Title | Isozymes in plant breeding |
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Abstract |
Not available – first paragraph follows:
Isozymes are multiple molecular forms of an enzyme derived from a tissue of an organism. They are usually separated when an electric charge causes their migration through a gel, and they are visualized when the gel is placed in a solution of the proper substrate for the enzyme and the end product of the reaction is stained. This procedure results in discrete bands, whose positions in the gel are determined by the charge and molecular weight of the isozymes. The preparation is usually a simple extract, sometimes just the unmodified juice obtained by crushing the plant sample. |
Author |
Rick, Charles M. : Charles M. Rick, Professor, Vegetable Crops, 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 |
is that they are sometimeslinkedto important have been found . Thus we can identify resis - economictraits . Likegenesfor any character , tant plants at a much earlier stage , distinguish those coding for isozymes occupy specific resistant from susceptible plants more reli - loci on the chromosomes and are therefore ably because testing against the parasite is subject to the linkage relationship . That is , often beset with technical problems , and dis - the closer two genes are to each other on the tinguish between homozygous ( Mi / Mi ) and chromosome , the stronger is their tendency ( Mi / + ) plants - a task that heterozygous to be inherited together . Linkages between otherwise requires progeny tests for nema - isozyme markers and important economic tode susceptibility . lsozymes in traits are being exploited in tomatoes , since Linkages with isozyme loci can also assist the lack of effect in breeding programs dealing with quantita - of isozymes on appearance plant breeding tive characteristics ( such as earliness or and performance renders them superior to the customary marker genes used for this yield ) . In progenies segregating simultane - Charles M . Rick ously for such metric traits and isozymes , we purpose . can estimate the minimum number of genes One example is a remarkably tight linkage determiningthe metrictraits , localizespecific ( Aps - I ) between an acid phosphatase locus Isozymes are multiple molecular forms of metric genes by tests with two or more linked and the gene for resistance to root - knot ne - an enzyme derived from a tissue of an organ - ( Mi ) in tomato . The Mi gene was isozyme markers , and detect the presence of matodes ism . They are usually separated when an elec - discovered in a wild tomato relative , Lyco - plus or minus modifier genes . There is evi - tric charge causes their migration through a dence that selection for linked isozyme persicon peruvianum , and was invariably as - gel , and they are visualized when the gel is markers might be more reliable in improving sociated with a clearly defined variant acid placed in a solution of the proper substrate a metric character than selectionfor the char - L . peru - phosphatase band . Hybrids between for the enzyme and the end product of the re - vianum and cultivated tomato , L . esculen - acter itself . Another application is the more action is stained . This procedure results in tum , have both parental bands and an inter - rapid elimination of undesired wild - parent discrete bands , whose positions in the gel are mediate â?? hybrid â?쳌 band in the mid - position . traits that can result from intense selection determined by the charge and molecular against the wild - type form All three possible genotypes can be detected of the isozymes weight of the isozymes . The preparation is when genes are introduced into a cultivated of stems , roots , or from simple preparations usually a simple extract , sometimes just the leaves of plants of any stage . To date , almost a wild relative . plant by crossing with unmodified juice obtained by crushing the no exceptions to complete association be - Charles M . Rick , Professor , Vegerable Crops , plant sample . U.C . , Davis . Mi tween the slow acid phosphatase band and Since enzymes are coded by genes , the method has the great advantage of revealing gene activity much more directlythan do the end products of the familiar structural and physiological characters . In hybrid pro - genies , the segregation of isozymes , as detected by by the band patterns , determines which bands are variants corresponding to a particular geneticlocus ( that is , a position on a chromosome ) and which belongs to other loci . Isozymes permit unequivocal identifica - tion of nearly all genotypes . In contrast to the segregation of classical structural / physiolog - ical characters ( tall vs . dwarf , early vs . late ) , for which dominance and gene interaction seldompermit direct genotypedetection , this of iso - can be accomplished by examination zyme banding patterns , whether for alleles at one locus or many . The method is rapid , economical , and accurate , and the analysis ApS - 1 : + I1 + I1 + I + + I1 111 + / I + I + can be made for nearly all loci in earlygrowth Mi : + lMi + lMi + I + + lMi MilMi MilMi + lMi + I + stages , sometimes even in the seed itself . Nematode Resis . Resis . Resis . Resis . Susc . Resis . Susc . Resis . Isozyme analysis has been used with a number of cultivated plants to determine the degree of inbreeding , resolve problems in tax - Segregation of acid phosphatase isozymes ( APS - 7 ) as seen in onomy , study chromosome pairing in poly - starch gel banding patterns of eight plants in F2segregation . ploids , and identify cultivars . Isozymes can Below that is corresponding + / Mi segregation and susceptibility so that it could be in - be bred into a cultivar or resistance to nematodes . Resistant class includes both MiIMI ( homozygous or true - breeding resistant ) and + / Mi ( heterozygous controvertiblyidentifiedfor legal purposes - or segregating resistant ) . a possible form of control for patented vari - eties . One of the most useful aspects of isozymes 28 CALIFORNIA AGRICULTURE , AUGUST 1982
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