Authors: Anurag Tripathi1, Jeet Ram Choudhary2, Sarita3, Nitish Ranjan Prakash2
2Indian Agricultural Research Institute, New Delhi-110012 India.
1GBPUA&T, Pantnagar, uttrakhand-263145 India
3RCA, MPUAT, Udaipur-313001 India.
*Corresponding author email: jrchoudhary1993@gmail.com
India is the second largest producer of wheat in the world after China, with a production of 80.6 mt. (2008-09). In 2020, expected demand of wheat is to be around 109 mt. This task of achieving target needs sincere efforts in view of biotic and abiotic stresses. Among biotic stresses, losses incurred due to rust infection are enormous, eg. yield losses from severe leaf rust epidemics (s) are estimated around 40% and losses due to stem rust and stripe rust may go even up to 100% ( Huerta-Espino et.al, 2010).
Rusts are one of the most important diseases of wheat ( Triticum aestivum) worldwide. The use of resistant wheat cultivars is considered the most economical and environment-friendly approach in controlling the disease. To combat rust infection, wheat breeder, geneticists and pathologists have transferred resistance genes in cultivars. Several genes that provide resistance against rusts have been identified and catalogued. Among them many resistance genes transferred from common genome (AABBDD) of hexaploid (2n = 6x = 42) wheat, whereas many others have been introgressed from related species and genera such as Agropyron and Secale etc. and these are effective world over (Tomar and Menon, 2001). Effective genes that provide resistance against rusts in wheat plant are bred through commonly practiced breeding procedures, where as, alien segments are usually transferred by backcrossing.
Breeding for disease resistance is an effective approach to control diseases as long as sufficient genetic variation for resistance is available. Gene pyramiding, a breeding procedure of bringing together more than one resistance gene into one desirable genetic background is useful technology to combat rust infection. The pyramiding of effective genes through conventional techniques involving phenotype based selection criteria is of course time consuming and laborious but the availability of genetic information, reaction pattern against individual races/pathotypes of rusts in seedling and adult plant stages, genetic linkages are helpful and valuable techniques that facilitate gene pyramiding through conventional methods. Though this can be achieved by pyramiding effective resistance genes conventionally (Tomar et al. 2006). Sivasamyet al. (2009) pyramided two linked genes namely, Lr19/ Sr25 and Sr36/Pm6 by of backcrossing into fifteen bread wheat cultivars. However, it is difficult to monitor in the field due to the inability to distinguish the expression of individual resistance genes or due to lack of availability of virulence in the pathogen to differentiate the genes.
With the advent of molecular marker technology it is now possible to tackle such complex problems. DNA-based molecular markers have several advantages over the traditional phenotype based selection especially when disease-escaped susceptible plants are likely to be confused for resistant plants. Molecular markers can be used for MAS to improve the efficiency of selection in plant breeding because the environment does not affect the expression of molecular markers. One Agropyron elongatum derived dominant seedling resistance gene (Lr24) and one recessive adult plant resistance (APR) gene (Lr48) for leaf rust resistance, were pyramided together employing MAS with SCAR marker SCS1302607 tagged to the gene Lr24 and two RAPD markers flanking the gene Lr48, S3450 and S336755 in wheat.( Samsampour et al. 2009).
References:
- Huerta-Espino, J., Singh, R. P., German, S., McCallum, B. D, Park, R. F., Chen, W., Bhardwaj, S. C. and Goyeau, H. 2010. Borlaug Global Rust Institute, Technical Workshop, St. Pertersburg, Russia May 30-31.,pp 112.
- Tomar, S .M. S. and Menon, M. K. 2001. Genes for resistance to rust and powdery mildew in wheat. Annual report. I. A. R. I., New Delhi. pp 152
- Tomar, S. M. S., Menon, M. K., Bojan, S. and Sinha, V. C. 2006. Exploitation of useful genes for rust and powdery mildew resistance in wheat through conventional method.Indian J.Res. 76(12): 721-725.
- Samsampour, D., Maleki Zanjani, B., Singh, A. K., Pallavi, J. and Prabhu, K. V. 2009. Marker Assisted Selection to Pyramid Seedling Resistance Gene Lr24 and Adult Plant Resistance Gene Lr48 for Leaf Rust Resistance in Indian Wheat. Indian J.Genet .69(1) :1-9
- Sivasamy, M., Vinod, Sushma, T., Tomar , R. S., Singh, B., Sharma, J. B., Tomar, S. M. S. and Chand, Suresh. 2009. Introgression of useful linked genes for resistance to stem rust,leaf rust and powdery mildew and their molecular validation in wheat ( Triticum aestivum L.). Indian J. Genet. 69(1): 17-27.
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