生物学论文代写 植物病害对农业生产的主要影响
Strawberry along with other species within the Rosaceae family has suffered from a dearth of molecular genetics study as compared to the grasses and major horticultural crops like tomato, grape and citrus. Molecular-marker technologies have developed very rapidly in the last decade; however octoploid genetic structure of commercial strawberry makes it difficult to associate molecular markers with disease resistance genes. Relatively few reports of the molecular cloning of putative resistance genes have been appeared in strawberry. Recently mapping RGA in diploid and octopolid strawberry contains the conserved motifs characteristic of NBS-LRR R genes; 28 of them contained uninterrupted ORFs. All the strawberry RGAs detected were closely related to sequences of known R genes and RGAs from other species. Thus, some of them may encode resistance gene products of unknown specificity.(2004). The availability of these markers has greatly facilitated genetic analyses and the utilization of tagged resistance genes in resistant cultivar development, and it is even allowing the molecular cloning of resistance genes for transfer into desirable cultivars by genetic transformation and develop transgenic disease resistance plants,
Plant breeders have long recognized the importance of resistance genes for
preventing disease in crop plants. Many of these genes have now been found to
encode effector‑triggered immunity (ETI) receptors, and we know that pathogens
can evolve to overcome these genes through loss or alteration of the effectors
that are recognized. The careful deployment of resistance genes in crop plants,
particularly by using multiple effective receptors in combination and by
selecting target effectors that have crucial virulence functions, should allow
more durable resistance.
Many nucleotide‑binding (NB)‑leucine‑rich repeat (LRR) genes have now been
cloned, and this can facilitate their application in agriculture either through
conventional breeding approaches, in which the cloned sequences are used as
molecular markers, or through transgenic means. Widespread genome
sequencing of plant pathogens is now yielding long lists of effector proteins that
could be recognized by plant immune receptors, and these can now be screened
against wild relatives of crop plants to identify new sources of resistance. This
approach has been useful already in identifying new sources of resistance to the
potato blight pathogen Phytophthora infestans in wild potatoes120. Pathogenassociated
molecular pattern (PAMP)‑triggered immunity (PTI) receptors are
typically not variable within species and thus have not contributed widely to
traditional breeding efforts. However, the transfer of these receptors among
species has tremendous potential to deliver durable resistance, as the recognition
components are highly conserved among pathogens. Although pathogens that
are adapted to a particular host plant may be adept at suppressing the pattern
recognition receptors (PRRs) of that host, their effectors might not recognize
PRRs from other host plants. For instance, the Arabidopsis thaliana EF‑Tu receptor
occurs only in the Brassicaceae family, and transfer of this gene into tomato
provided good resistance against various bacterial pathogens121.
生物学论文代写 植物病害对农业生产的主要影响
