New methods of diagnosis in plant pathology – perspectives and pitfalls ¹

Abstract

As a spin‐off from fundamental molecular biological research, there has been a remarkable increase in new methods for diagnosis (i.e. detection and identification) in recent years. Because of their origin, these new methods all have in common that they use structural elements of the target organisms such as nucleic acids, lipids, fatty acids, proteins, polyamines and polysaccharides as a basis. These structural elements are either used as templates for development of so‐called probes for detection (and identification) or they are placed into man‐made patterns and used for identification/classification. The article presents the advantages and perspectives of the new methods compared with conventional ones. It may be noted that, in many studies, the specificity and reproducibility of the new methods has not been adequately treated or has even been only assumed. These features, which are closely linked with experimental and sampling error, lead to the principal pitfalls of the new methods, which are also reviewed.

Detection of a tomato strain of Parietaria mottle virus (PMoV‐T) by molecular hybridization and RT‐PCR in field samples from north‐eastern Spain

“…Therefore specific and sensitive methods are required for correct virus identification. Serological and molecular procedures have frequently been used for the detection of a wide range of plant pathogens, including viruses ( Janse, 1995;Sánchez-Navarro et al, 1998). Currently there is no commercially available antiserum to detect PMoV-T by ELISA, but in any case it will be more effective to use monoclonal antibodies taking account of the cross-reaction obtained with TSV-infected plants using the polyclonal antiserum.…”

Differentiating A and B groups of Leptosphaeria maculans, causal agent of stem canker (blackleg) of oilseed rape

“…The value of recent advances in nucleic acid technology, in particular the polymerase chain reaction (PCR), in the detection and characterization of plant pathogens, is well established, and such techniques are becoming widely adopted (Hansen & Wick, 1993;Henson & French, 1993;Janse, 1995;Putnam, 1995). Consequently, molecular characterization of L. maculans has received considerable attention, and results from several methods -including electrophoretic karyotyping, RFLP profiling, DNA sequence analysis and several PCR-based methods -provide compelling evidence that L. maculans consists of more than one species (Johnson & Lewis, 1990;Koch et al, 1991;Taylor et al, 1991;Meyer et al, 1992;Schä fer & Wö stemeyer, 1992;Xue et al, 1992;Morales et al, 1993aMorales et al, ,b, 1995Patterson & Kapoor, 1995;Voigt & Wö stemeyer, 1995;Jedryczka et al, 1997).…”

Prevalence, species composition, genetic variation and pathogenicity of clover rot (Sclerotinia trifoliorum) and Fusarium spp. in red clover in Finland

“…The advantages of these new methods are their rapidity, sensitivity and cost-effectiveness (Janse 1995). RAPD (random amplified polymorphic DNA)-PCR is one of the fingerprinting methods, which can be used for screening differences and similarities between fungal isolates without previous knowledge about their DNA sequences.…”