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Hybrid necrosis in wheat: evolutionary significance or potential barrier for gene flow?

Vikas, V. K., Tomar, S. M. S., Sivasamy, M., Kumar, Jagdish, Jayaprakash, P., Kumar, Arun, Peter, John, Nisha, R., Punniakotti, E.
Euphytica 2013 v.194 no.2 pp. 261-275
Triticum aestivum, dominant genes, gene flow, germplasm, hybridization, hybrids, models, necrosis, parents, pedigree, prediction, wheat, India
One hundred and four released varieties of bread wheat (Triticum aestivum L ssp. aestivum) in India were crossed to two T. aestivum L ssp. aestivum testers, namely, C306 (Ne (1) Ne (1) ne (2) ne (2) ) and HD2329 (ne (1) ne (1) Ne (2) Ne (2) ) to determine the frequency and distribution of genes for hybrid necrosis present in them. Sixty-seven varieties (65.4 %) showed the presence of Ne (2) gene and only eight varieties (7.7 %) had Ne (1) gene in their background. Twenty-nine varieties (27.9 %) were non carrier (ne (1) ne (1) ne (2) ne (2) ) for both the genes. Most of the Ne (1)-carriers are of Indian origin and their pedigree revealed the involvement of landraces and old varieties as parents. Predominance of Ne (2) gene in Indian varieties happened after the introduction of semi-dwarf Mexican wheat varieties, which are mostly Ne (2) carriers and also due to the extensive and continuous use of germplasm from Mexican and European origin in the hybridization programme. Moreover varieties with Ne (2) gene is selected for their linked beneficial traits mainly rust resistance genes. The phenomenon of hybrid necrosis is one among the post zygotic barrier speciation process which acts as a barrier for either intra or inter specific gene flow. The genetic architecture of hybrid necrosis in wheat is simple following the minimal predictions of the Bateson-Dobzhansky-Muller model. Widespread occurrence of dominant genes for hybrid necrosis in Indian varieties is of great concern to wheat breeders as it often interferes in the choice of elite parents and imposes restrictions on the productivity of crosses.