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生物学论文 植物病害对农业生产的主要影响

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