Resistance trait

Friesen, L.F., Nelson, A.G. and Van Acker, R.C. (2003). Evidence of contamination of pedigreed canola (Brassica napus) seedlots in western Canada with genetically engineered herbicide resistance traits . Agron J, 95, 1342-1347. 

Polyoxins are used in the control of several pathogens, notably sheath blight of rice (Rhizoctonia solani). Polyoxin is specific to Alternaria, Botrytis, and powdery mildew. Differences in activity between members of the polyoxin group probably reflect dissimilar uptake characteristics, which are governed by specific peptides. Different peptides may limit polyoxin activity at the level of the uptake mechanism and may also determine their resistance traits. 

Escape Shorter crop growth period and/or early ripening to be able to avoid the critical infestation period, or to have enough yield before the infestation becomes too severe (potato/late blight onion/downy mildew carrot/carrot fly) One or more monofactorial and multifactorial, durable resistance traits against pest and disease affecting yield and/or quality (scab/apple, late blight/potato, lettuce/downy mildew, yellow and brown leaf rust/wheat) weed competition by an allelochemical ability... 

Plant Agriculture transfer of stress-, herbicide-, or pest-resistance traits to crop species, development of plants with the increased abilities of photosynthesis or nitrogen fixation, development of biological insecticides and nonice nucleating bacterium. 

Sprague et al. (1997a), however, found that of five imazethapyr-resistant biotypes of common cocklebur, only four of these biotypes were also resistant to imazaquin. Ohmes and Kendig (1999) studied the crossing of ALS-cross-resistant and susceptible biotypes of common cocklebur and concluded that the cross-resistance trait is dominant to semidominant. In all cases, the resistance exhibited at the whole plant level was associated with an insensitive ALS enzyme. 

Bacteria can obtain the various types of resistance mechanisms described previously by undergoing modifications in their genetic constitution. Many bacteria simply inherit their resistance genes from their forerunners. In addition, genetic mutations can occur that can confer a new trait. For example, it has been estimated that bacteria undergo spontaneous mutation at a frequency of approximately 1 in 10 cells. These mutations can confer resistant traits to the subsequent progeny. Mutations are believed... 

The selection of transformed cells is achieved using a conferred selectable trait, most commonly antibiotic resistance. Only transformed cells with the conferred resistance trait are able to survive and reproduce. However, the use of antibiotics as a media component for commercial protein production is problematic for at least two reasons. First, residual antibiotic would be a highly undesirable contaminant in the final product. Second, the recurrent use of antibiotics increases the likelihood that antibiotic-resistant pathogen strains will develop. Recent studies indicate that antibiotic selection is not necessary during every passage (or generation). 

The Jerusalem artichoke and other members of the sunflower family display a profusion of trichomes that often give the plant a very abrasive surface texture (Seiler, 1981). Trichomes are thought to function in part as a component of the herbivore defense system of the plant. In sunflower, introgression of biotic resistance traits is thought to have been important in adaptation (Whitney et al., 2006). The Jerusalem artichoke has at least four types of trichomes that differ in location, size, and density (Figure 4.5). 

Whitney, K.D., Randell, R.A., and Rieseberg, L.H., Adaptive introgression of herbivore resistance traits in the weedy sunflower Helianthus annuus, The American Scientist, 167, 794—807, 2006. 

Genetic. The differences between many susceptible and resistant cultivars are the abilities of the latter to appropriately respond quantitatively in time and in space to infection, rather than qualitative differences in biochemical pathways. This type of genetic resistance may be considered a form of an endogenous constitutively sensitized state. Genetic sensitization of a cultivar requires both a source of appropriate germplasm and a method of effective transfer and incorporation of the genetic material into the recipient cultivar. Both requirements cannot always be met. Furthermore, undesirable traits often accompany desired resistance traits. This very important area of plant sensitization, broadly construed, lies beyond the scope of this paper. 

Figure 10 shows, in considerably more detail, the sequence of mutagenesis and selection which has been actually used to develop herbicide resistant lines. Calli were initiated from a healthy alfalfa plant. After 4-8 weeks, these calli were broken up into suspensions, and either treated with a mutagenizing agent or screened simply by selection for spontaneous mutations. After either procedure, the selected lines, i.e., the lines which survived exposure to the herbicide, were then regenerated, and the plants were evaluated in a number of schemes. In addition, plants selected at the cellular level for resistance were recycled through the entire system of mutagenesis and selection to enhance the desired resistance trait. 

Heterogeneity in the tumor cell population, promoted by genetic instability and ensuring the adaptive survival of a cell subpopulation which defines a drug-resistant trait... 

Fore recently a comparable enhanced inhibition in resistant strains has been observed with aryloxadiazolone anticholinesterases (38). A second promising example is the discovery that some natural and synthetic isobutylamides are selectively toxic against houseflies that carry the super-kdr resistance trait (39). This gene causes an alteration in the sensitivity of the site of action for DDT and pyrethroids and is a major threat to the continued efficacy of synthetic pyrethroids in many of their applications. 

Peanut phytoalexins appear to be involved in resistance to drought-induced preharvest aflatoxin contamination of immature peanuts. Mature peanuts are considerably more resistant to environmentally-induced preharvest aflatoxin contamination of peanuts than are immature peanuts. The mechanism of this latter resistance is unknown. The identification of this resistance mechanism and other resistance may provide one approach to subsequent use of biotechnology to incorporate field resistance traits into commercially acceptable varieties. Biotechnology may also be a valuable approach to exploiting genetic resistance to preharvest aflatoxin found in wild species that have evolved in an arid environment. 

Inheritance of the Insect Resistance Trait. Copy numbers or the T-DNA inserts in transgenic plants were determined using Southern blotting. Plants expressing highest levels of B.t. protein contained around 5 copies of T-DNA. From one such plant, 15 F1 progeny were assayed and they all exhibited 100% insect killing. 

The genetic basis of insecticide resistance is not well understood. Many genes for resistance traits have been mapped to chromosomes of the house fly, Musca domestica (3.4). Drosophila melanogaster (78), and mosquitoes, Aedes aeqypti and Culex quinquefasciatus (5.6). In some cases, the expression of the biochemical... 

The sunflower crop can suffer from a number of diseases. The commonly known diseases are downy mildew, rust, verticillium wilt, scelerotinia wilt, head rot and phomposis. Plant pathologists have identified a number of genes in wild sunflower varieties that can provide resistance to these diseases in the developed hybrids. However, no single gene can offer the resistance to all of these diseases. Researchers are continuously working to incorporate improved resistance traits in the hybrids. 

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