A study of sugar beet growers' pest control decisions

The results of a survey of sugar beet growers are reported which provide subjective information on farmer perceptions of the hazard from pests and diseases on sugar beet, the control methods available and used, farmers' estimates of the costs and effect of controls, their objectives for pest control, and their attitudes to advice. In addition, objective information from research and field observations on losses and control methods is provided. The basis of pest control decisions and implications from comparisons of subjective and objective perceptions of the various problems and solutions are discussed.     

The Biology of the Tospoviruses

The tospoviruses are a diverse, cosmopolitan and economically important genus of plant viruses. In the recent past, interest in the tospoviruses has been rekindled with the resurgence and expansion of tomato spotted wilt virus and the appearance of new tospoviruses, including impatiens necrotic spot. This renewed interest in the tospoviruses, accompanied with the many recent advances in plant virology techniques, particularly those utilising molecular biology, have resulted in a rapid growth of our understanding of these viruses. This paper provides a review of the tospoviruses, encompassing all the major aspects of their biology, including the recent changes in the classification of the genus and current knowledge on molecular biology, vector relations, control and diagnosis.     

Nuclear Degeneration of Epidermal Cells of Senescing Soybean Cotyledons

The pattern of senescence of soybean cotyledons of intact seedlingswas characterized using interference microscopy, to measurenuclear dry mass, and nucleic acid staining and microdensito-metry,to measure DNA and total nucleic acid content of the epidermalnuclei. Nuclear dry mass, DNA, and total nucleic acid contentdeclined from 16 d after planting until the time of abscission.The effect of detaching cotyledons and floating them on wateror the growth hormones, kinetin or IAA, during the senescencephase was examined. During the time when cotyledons of intactseedlings senesced and abscised, detached cotyledons showedno symptoms of senescence. Further, there was no change in thedry mass of nuclei in epidermal cells from cotyledons floatedon water or kinetin but there was a significant increase inthe dry mass of nuclei from cotyledons floated on IAA.     

Lymphoid Cell Lines: Activation of a Latent Herpes-like Virus Particle?

SINCE the discovery¹ of the herpes-like virus particle (EBV) in cell cultures of Burkitt's lymphoma, the virus has been found in many (but not all) lymphoid cell cultures derived from patients with Burkitt's lymphoma² and other lymphoid neoplasms³ or infectious mononucleosis⁴ as well as from normal individuals⁵. The virus has also been found in some biopsies of Burkitt tumours⁶. Serological evidence has implicated it as a causal or associated agent in heterophile-positive infectious mononucleosis^{7, 8}, although its relationship to Burkitt's lymphoma is less clear. Antigenic studies suggest a relationship between the herpes-like virus and antigens detected by indirect immunofluorescence (IF) techniques in fixed cells⁹, surface antigens on viable cells¹⁰ and complement-fixing (CF) antigens in extracts of Burkitt cell cultures¹¹.     

Next-generation sequencing and metagenomic analysis: a universal diagnostic tool in plant virology

A novel, unbiased approach to plant viral disease diagnosis has been developed which requires no a priori knowledge of the host or pathogen. Next-generation sequencing coupled with metagenomic analysis was used to produce large quantities of cDNA sequence in a model system of tomato infected with Pepino mosaic virus . The method was then applied to a sample of Gomphrena globosa infected with an unknown pathogen originally isolated from the flowering plant Liatris spicata . This plant was found to contain a new cucumovirus, for which we suggest the name 'Gayfeather mild mottle virus'. In both cases, the full viral genome was sequenced. This method expedites the entire process of novel virus discovery, identification, viral genome sequencing and, subsequently, the development of more routine assays for new viral pathogens.     

Floral biology and pollen viability of parental lines of onion hybrids

Parental lines (inbred and hybrid male-sterile lines and inbred pollinators) of prospective F, hybrids from the NVRS spring-sown bulb onion breeding programme were examined to study their floral biology and aspects of pollination under glasshouse conditions. Inbreeding depression occurred in both pollinator and male-sterile inbreds in terms of reduced flower numbers per umbel and a greater proportion of defective pistils. Male-sterile and male-fertile lines differed in their stigma and style characteristics and pattern of development. At flower opening, the styles of male-sterile lines were longer and the stigmatic knob became receptive relatively sooner. The inbred male-sterile line II/3 ms appeared to have a reduced receptive area on its stigmatic knob and remained receptive for a relatively shorter period. Individual lines differed for time of flowering, nectar content and its sugar concentration, and in their effectiveness as male and female parents as judged from pollen tube growth down the style in specific pairings. Assessment of pollen viability using the fluorescein diacetate test did not correlate with assessments based on pollen grain germination and subsequent growth down the style, perhaps as a result of differential receptivity in the inbred lines tested. These results are discussed in relation to future hybrid seed production.