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11: Papaya Ringspot

Tennant, P.; Fermin, G. CABI PDF

11

Papaya Ringspot

Gustavo Fermin,1* Melaine Randle2 and Paula Tennant2,3

Instituto Jardín Botánico de Mérida, Faculty of Sciences,

Universidad de Los Andes, Mérida, Venezuela; 2Biotechnology

Centre, The University of the West Indies, Mona Campus,

Jamaica; 3Department of Life Sciences, The University of the

West Indies, Mona Campus, Jamaica

1

11.1  Introduction: Disease and

Symptoms

Papaya ringspot disease caused by Papaya ringspot virus (PRSV) is perhaps the most serious disease of papaya (Tennant et al.,

2007; Tripathi et al., 2008), a crop that is well adapted to intensive commercial orchards and backyard stands in tropical and subtropical regions (Purcifull et al., 1984). High prevalence of the disease has been noted in the

Caribbean islands, the USA (Florida, Texas and Hawaii), South America, the Philippines,

Taiwan, Thailand and the southern region of China (Gonsalves, 1998) as far back as the

1930s (Fermin et al., 2010). The aetiological agent exists as two serologically indistinguishable biotypes (Purcifull et al., 1984;

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18: Viruses affecting tropical and subtropical crops: future perspectives

Tennant, P.; Fermin, G. CABI PDF

18

Viruses affecting tropical and subtropical crops: future perspectives

Gustavo Fermin1* and Paula Tennant2

Instituto Jardín Botánico de Mérida, Faculty of Sciences,

Universidad de Los Andes, Mérida, Venezuela; 2Department of Life Sciences, The University of the West Indies, Mona

Campus, Jamaica

1

Fifteen chapters spanned a range of highly divergent taxonomic groups of plant viruses, their effects on host phenotypes and implications for the management of virus diseases in tropical and subtropical agriculture. Although the diseases covered can be grouped under two categories, namely major (or traditional) virus diseases versus minor diseases of less economic significance and/or limited geographic distribution, all are considered equally important with respect to maintaining the sanitary status and food security of a region. Some of the diseases covered in this book are initiated by infections with a single virus pathogen that is transmitted by only one or two vector species. The aetiology is less conclusive for others. At the extreme, there are diseases elicited by a complex of different viruses or by a complex involving a number of different viruses along with different groups of insects. Papaya ringspot is an example of a disease caused by a virus with a narrow host range, infecting only papaya, its wild relatives and members of two or so other plant families under natural conditions.

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3: Wheat Dwarf

Tennant, P.; Fermin, G. CABI PDF

3

Wheat Dwarf

Isabelle Abt1,2 and Emmanuel Jacquot1*

INRA-Cirad-SupAgro Montpellier, Montpellier, France;

Bayer S.A.S./Bayer CropScience, Lyon, France

1

2

3.1  Introduction

Cereals can be infected by a vast range of pathogens of which Wheat dwarf virus (WDV, family Geminiviridae, genus Mastrevirus), the aetiological agent of wheat dwarf disease

(WDD), is one of the most damaging of all.

WDV is exclusively transmitted from plant to plant by leafhoppers. Very few options are available for the farmers to control this pathogen in the field. Indeed, the lack of genetic resistance against WDV in cereal germplasm, the rare sources of genetic tolerance and the absence of anti-viral molecules lead to the use of indirect management methods such as the modification of cultivation practices and/ or use of insecticides to protect cereal crops from WDV infections.

Even though WDD can be associated with important economical and agronomical impacts, scientific knowledge on this pathosystem and the epidemiology of the disease are still limited. Only a few studies on WDV have been published after three decades between the first report of wheat dwarf-like symptoms back in the 1960s and the description of WDD outbreaks in the 1990s (e.g. Vacke,

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7: Potato Mosaic and Tuber Necrosis

Tennant, P.; Fermin, G. CABI PDF

7

Potato Mosaic and Tuber Necrosis

 Mohamad Chikh-Ali and Alexander V. Karasev*

 Department of Plant, Soil and Entomological Sciences,

 University of Idaho, Moscow, Idaho, USA

7.1  Introduction: The Aetiologic

Agent, Disease Symptoms,

Distribution and Economic

Importance

Potato virus Y (PVY), the aetiological agent of potato mosaic or potato tuber necrotic ringspot disease (PTNRD), is the most economically important and devastating virus infecting potato crops worldwide (Singh et al., 2008;

Gray et al., 2010; Karasev and Gray, 2013b).

PVY is the type species of the genus Potyvirus, family Potyviridae, the second largest family of plant viruses after Geminiviridae.

The virus has a single-stranded positive-­sense

RNA genome of about 9.7 kb with a covalently linked VPg protein at the 5′ terminus and a poly-A tail at the 3′ terminus (Adams et al.,

2012). The genome RNA of PVY has two non-­ translated regions, 5′ and 3′, flanking a single open reading frame that encodes for a large polyprotein. Upon translation, the polyprotein is co- and/or post-translationally cleaved by three viral-specific proteases, P1, HC-Pro and

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12: Tomato Spotted Wilt

Tennant, P.; Fermin, G. CABI PDF

12

Tomato Spotted Wilt

Tsung-Chi Chen1,2 and Fuh-Jyh Jan3,4*

Department of Biotechnology, Asia University, Wufeng,

Taichung, Taiwan; 2Department of Medical Research, China

Medical University Hospital, China Medical University,

Taichung, Taiwan; 3Department of Plant Pathology, National

Chung Hsing University, Taichung, Taiwan; 4Agricultural

Extension Center, National Chung Hsing University,

Taichung, Taiwan

1

12.1  Introduction

Tomato spotted wilt disease was first reported in Australia in 1915 and later identified as a virus-infecting disease caused by Tomato spotted wilt virus (TSWV) (Brittlebank, 1919;

Samuel et al., 1930). Initially, geographically distinct TSWV isolates were classified in a particular ‘group’ on the basis of particle morphology, host range and transmission by thrips (Matthews, 1982). Until Impatiens necrotic spot virus (INSV) was discovered (Law and Moyer, 1990), this group was proposed as the genus Tospovirus and assigned to the family Bunyaviridae by the International

Committee on Taxonomy of Viruses in 1991 based on virion morphology and genome organization (Francki et al., 1991). Currently, tospoviruses have become a worldwide problem. Some tospoviruses, such as TSWV, Iris yellow spot virus (IYSV), Groundnut bud necrosis virus (GBNV) and Watermelon silver mottle virus (WSMoV), are of global importance. TSWV is the most important tospovirus with a worldwide distribution that includes

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