In this volume, the authors provide an excellent overview of how far the plant viral vector field has come. The discipline is no longer exclusively in the domain of academics—there is a small, but growing number of small biotechnology companies that exploit plant viruses as the platform for commercial innovation in crop improvement, industrial product manufacturing, and human and veterinary health care.

Although nematodes had long been suspected as vectors of soil borne plant diseases, unequivocal proof of their implication was not forthcoming until 1958 when Professor William Hewitt and his colleagues in California demonstrated experimentally that Xiphinema ~ was the vector of grapevine fanleaf virus. This opened up a new and exciting field in plant pathology and discoveries quickly followed of other nematode species associated with soil-borne diseases of many different crops and in several countries. After the initial enthusiasm of discovering new vectors and new viruses there followed a period of consolidation in which research workers sought answers to tantalising questions about the location of the virus within the nematode, the factors governing the close speci ficity between virus and vector; and more mundane but equally important and compelling questions about life cycles, geographical distribution, host relations, morphology and taxonomy. No other group of nematodes has attracted such a concentrated effort involv ing many different scientific specialisations and yielding so much progress in a relatively short time. The NATO Advanced Study Institute held at Riva dei Tessali, Italy, during 19 May to 2 June, 1974, provided the forum for a critical discussion of all aspects of biology of virus vector nema todes.

Molecular farming has been hailed as the "third wave" of genetically-modified organisms produced through biotechnology for the bio-based economy of the future. Unlike products of the first wave, such as herbicide resistant crop plants, which were perceived to benefit only the farmers who used them and the agrochemical companies who developed them, products of molecular farming are designed specifically for the benefit of the consumer. Such products could be purified from food or non-food organisms for a range of applications in industry, as well as animal and human health. Alternatively, the products of this technology could be consumed more directly in some edible format, such as milk, eggs, fruits or vegetables. There is a rapidly-growing interest Qn the part of the public as well as in the medical community in the role food plays in health, especially in the immunophysiological impact of food over and above the role of basic nutrition.

Stressing the key role vectors play spread of virus diseases, this volume represents the priorities in practical plant virus research and ways in which their control or management should be sought through an understanding of the practical and environmental aspects of the interactions of viruses with their vectors and their environment. It provides

Plant viruses cause many of the most important diseases threatening crops worldwide. Over the last quarter of a century, an increasing number of plant viruses have emerged in various parts of the world, especially in the tropics and subtropics. As is generally observed for plant viruses, most of the emerging viruses are transmitted horizontally by biological vectors, mainly insects. Reverse genetics using infectious clones--available for many plant viruses--has been used for identification of viral determinants involved in virus-host and virus-vector interactions. Although many studies have identified a number of factors involved in disease development and transmission, the precise mechanisms are unknown for most of the virus-plant-vector combinations. In most cases, the diverse outcomes resulting from virus-virus interactions are poorly understood. Although significant advances have been made towards understand the mechanisms involved in plant resistance to viruses, we are far from being able to apply this knowledge to protect cultivated plants from the all viral threats.The aim of this Special Issue was to provide a platform for researchers interested in plant virology to share their recent results. To achieve this, we invited the plant virology community to submit research articles, short communications and reviews related to the various aspects of plant virology: ecology, virus-plant host interactions, virus-vector interactions, virus-virus interactions, and control strategies. This issue contains some of the best current research in plant virology.

Plants viruses are increasingly being examined as alternative recombinant protein expression systems. Future development of plant virus expression vectors needs to focus on the most important economic hosts, namely cereals and legumes, to develop tools to aid breeding of such hosts and systems for edible vaccine production. Sunn hemp mosaic virus (SHMV) is a tobamovirus, which infects leguminous plants. This work reports on new SHMV-based viral vectors for high yield of target proteins in legumes. In the SHEC vector series, the coat protein gene of SHMV was substituted by a reporter gene. In the SHAC vector series, the coat protein was substituted by a reporter gene and the coat protein gene from another tobamovirus, tobacco mild green mosaic virus (TMGMV). Co-agroinoculation of SHEC/GFP with an RNA silencing suppressor resulted in high levels of local GFP expression by 3 days post inoculation. Co-agroinoculation with SHAC/GFP led to systemic fluorescence in 12-19 dpi. Foxtail mosaic virus (FoMV) is a species of the group Potexvirus, which infects cereal plants. A new viral vector series named FECT was constructed by eliminating the triple gene block and coat protein genes, reducing the viral genome by 29%. Interestingly, agroinoculation of the vector alone results in only slight transient expression, whereas co-inoculation with silencing suppressor genes allows for GFP expression of 40% total soluble protein. Full-sized HC and LC components of an anti-langerin IgG, each carried by a separate FECT vector, expressed and folded into immunologically functional antibody upon co-inoculation. This may prove a useful and environmentally safe vector for both transient expression and perhaps transgenic plants. Mountain cedar (Juniperus ashei) pollen causes severe allergies in Texas and the central USA. Jun a 1 is the dominant allergen protein of mountain cedar pollen and would be a good allergen vaccine candidate. Recombinant Jun a 1 was expressed in Nicotiana benthamiana using an agroinoculation-compatible tobacco mosaic virus vector and isolated in good quantity from the apoplast by vacuum infiltration (100 [mu]g/g leaf material). The recombinant protein samples were characterized. Pectate lyase activity was detected from plant extracts, suggesting the cause of severe necrotic reaction in plants.