Molecular Markers As Tools For Identification And Introgression Of Virus-Resistant Genes

A majority of the plant viral diseases are spread by insect vectors. Control of vectors using chemicals is a common practice for management of viral diseases. Although, to prevail such situations is still impractical as high recurring costs of the pesticides. Emergence of insecticide resistant insect populations, human anxiety regarding pesticide residue and its side effects also are other concern. Hence development of virus-resistant crop plants is the need of future. In order to accelerate the current scenario of virus resistance breeding, molecular markers could function as a key tool to help and skip several generations of crossing and analysis altogether, thereby saving precious time. The researchers associated with the science of plant breeding and plant pathology has discovered reliable and rapid diagnosis techniques for many viral diseases using different molecular markers. Screening of viral disease resistance lines by marker-assisted selection (MAS) is most common technique, because phenotypic selection of virus-resistant lines is always not convenient. It has a immense importance to come across the mandate of resistance breeding, hence markers like SCAR, RFLP, RAPD, SSR, AFLP, TRAP and CAPS known for their powerful genetic association could be used to supply complementary information to the classical genetic analyses. In resistance breeding programme gene tagging of particular trait is a necessary object for map based gene cloning and MAS. But mapping of genetic linkage is a time consuming procedure. In recent years, it is possible to identify markers directly without drawing any genetic linkage map. Markers based on nucleotide-binding and leucine-rich repeat domain (NB-LRR) is an advanced tool for identification of disease resistant genes. Markers based on molecular genetics can be used to determine the monogenic or polygenic disease resistance in crops which could provide durable resistance to wide range of pathogens. The gene pyramiding technique in crops is the best way for developing durable resistance (multigenic resistance) against multiple diseases. Based on molecular markers, identified segregating population in crops with viral disease resistance is needed to be confirmed against challenged viral inoculums either in controlled environment or in natural field conditions.