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Wheat Information Service
Number76: 53-53(1993)


Chromosomal location of the genes for vernalization response, Vrn2 and Vrn4, in common wheat, Triticum aestivum L.

K. Kato, K. Nakagawa and H. Kuno

Faculty of Agriculture, Kochi University, Nankoku 783, Japan


Although five genes are known to give spring growth habit in common wheat, their chromosomal location has been established only for three genes, namely Vrn1(5A), Vrn3(5D), and Vrn5(7B). Using monosomic series of 'Chinese Spring', Maystrenko (1980) concluded that Vrn2 and Vrn4 was located on 2B and 5B chromosomes, respectively. On the other hand, Hoogendoom (1985) suggested that Vrn gene on 5B chromosome is not Vrn4, but Vrn2. Such a confusion seems to be resulted from the fact that 'Chinese Spring' itself carries Vrn3. In other words, in F₂ population of the crosses between Vrn2 carrier and CS monosomics, winter type should segregate at 1/16 and at a few percent in non-critical and critical crosses, respectively. Accordignly it is difficult to distinguish the two types of segregation ratio, and thus careful analysis is necessary to know their chromosomal location.

From these considerations, the monosomic series of winter wheat varieties, 'Dwarf A' and 'Nanbukomugi', were used to locate Vrn2 and Vrn4, respectively. The seeds of these lines were kindly supplied by Dr. A. J. Worland, Cambridge Laboratory, UK, and Dr. K. Mukade, Tohoku National Agricultural Experiment Station, Japan, respectively.

Segregation ratio of spring and winter types fitted well to 3:1 in most of F₂ populations derived from monosomic F₁ plants of crosses between 'Dwarf A' monosomics and 'Triple Dirk(B)', which carried singly Vrn2 among five Vrn genes. On the other hand, segregation ratio didn't fit to the expected ratio in the cross with 'Dwarf A' monosomic for 5BL-7BL chromosome, winter type being much less (99:8) than expected. This result indicated that Vrn2 must be located on either 5BL or 7BL chromosome.

Similarly segregation ratio of spring and winter types was examined in F₂ populations derived from monosomic F₁ plants of crosses between 'Nanbukomugi' monosomics and 'Triple Dirk(F)', which carried singly Vrn4 among five Vrn genes. In the cross with 'Nanbukomugi' monosomic for 5D, winter type segregated much less (126:13) than expected, indicating that Vrn4 was located on 5D chromosome.


References

Hoogendoorn J (1985) The physiology of variation in the time of ear emergence among wheat varieties from different regions of the world. Euphytica 34: 559-571.

Maystrenko OI (1980) Cytogenetic study of the growth habit and ear-emergence time in wheat (Triticum aestivum L). Proc. XIV Int. Congr. Genet.1 (No.2): 267-282.

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