Resistance to plant viruses: Obtaining genes by non-conventional approaches

Abstract

Plant viruses cause considerable losses to crops and none of the three current approaches to disease control are likely to give the long-term answer . The new concept of non-conventional protection, in which the expression of a viral or virus-related sequence in the plant genome interferes with the virus infection cycle, holds considerable promise for designing new resistance or protection `genes' . A series of targets in the viral genome is identified and a range of mechanisms for attacking those targets is discussed . There are several current systems which have been proved to give protection, at least to a certain extent, and many systems which are being researched upon for the future . Some of these are described to give a picture of the current situation and of the thinking for the future . The problems of field deployment of the transgenic plants are discussed, especially those associated with the risk to the environment . Various questions which molecular biologists and plant breeders will have to consider include what are desirable characters to have in protection `genes' and how these new `genes' should be deployed .

Variation in the genome of rice tungro bacilliform virus: molecular characterization of six isolates

“…One of the objectives of studying the molecular organization of RTBV is to gain information in order to develop strategies for non-conventional approaches to resistance (see Hull & Davies, 1992;Hull, 1994) …”

Resistance and Tolerance to Barley Yellow Dwarf in Cereals

“…The target genes would be those coding for coat protein, proteases and replicases, or control sequences involved in gene replication or gene expression. The non-conventional genes inserted in the plant could be genes from the virus itself, artificial genes or sequences that interfere with the target (Hull, 1994). Approaches based on pathogen-derived resistance, including coat protein mediated protection, expression of a coding region embedded in the replicase, use of antisense RNAs that are the complement of the plus-or minus-sense template of the virus had been used successfully in plants (Scholthof et al, 1993).…”

Genetic Defense Approaches against Begomoviruses

“…[77] . In the early 90s, the above mentioned phenomenon was tested by many researchers upon various begomoviruses through transformation and expression of several least aggressive viral particles [78][79][80][81][82] . as secondary transformants [73] .…”