Title | Developing salt tolerance |
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Abstract |
Not available – first paragraph follows:
Salinity and its potential influence on plant productivity can be managed either by physically manipulating the environment in which the plant grows or by biologically manipulating the plant to reduce the harmful effects of excess salt. The concept of biological manipulation is based on the observation that salt tolerance appears to be genetically controlled and that plants vary widely in their sensitivity to high levels of salt. |
Author |
Rains, D. William : D. William Rains, Professor, Agronomy and Range Science, and Director, Plant Growth Laboratory, U.C., Davis.
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Publication Date | Aug 1, 1982 |
Date Added | Jul 17, 2009 |
Copyright | © The Regents of the University of California |
Copyright Year | 1982 |
OCR Text |
JKC Suzanne Stavarek . I . . . . . . . . as yeia , stressresistance , or numtiona qua - ity , but it may present methods to releasepre - E viously unavailable variability for such traits . F MPGE does not stand alone in plant Clearly , improvement ; integration with conventional methods is absolutely necessary . In considering agricultural applications of genetic engineering , some requirements should be mentioned that are the subjects of current and future research . ( 1 ) Cell or tissue culture systems are needed to select for the ( 2 ) Systemsmust target characteristic ( gene ) . be developed to regenerate plants from cell ( 3 ) cultures rapidly and in large numbers . Gene expression in cell cultures must also be sustained at the stage of growth in which the Selecting for salt tolerance : ( A ) Alfalfa cotyledon produces callus from cut portion . ( 6 ) A ( 4 ) Good vectors and plants will be utilized . single alfalfa cell has potential to regenerate into a complete alfalfa plant . ( C ) Cells are probes must be developed to transmit and challenged with salt in nutrient medium ; light - colored areas are living and presumably salt . identifythe desired genes . These are substan - resistant ; brown and black areas are dead . ( D ) Resistant cells , on new medium , begin to MPGE , but they are tial criteria for utilizing differentiate into plantlets . ( E ) Regeneratedalfalfa plant , when hardy enough , will be certainly not beyond the scope of plant biol - transplanted into soil for further study . ogy research . Plant cell culture techniques may be used Developing salt of to obtain salt - tolerant cell lines . This use Some opportunities lor using molec - cell cultures is based on the application of tolerance ular plant genetic engineering in mutant selectiontechniques developed in mi - plant improvement crobial and fungal systems ( see articles by Z . OTo make transfers of genes from one D . William Rains R . Sung and G . E . Jones in this issue ) . The species to another that would not be a cell general selective strategy is to produce possible with nonmolecular culture of a crop plant and to challengethese methods . OTo transfer genes at a single step , cells with an inhibitory salt concentration by Salinityand its potential influenceon plant ratherthan through repeated crosses incorporating the salt into the nutrient productivity can be managed either by physi - or backcrosses . medium in which the cells are grown . The cally manipulating the environment in which OTo transfer only the target gene , with - rare cells that can survive and divide under the plant grows or by biologically manipu - out detrimental genes linked or other - wise associated with it . these conditions are candidates for further lating the plant to reduce the harmful effects OTo transfer genes rapidly in species of biologicalman - study . By inducingthe survivorsto regenerate of excess salt . The concept with long generation times . ipulation is based on the observation that salt whole plants , it is possible to determine 0To transfer genetic information to tolerance appears to be geneticallycontrolled whether the salt tolerance observed in the plants that will facilitate new end - products . vary widely in their sensitivity and that plants selected cells is stable and transmitted geneti - OTo conserve plant genes in cloned to high levels of salt . cally . DNA gene banks . Sometimes traditional breeding methods a line In our laboratory we have obtained OTo assess genetic variation and ge - of salt - tolerant alfalfa cells by this means . cannot be used to develop salt - tolerant crops . netic relationships among species by molecular methods . The salt - selected line grows better than un - Natural genetic variability in tolerance to sa - 0 To capitalize on " spinoff " technology at a high level of salt ( 1 percent selected cells linity may be lacking or not accessible by for use in conventional gene transfer sodium chloride ) , indicating that the selec - usual breeding methods . In these cases , it is systems - for instance , tissue , cell tion isolated variant cells with an increased appropriate to apply new techniques to or protoplast culture methods . capacity for growth in the presence of high achieve this goal . 30 CALIFORNIA AGRICULTURE , AUGUST 1982
D . W . Rains examines a culture plate containing alfalfa cells growing on a high - salt medium in â?? cell city , â?쳌 where billions of cells are grown and selected for salt tolerance under light - and temperature - controlled conditions . development of recombinant DNA tech - salt . This selected line additionally displays of genetically niques opens the possibility other characteristicssuggestingthat the toler - engineering plants by introducing desired di - a true halo - ance results from a shift toward sease resistance genes from both intraspecific phytic nature . Besides tolerating high salts , and intergenic sources . Such techniques Genetic disease as evi - halophytes actually require some salt , would be immediatelyapplicableto thesetwo denced by poor growth in its absence and resistance problems and would also increase under - growth stimulation when salt is added . standing of the mechanisms of natural di - The capacity of a cell culture to regenerate David G . Gilchrist sease resistance and nonhost immunity . plants usually diminishes over time . This The major limitationto direct implementa - in cell selection pro - presents difficulties Noel T . Keen tion of this technology is that no single resis - grams , because , by the time the selection and tance mechanism has been characterized testing stages are completed , the selectedcells T h e most widely used plant disease control completely , nor have the interactive gene may fail to respond to standard regeneration method has been the incorporation of single , products been identified . Extensive physio - conditions . This was indeed the case with our usually dominant , genes for disease resis - logical information indicates that resistance 200 media alfalfa cell line . By testing some fall into two general classes , in - tance into cultivated plants . In some cases ; phenomena modifications , we developed a sequence of disease control also has been accomplished ducible and constitutive . media that enabled us to regenerate plants In the former case , resistant plant geno - by withdrawal from plants of certain domi - from the salt - tolerant cultures . The regener - types appear to recognize some feature of the nant alleles conferring vulnerability to attack ated plants could then be tested to determine invadingpathogen , which then initiatesan in - by pathogens that produce specifictoxins . By whether the salt tolerance of the cells in cul - either approach , genetic resistance affords duced defense response . This is typified by ture was carried through to the whole plant . hypersensitive necrosis.of plant cells at the the only practical control strategy in most Unfortunately , in our case , the regenerated infection site and is associated with the ac - major crops . plants were very weak and we were not able cumulation of antibiotic chemicals called Two current problemswith the use of resis - to demonstrate any increase in salt tolerance . ( 1 ) they are frequently over - phytoalexins . Recent evidence from Univer - tance genes are : Our evidence , and that from other laborator - come by new forms of the pathogen , which of California , Riverside , is consistent sity ies , indicates that our approach is sound , with the hypothesis that recognition involves appear to evolve from the original pathogen however , and we are confident that con - population by either genetic recombination resistancegene products in the form of recep - tinued efforts will produce salt - tolerant crop or mutation ; tor moleculesthat interact with specific com - ( 2 ) suitable genes conferring plants that transmit this valuabletrait to their plex cell surface carbohydrates ( elicitors ) of disease resistance often are not availablein a progeny . or genus , or they cannot be incor - the invading pathogen . The exact nature of plant species D . William Rains , Professor , Agronomy and porated into agronomically useful cultivars the pathogen genes that may determine this Range Science , and Director , Plant Growth La - boratory , U.C . , Davis . because of cross - fertility barriers . Recent unique carbohydrate structure is unknown , CALIFORNIA AGRICULTURE , AUGUST 1982 31
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