“GENE TRANSFER IN SECONDARY AND TERTIARY GENE POOLS” (Seminar Synopsis)

UNIVERSITY OF AGRICULTURAL SCIENCES, BANGALORE

DEPARTMENT OF GENETICS AND PLANT BREEDING

“GENE TRANSFER IN SECONDARY AND TERTIARY GENE POOLS”

Gene pools are classified into three categories: primary (cultivated species and their immediate wild relatives), secondary (related species with limited crossability), and tertiary (distant species requiring advanced techniques for gene transfer). While the primary pool allows for easy hybridization and fertile offspring, it often lacks novel traits needed for future breeding challenges. The secondary and tertiary pools serve as reservoirs for valuable genes conferring resistance to diseases, pests, drought, salinity, and other stresses, but transferring genes from them is hindered by biological and technical challenges.

Wide hybridization enables gene transfer from distant gene pools through interspecific (within genus) and intergeneric (between genera) crosses. Notable successes include triticale and raphanobrassica. However, such crosses often face barriers like incompatibility, hybrid inviability, sterility, and hybrid breakdown. To overcome these, techniques such as chromosome doubling with colchicine, embryo rescue, protoplast fusion, somatic hybridization, and ploidy manipulation are used. Additional methods like bridge crosses, reciprocal crosses, and mentor pollen aid in successful fertilization. Chromosomal manipulations such as alien addition lines, substitution lines, and Robertsonian translocations further facilitate the transfer of desirable traits. A well-known example is the 1BL.1RS wheat–rye translocation used for disease resistance.

The LrTrk gene from Triticum turgidum var. durum cv. Trinakria was transferred into wheat variety HD3086 via marker-assisted backcrossing, producing six rust-resistant near isogenic lines. Among them, HD3086+LrTrk-2 showed higher yield and is nominated for AICRP trials as a potential replacement.

Gene transfer from secondary and tertiary gene pools broadens the genetic base of crops by introducing novel traits. Advanced cytogenetic and biotechnological tools help overcome hybridization barriers, enabling sustainable crop improvement.

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REFERENCES

1. Dwivedi, S.L., Upadhyaya, H.D., Stalker, H.T., Blair, M.W., Bertioli, D.J., Nielen, S., and Ortiz, R. (2008). Enhancing crop gene pools with beneficial traits using wild relatives. Plant Breed. Rev., 30: 179-230.

2. Gupta, P.K. (2016). Cytogenetics. 1st Edition, pp. 253-270.

3. Yadav, S., Chandra, A.K., Agarwal, P., Choudhary, M.K., Bansal, S., Kumar, A., Tyagi, S., Shukla, H., Raj, N., Abrol, S., and Raghunandan, K. (2024). Marker-assisted introgression of leaf rust resistance from Triticum turgidum Cv. Trinakria to bread wheat variety HD3086. Indian J. Genet. Plant Breed., 84 (03): 323-327.