The following points highlight the four main applications of RFLP marker in plants. The applications are: 1. Linkage Construction 2. Disease Management 3. Analysis of Somaclonal Variation 4. Prediction of Genetic Distance.
Application # 1. Linkage Construction:
Restriction fragment length polymorphism facilitated in the construction of linkage maps of any genotypes and genes linked to certain specific agronom characters have been successfully mapped by RFLP markers. In conventional method, genetic mapping is generally accomplished during crossing over recombination process by F1 plant.
The action of genes after looking at the flower colour, plant height etc. and those methods are considered to be time consuming. Besides, the inheritance pattern of RFLP marker, segregate exactly and follow mendelian rule. Construction of RFLP genetic map involves series of steps. After the selection of a parent plant by wide range of survey DNA is isolated and digested with restriction enzymes and screened for polymorphism.
In the next step, production of mapping population is accomplished by crossing selected parent plant to produce F1 plants. Consequently F1 plants are selfed to produce F2, which can be screened for segregation of RFLP or back crossed to one of the parent. The mapping populations are available from remnant seeds from previous cases.
This would pave the speed up process without being crossed in the final step. Once population mapping is procured, DNA is extracted from each individual plant in the population. It can be presumed that the chromosome of each plant in the population contains wide array of parental chromosome segments.
Mapping population is followed by scoring RFLP in the individual plants of mapping population. The data obtained from the scoring of mapping population and information from the library is used to construct linkage map.
Application # 2. Disease Management:
RFLP technique has been implicated in disease management by detection of plant-pathogen. RFLP analysis has been used to distinguish Sclerotinia species. Probes are obtained from nuclear and mitochondrial genes including ribosomal RNA genes. Probe from Neurospora crassa which helps in distinguishing of two or seven species of Sclerotinia.
RFLP based on VNTR from genomic library of Pithium has been used to identify plant pathogen, Pithium. RFLP marker helps in the transfer of certain fruit quality trait from wild into cultivated crops.
Tightly linked RFLP marker for sucrose accumulator gene has been transferred into tomato (Lycopersicum esculentum) from wild tomato (Lycopersicum chmielewski). RFLP marker has been identified for genes conferring resistance to the root cyst nematode in potato.
Bentolina (1991) identified tight linkage of a RFLP marker to the Ht1 gene of maize that confer resistance to the fungal pathogen Helminthosporium turcicum by four pairs of near isogenic lines. Genetic dwarfism caused by gene has been mapped with the help of RFLP markers on the long arm of chromosome in case of barley. RFLP is used to investigate variation in mitochondrial genes.
Application # 3. Analysis of Somaclonal Variation:
Genetic variation can be induced by invitro culture which is otherwise known as somaclonal variation. Tissue culture derived plants are prone to genetic alteration or deliberatively by induced in vitro. RFLP molecular markers are potential tool in the detection of genetic variation.
Extent of genetic variation is required to know before the introduction of single gene into the plant. If a degree of genetic variation is high then it is useful tool for plant breeders rather than for commercial release.
Application # 4. Prediction of Genetic Distance:
Increased performance of hybrid crops heterosis is due to the genetic distance between the parent plants used in cross. Molecular markers like RFLP can be efficiently used to estimate genetic distance between possible parents.
Assessment of genetic diversity in plant genetic resource collections provides better management when space and resources are constraints. RFLP molecular method can be employed to distinguish short day onions from long day (which is otherwise difficult to identify). Identification and preservation of short day onions is indispensable because of its high genetic diversity in nature.