Tolerance crops

There are several aspects of different environmental stresses that either have common features or the plant responses or adaptations to those stresses may have common components or indicate general principles. It is an objective of this volume to identify such features where they exist so as to help in the development of stress-tolerant crop plants by making the best use of the newer techniques of molecular biology. Particular examples will be discussed in more detail in succeeding chapters. 

Lawton, M. (2003). Management of Herbicide Tolerant Crops and Future Research, Canadian Food Inspection Agency, Plant Products Directorate, Plant Biosafety Office Technical Workshop on the Management of Herbicide Tolerant (HT) Crops Report. www.inspection.gc.ca/english/plaveg/bio/consult/herbtolrepe.shtml 7. Accessed June... 

Although arsenic is not an essential plant nutrient, small yield increases have sometimes been observed at low soil arsenic levels, especially for tolerant crops such as potatoes, com, rye, and wheat (Woolson 1975). Arsenic phytotoxicity of soils is reduced with increasing lime, organic matter, iron, zinc, and phosphates (NRCC 1978). In most soil systems, the chemistry of As becomes the chemistry of arsenate the estimated half-time of arsenic in soils is about 6.5 years, although losses of 60% in 3 years and 67% in 7 years have been reported (Woolson 1975). Additional research is warranted on the role of arsenic in crop production, and in nutrition, with special reference to essentiality for aquatic and terrestrial wildlife. 

Watkinson, A.R. Freckleton, R.P. Robinson, R.A. Suthaland, W.J. (2000) Predictions of biodivasity response to genetically modified habicide-tolerant crops. Science, 289,1555-7. 

The metabolism of atrazine and a series of 2-chloro-.v-lriaz.ines were reported by Lamoureux et al. (1972) in excised leaf or shoot tissue of barley, corn, sorghum, and sugarcane. The authors found that the primary route of metabolism was the displacement of the 2-chloro group with glutathione or 7-glutamylcysteine. The overall rate of metabolism in susceptible barley was much slower than in tolerant crops. 

Triazine Selectivity in Crops and Weeds Triazine-Tolerant Crops... 

Padgette, S.R., X. Delannay, L.D. Bradshaw, B.H. Wells, and G. Kishore (1995). Development of glyphosate-tolerant crops and perspectives on the potential for weed resistance to glyphosate, p. 154. In De Prado, R., Garcia-Torres, L., and Jorrin, J., eds., International Symposium on Weed and Crop Resistance to Herbicides. Cardoba, Spain Cardobesa de Impresiones Graficas, SL. Abstract, 92. 

Acetochlor Control of most annual grasses, some broadleaf weeds. Tolerant crops include corn, soybeans, peanuts, sugarcane. 2,953 rat acute oral... 

Lauchli A., Grattan SR. Plant growth and development under salinity stress. Jenks MA, Hasegawa PM. Jain SM. (ed.) Advances in Molecular Breeding toward Drought and Salt Tolerant Crops. Dordrecht, Netherlands, Springer 2007,1-32. 

Further improvements in herbicidal activity were obtained by introducing an alkoxy function at the 5-position of the aromatic ring (Table IV) (4). The triazin-3-one with propynyloxy at this position was the most effective, providing >80% weed control at 0.031-0.062 kg/ha. Soybeans were the most tolerant crop but the difference in weed control rates and the lowest rate for minimum soybean injury may be marginal. 

Lipids. Dinitroaniline herbicides are effective on small-seeded, lipid-poor species. Hilton and Christiansen (7) examined the level of seed lipid and the susceptibility of a plant to trifluralin and found a good correlation between the two. These authors concluded that the herbicides would be compartmentalized into the lipid bodies of the seed and away from the growing tip of the plant. Upadhyaya and Nooden (8) even found that there is a differential between susceptible and tolerant species in the uptake of oryzalin into the membrane system, indicating that more than the seed lipids may be involved in determining dinitroaniline sensitivity. Chernicky (9) investigated the possibilities that alterations in the amount of lipid is involved in the resistance of Eleusine to dinitroaniline herbicides. Both susceptible (S) and resistant (R) biotypes had less total lipid than tolerant crop species and even most sensitive weed species. The S biotype had actually 36% more total lipid in the roots than the R biotype (a result opposite to what one would expect if higher lipid content correlates dinitroaniline resistance). 

The increasing use of nonselective herbicide products on herbicide-tolerant crops accompanied by the concerns on the safety of adjacent nontolerant crops or noncropped environment. 

The need to produce stress-tolerant crops was evident even in ancient periods... 

However, efforts to improve crop performance under environmental stresses have not yet been very fruitful, mainly because the fundamental mechanisms of stress tolerance in plants remain to be completely understood. A genetic approach to the development of specific stress-tolerant crop varieties requires as a pre-requisite the identification of key genetic determinants of stress tolerance-related genes or quantitative trait loci (QTL). The existence of salt-tolerant plants (halophytes) and differences in salt tolerance between genotypes within salt-sensitive plant (gly-cophytes) species clearly indicates that there is a genetic basis to salt response. 

White RH, Engelke MC, Morton SJ, Johnson-Cicalese JM, Ruemmele BA. Acremonium endophyte effects on tall fescue drought tolerance. Crop Sci 32 1392-1396, 1992b. 

In mono- and dicotyledonous tolerant crop plants symptoms caused by EPTC are similar though milder, but tolerant plants outgrow the injury in the later stages of growth. 

Sometimes a moderately saline soil (EC < 25 dS/m), comprised of coarse or medium structure, can be reclaimed to support salt-tolerant crops, by adding up to 10% low salt manure. The addition of organic matter increases the cation-exchange capacity of the affected soil. A 10% treatment can absorb up to 8000kg of salt per hectare (Deuel, 1999). 

Yamagnchi, T., and E. Blumwald. 2005. Developing salt-tolerant crop plants challenges and opportnnities. Trends Plant Sci. 10 615-620. 

Table II. Toxic Boron Concentrations of Saturation Extracts for Sensitive, Semitolerant, and Tolerant Crop Species ...

Perhaps the most widely accepted irrigation water criteria are those published in 1954 by the staff of the U. S. Salinity Laboratory (33). Criteria for boron include possible limits for four classes of irrigation waters according to sensitive-, semitolerant-, and tolerant-crop species. More recently, Wilcox (39) published a modified set of critical concentrations which are somewhat more fiexible in that fewer categories are involved. He proposed the following for irrigation waters ... 

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