV, was assembled under the control of the cauliflower mosaic virus 35S promoter and the nopaline synthase terminator. Biolistic inoculation of Nagaimo plants with cDNA resulted in systemic necrotic mosaic symptoms typical of CYNMV infection. To our knowledge, this is the first report of the complete nucleotide sequence and construction of an infectious cDNA clone of a member of the genus Macluravirus.

Complete nucleotide sequence and construction of an infectious clone of Chinese yam necrotic mosaic virus suggest that macluraviruses have the smallest genome among members of the family Potyviridae

Epidemiology is the science of how disease develops in populations, with applications in human, animal and plant diseases. For plant diseases, epidemiology has developed as a quantitative science with the aims of describing, understanding and predicting epidemics, and intervening to mitigate their consequences in plant populations. Although the central focus of epidemiology is at the population level, it is often necessary to recognise the system hierarchies present by scaling down to the individual plant/cellular level and scaling up to the community/landscape level. This is particularly important for diseases caused by plant viruses, which in most cases are transmitted by arthropod vectors. This leads to range of virus-plant, virus-vector and vector-plant interactions giving a distinctive character to plant virus epidemiology (whilst recognising that some fungal, oomycete and bacterial pathogens are also vector-borne). These interactions have epidemiological, ecological and evolutionary consequences with implications for agronomic practices, pest and disease management, host resistance deployment, and the health of wild plant communities. Over the last two decades, there have been attempts to bring together these differing standpoints into a new synthesis, although this is more apparent for evolutionary and ecological approaches, perhaps reflecting the greater emphasis on shorter often annual time scales in epidemiological studies. It is argued here that incorporating an epidemiological perspective, specifically quantitative, into this developing synthesis will lead to new directions in plant virus research and disease management. This synthesis can serve to further consolidate and transform epidemiology as a key element in plant virus research.

https://www.mdpi.com/2223-7747/9/12/1768/pdf

The Epidemiology of Plant Virus Disease: Towards a New Synthesis.

https://escholarship.org/content/qt7fw8154c/qt7fw8154c.pdf?t=qaxpsk

A synthesis of virus-vector associations reveals important deficiencies in studies on host and vector manipulation by plant viruses.

Large cardamom (Amomum subulatum), an important spice crop grown in eastern sub-Himalayan mountains of India, is affected by a viral disease commonly known as ‘chirke’, which is characterised by light and dark green streaks on the leaf lamina. Although chirke has been known to affect large cardamom for over 50 years, its distribution in large cardamom growing regions and aetiology have remained unaddressed. In this study for the first time, distribution of chirke in the major large cardamom growing regions in India has been determined. North Sikkim and eastern region of Darjeeling hills were endemic region with average disease incidence of 19.2–35%, whereas, Mirik region of Darjeeling hills were free from the disease. Suckers, the commonly used planting material, were the major source for spread of the disease. The virus was sap transmissible to the popular large cardamom cultivars Golsey, Ramsey, Swaney and Varlangey and vectored by Rhopalosiphum maidis and Myzus persicae in a non-persistent manner. Flexuous virus particles measuring 625–650 × 12.5 nm were observed consistently associated with the diseased samples. Polyclonal antiserum to the purified virus showed serological affinity with a macluravirus, cardamom mosaic virus (CdMV) associated with a similar disease known as katte disease of small cardamom (Elettaria cardamomum) occurring in southern India. The 3 � terminal genome sequence (1776 nucleotides) of the virus was determined, which revealed a close sequence identity and phylogenetic relationships with the members of the genus Macluravirus. The deduced amino acid sequence of putative coat protein (CP) gene showed maximum similarity of 65.7% with the CdMV. Phylogenetic analysis based on CP and 3 � UTR showed that the virus was closer to Alpinia mosaic virus ,C dMV andChinese yam necrotic mosaic virus subclade. The results suggest that the virus associated with the chirke disease of large cardamom is a new species under the genus Macluravirus in the family Potyviridae for which the name large cardamom chirke virus (LCCV) is proposed.

Disease distribution and characterisation of a new macluravirus associated with chirke disease of large cardamom

Cardamom bushy dwarf virus (CBDV) causes foorkey disease of large cardamom (Ammomum subulatum Roxburgh) in the eastern sub-Himalayan mountains. Although the aphid Micromyzus kalimpongensis Basu (Hemiptera: Aphididae) is known as a vector of CBDV, its behavior in dissemination of CBDV has not been investigated. In the present study, M. kalimpongensis was observed to colonize in higher number on CBDV-infected large cardamom plants compared with the healthy plants in the several plantations in Sikkim and Darjeeling hills. The affinity of M. kalimpongensis to the diseased large cardamom plants was further confirmed in a contained field experiment with intact plant as well as in a laboratory bioassay with the plant extract, where significantly higher number of aphids settled on the diseased plants or extracts compared with the healthy counterparts. Aphids grown on CBDV-infected large cardamom plants had shortened nymphal period and increased longevity and fecundity compared with those grown on the healthy plants. In the contained field experiment, M. kalimpongensis migrated to the CBDV-infected plants, colonized there, acquired CBDV, and once the diseased plants withered, migrated to healthy plants, which eventually became diseased. Our results suggest a general pattern of spread of CBDV by M. kalimpongensis where CBDV-infected plants attract or arrest and stimulate emergence and migration of viruliferous aphids that otherwise are sedentary in the underground plant parts of large cardamom. To our knowledge, this is the first study that shows the influence of a plant virus from the family Nanoviridae in altering behavior of its insect vector that favors its dissemination.

Cardamom Bushy Dwarf Virus Infection in Large Cardamom Alters Plant Selection Preference, Life Stages, and Fecundity of Aphid Vector, Micromyzus kalimpongensis (Hemiptera: Aphididae).

Large cardamom chirke virus (LCCV), genus Macluravirus, family Potyviridae is an important constrain in large cardamom production in India. Purification of LCCV from large cardamom tissues is difficult and therefore immunodiagnostic reagents are not available. In the present study, we have successfully expressed coat protein (CP) gene of LCCV in Escherichia coli. The purification of expressed protein by Ni-NTA affinity chromatography was inefficient due to precipitation of protein during renaturation. We have optimized a simple, inexpensive and efficient method for purification of the expressed CP through gel extraction with 5 % SDS followed by renaturation in Milli-Q water, which resulted in high yield (4.7 mg/ml) and good quality of the protein. A higher titer (1:256,000) polyclonal antibody (PAb) to the recombinant CP was produced, which strongly recognized LCCV in crude leaf extract and showed minimal background reaction with the healthy leaf extract in enzyme linked immunosorbent assay (ELISA) and dot immunobinding assay (DIBA). The sensitivities of the ELISA and DIBA were 5 and 0.1 ng of expressed protein, respectively. Both the ELISA and DIBA were validated with 100 % accuracy in detecting LCCV in field samples. The PAb differentiated Cardamom mosaic virus, another close relative of LCCV. Our study is first to report highly efficient immunodiagnosis with PAb to E. coli expressed recombinant CP of a virus under the genus Macluravirus. The antigen expression construct and PAb developed in the present study will be useful in production of virus free planting materials of large cardamom.

/pdf/highly-efficient-immunodiagnosis-of-large-cardamom-chirke-5cinaektp5.pdf

Highly efficient immunodiagnosis of Large cardamom chirke virus using the polyclonal antiserum against Escherichia coli expressed recombinant coat protein

Few studies have been done on engineered antibodies for diagnosis of tospovirus infections. The present study was undertaken to develop a single-chain variable fragment (scFv) for specific diagnosis of infection by groundnut bud necrosis virus (GBNV), the most prevalent serogroup IV tospovirus in India. Heavy chain (372 nucleotide [nt]) and light chain (363 nt) variable region clones obtained from a hybridoma were used to make an scFv construct that expressed a ~29-kDa protein in E. coli. The scFv specifically detected GBNV in field samples of cowpea, groundnut, mung bean, and tomato, and it did not recognize watermelon bud necrosis virus, a close relative of GBNV belonging to tospovirus serogroup IV. This study for the first time demonstrated the application of a functional scFv against a serogroup-IV tospovirus.

Engineered single-chain variable fragment antibody for immunodiagnosis of groundnut bud necrosis virus infection

The genus, Babuvirus of the family Nanoviridae contains three virus species, Abaca bunchy top virus (ABTV), Banana bunchy top virus (BBTV) and Cardamom bushy dwarf virus (CBDV). In India, only two babuviruses, BBTV and CBDV are known to affect banana and large cardamom, respectively. BBTV, which causes bunchy top disease in banana, is a nationally important virus as it is widely prevalent in all the banana growing states including North-East region. Whereas, CBDV, which causes foorkey disease of large cardamom, is of regional importance as it is restricted only in the North-Eastern sub-Himalayan mountains. Early infection of these babuviruses cause 100% yield loss. Bunchy top of banana and foorkey disease of large cardamom are known in India for a long time and considerable information has been generated. This chapter summarises the biological and molecular properties of both the babuviruses occurring in India.

S. Vijayanandraj

Papers

Disease distribution and characterisation of a new macluravirus associated with chirke disease of large cardamom

Cardamom Bushy Dwarf Virus Infection in Large Cardamom Alters Plant Selection Preference, Life Stages, and Fecundity of Aphid Vector, Micromyzus kalimpongensis (Hemiptera: Aphididae).

Highly efficient immunodiagnosis of Large cardamom chirke virus using the polyclonal antiserum against Escherichia coli expressed recombinant coat protein

Engineered single-chain variable fragment antibody for immunodiagnosis of groundnut bud necrosis virus infection

Biology and Molecular Biology of Babuviruses Occurring in India